The 'Battle of Britain' was a strategically important air campaign in which the Royal Air Force and the Royal Navy’s Fleet Air Arm defended the UK against major attacks by the German air force (10 July/31 October 1940).

The first major military campaign fought entirely by air forces, the battle was recognised by the British as lasting from 10 July to 31 October 1940, which overlaps the period of large-scale night attacks generally known as 'The Blitz', which took place between September 1940 and 11 May 1941. In Germany the two episodes are regarded as a single campaign lasting from July 1940 to May 1941 and including 'The Blitz'.

The primary objective of the German forces was to compel the UK to agree to a negotiated peace settlement and, failing this, so weaken the British air defences that the Germans' proposed 'Seelöwe' invasion of the UK would be materially facilitated. In July 1940, the German air and sea blockade of the UK began, with the Luftwaffe targeting mainly coastal-shipping convoys, as well as ports and shipping centres such as Portsmouth. On 1 August, the Luftwaffe was directed to achieve air superiority over the RAF, with the aim of incapacitating Air Chief Marshal Sir Hugh Dowding’s RAF Fighter Command. Some 12 days later, the emphasis of the German air attacks was shifted to RAF airfields and infrastructure. As the battle progressed, the Luftwaffe also targeted factories involved in aircraft production and strategic infrastructure. Eventually, it employed terror bombing on areas of political significance and on civilians.

The Germans had rapidly overwhelmed France and the Low Countries in 'Gelb' and 'Rot' (iii), leaving the UK to face the threat of invasion by sea. The German high command appreciated the manifest difficulties of a seaborne attack while the Royal Navy controlled the English Channel and the North Sea. On 16 July, Adolf Hitler ordered the preparation of 'Seelöwe' as a possible amphibious and airborne assault on the UK to follow once the Luftwaffe had gained air superiority over the English Channel and degraded the capabilities of RAF Fighter Command. In September, the night raids of Air Marshal Sir Charles Portal’s RAF Bomber Command disrupted the German preparation of converted barges, and the Luftwaffe’s failure to overwhelm the RAF forced Hitler to postpone and eventually to cancel 'Seelöwe'. The Luftwaffe proved unable to sustain daylight raids, but its continued night-bombing operations on British targets became known as 'The Blitz'.

Germany’s failure to destroy the UK’s air defences in order to force an armistice (or even an outright surrender) was the first major German defeat of World War II, and was thus a crucial turning point in the conflict. The 'Battle of Britain' takes its name from the speech given by Prime Minister Winston Churchill to the House of Commons on 18 June, which included the words 'What General Weygand called the 'Battle of France' is over. I expect that the 'Battle of Britain' is about to begin.

Strategic bombing during World War I introduced the concept and execution of air attacks intended to panic civilian targets and led in 1918 to the merger of the British army and navy air services into the Royal Air Force. Its first Chief of the Air Staff, Major General Sir Hugh Trenchard, was among the military strategists in the 1920s, such as Giulio Douhet, who saw air warfare as a new way to overcome the bloody stalemate of trench warfare. Interception was expected to be nearly impossible as fighters were not significantly faster than bombers. The slogan of the protagonists of strategic air power was that the bomber will always get through, and that the only defence was a deterrent bomber force capable of delivering an equivalent retaliation. Predictions were made that a bomber offensive would quickly cause thousands of deaths and civilian hysteria, leading to capitulation. However, widespread pacifism following the horrors of World War I, combined with the notion that no major conflict was likely, served to create a reluctance to provide resources.

Germany was forbidden a military air force by the 1919 Treaty of Versailles, and therefore adopted the practice of clandestine training of air crew by means of civilian and sport flying. Following a 1923 memorandum, the Deutsche Luft Hansa airline developed designs for 'transport' aircraft such as the Junkers Ju 52, which could indeed carry passengers and freight, but also be readily adapted into a bomber. In 1926, the secret Lipezk fighter pilot school began training Germans in the USSR in exchange for German aid to the USSR in matters such as technical and industrial aid. Erhard Milch organised rapid expansion, and following the 1933 Nazi accession to power, his subordinate Robert Knauss formulated a deterrence theory incorporating Douhet’s ideas and Admiral Alfred von Tirpitz’s 'risk theory'. This proposed a fleet of heavy bombers to deter a preventive attack by France and Poland before Germany could rearm fully. A 1933/34 war game indicated a need for fighters and anti-aircraft protection as well as bombers. On 1 March 1935, the Luftwaffe was formally announced, with Generalleutnant Walther Wever as its chief-of-staff. The 1935 Luftwaffe doctrine for Luftkriegführung (conduct of air war) set air power within the overall military strategy, with critical tasks of attaining local and temporary air superiority and providing battlefield support for army and naval forces. Strategic bombing of industries and transport could be decisive longer-term options, dependent on opportunity or preparations by the army and navy. It could be used to overcome a stalemate, or used when only destruction of an opponent’s economy would be conclusive. The list excluded the idea of bombing civilians in order to destroy homes or to undermine morale, as that was considered a waste of strategic effort, but the doctrine allowed revenge attacks if German civilians were bombed. A revised edition was issued in 1940, and the continuing central principle of Luftwaffe doctrine was that destruction of an opponent’s armed forces was of primary importance.

The RAF responded to Luftwaffe developments with its 1934 Expansion Plan A rearmament scheme, and in 1936 the service was restructured into Bomber Command, Coastal Command, Training Command and Fighter Command. The last was under the command of Dowding, who opposed the doctrine that bombers were unstoppable: the invention of radar at that time could allow early detection, and prototype monoplane fighters were significantly faster than contemporary bombers. Priorities were disputed, but in December 1937, the Minister for Defence Coordination, Sir Thomas Inskip, sided with Dowding in stating that 'The role of our air force is not an early knock-out blow' but rather was 'to prevent the Germans from knocking us out', and therefore that fighter squadrons were just as necessary as bomber squadrons.

The Spanish Civil War (1936/39) gave the Luftwaffe’s expeditionary Condor Legion the opportunity to test air fighting tactics with Germany’s latest warplanes. Oberst Wolfram Freiherr von Richthofen became an exponent of air power providing ground support to other services. The difficulty of accurately hitting targets prompted Ernst Udet, the chief of the T-Amt (technical office, i.e. development wing, of the Reich ministry of aviation), to require that all new bombers had to be dive-bombers, and led to the development of the Knickebein system for nocturnal navigation. Priority was given to the manufacture of large numbers of smaller aeroplanes, and plans for a long-ranged, four-engined strategic bomber were cancelled after the death of Wever, their chief protagonist.

The early stages of World War II were characterised by successful German invasions of Norway, Denmark, the Low Countries and France, aided decisively by the Luftwaffe’s air power, which was able to establish tactical air superiority with great effectiveness. The speed with which German forces defeated most of the defending armies in Norway in early 1940 created a significant political crisis in the UK. Early in May 1940, the parliamentary debate on Norway questioned the fitness for office of Neville Chamberlain, the British prime minister. On 10 May, which was the day on which Churchill became prime minister, the Germans began 'Gelb' and thus initiated the the invasion of the Low Counties and the 'Battle of France'. At this time, RAF Fighter Command was acutely short of trained pilots and aircraft, but despite this fact Churchill ordered the despatch of more fighter squadrons to the the Air Component of the British Expeditionary Force, to support operations in France, in which the RAF suffered heavy losses. This was despite the objections of Dowding that the diversion of his forces would leave home defences farther below strength.

After the evacuation of British and French soldiers from Dunkirk and the French surrender on 22 June 1940, Hitler focused his energies primarily on the possibility of an invasion of the USSR. He believed that the British, defeated on the continent and without European allies, would quickly come to terms. The Germans were so convinced of an imminent armistice that they began constructing street decorations for the homecoming parades of victorious troops. Although the British foreign secretary, Lord Halifax, and certain elements of the British public favoured a negotiated peace with an ascendant Germany, Churchill and a majority of his cabinet refused to consider an armistice. Instead, Churchill used his skilful rhetoric to harden public opinion against capitulation and prepare the British for a long war.

From the outset of his rise to power, Hitler had expressed admiration for the UK, and throughout the 'Battle of Britain' period sought neutrality or a peace treaty with the UK. In a secret conference on 23 May 1939, Hitler had set out his rather contradictory strategy that an attack on Poland was essential and 'will only be successful if the Western Powers keep out of it. If this is impossible, then it will be better to attack in the West and to settle Poland at the same time' with a surprise attack. 'If Holland and Belgium are successfully occupied and held, and if France is also defeated, the fundamental conditions for a successful war against England will have been secured. England can then be blockaded from Western France at close quarters by the Air Force, while the Navy with its submarines extend the range of the blockade.'

When war broke out, Hitler and the Oberkommando der Wehrmacht issued a series of directives ordering, planning and stating strategic objectives. 'Directive No. 1 for the Conduct of the War', dated 31 August 1939, ordered the invasion of Poland on 1 September as planned. Potentially, Luftwaffe 'operations against England' were to 'dislocate English imports, the armaments industry, and the transport of troops to France. Any favourable opportunity of an effective attack on concentrated units of the English Navy, particularly on battleships or aircraft carriers, will be exploited. The decision regarding attacks on London is reserved to me. Attacks on the English homeland are to be prepared, bearing in mind that inconclusive results with insufficient forces are to be avoided in all circumstances.' France and the UK each declared war on Germany. On 9 October, Hitler’s Führerweisung Nr 6 planned the offensive to defeat these allies and 'win as much territory as possible in the Netherlands, Belgium, and northern France to serve as a base for the successful prosecution of the air and sea war against England'. On 29 November, the Oberkommando der Wehrmacht’s 'Directive No. 9 – Instructions For Warfare Against The Economy Of The Enemy' stated that once this coastline had been secured, the Luftwaffe and the Kriegsmarine were together to blockade British ports with sea mines. They were to attack shipping and warships and make air attacks on shore installations and industrial production. This directive remained in force in the first phase of the 'Battle of Britain', and was reinforced on 24 May during the 'Battle of France' by 'Directive No. 13', which authorised the Luftwaffe 'to attack the English homeland in the fullest manner, as soon as sufficient forces are available. This attack will be opened by an annihilating reprisal for English attacks on the Ruhr Basin.

By the end of June 1940, Germany had defeated Britain’s allies on the continent, and on 30 June the head of the Oberkommando der Wehrmacht, Generalleutnant Alfred Jodl, issued his review of options to increase pressure on the UK to agree to a negotiated peace. The first priority was to eliminate the RAF and gain air supremacy. Intensified air attacks against shipping and the economy could a longer-term effect on food supplies and civilian morale. Reprisal attacks of terror bombing had the potential to cause quicker capitulation, but the effect on morale was uncertain. On the same day, the Luftwaffe commander-in-chief, Generalfeldmarschall (from 19 July Reichsmarschall) Hermann Göring, issued his operational directive: to destroy the RAF, thus protecting German industry, and also to prevent the delivery of overseas supplies to the UK. The German supreme command argued over the practicality of these options.

In his Führerweisung Nr 16 (On Preparations for a Landing Operation against England) on 16 July, Hitler required that all be ready by the middle of August for a possible invasion he called 'Seelöwe', unless the British agreed to negotiations. The Luftwaffe reported that it would be ready to launch its major attack early in August. The Kriegsmarine commander-in-chief, Grossadmiral Erich Raeder, continued to highlight the impracticality of these plans and said that no sea invasion could take place before a time early in 1941. Hitler now argued that the UK was holding out in hope of assistance from the USSR, and the USSR was to be invaded by the middle of 1941. Göring met his air fleet commanders, and on 24 July issued instructions firstly to gain air supremacy, secondly to protect invasion forces and attack the Royal Navy’s ships, and thirdly to blockade imports and bomb harbours and supply dumps.

Issued on 1 August, Hitler’s Führerweisung Nr 17 (For the Conduct of Air and Sea Warfare against England) attempted to keep all the options open. The Luftwaffe’s 'Adlertag' campaign was to start around 5 August, subject to weather, with the aim of gaining air superiority over southern England as a necessary precondition of invasion, to give credibility to the threat and to give Hitler the option of ordering the invasion. The intention was to incapacitate the RAF so much that the UK would feel open to air attack, and would begin peace negotiations. It was also to isolate the UK and damage war production, beginning an effective blockade. Following severe Luftwaffe losses, Hitler agreed at an Oberkommando der Wehrmacht conference on 14 September that the air campaign was to intensify regardless of invasion plans. On 16 September, Göring gave the order for this change in strategy to the first independent strategic bombing campaign.

Hitler’s 1923 book Mein Kampf mostly set out his hatreds: he admired only ordinary German World War I soldiers and the UK, which he saw as an ally against communism. In 1935 Göring welcomed news that the UK, a potential ally, was rearming. In 1936 Hitler promised assistance to defend the British empire, asking only a free hand in eastern Europe, and repeated this to Halifax in 1937. That year, Joachim Ribbentrop, the German foreign minister, met Churchill with a similar proposal and when rebuffed, told Churchill that interference with German domination would mean war. To Hitler’s great annoyance, all his diplomacy failed to stop the UK from declaring war when he invaded Poland. During the fall of France, he repeatedly discussed peace efforts with his generals.

When Churchill became prime minister, there was still wide support for Halifax, who as foreign secretary openly argued for peace negotiations in the tradition of British diplomacy designed to secure British independence without war. On 20 May, Halifax secretly requested a Swedish businessman to make contact with Göring to open negotiations. Shortly after this, in the May 1940 war cabinet crisis, Halifax argued for negotiations involving the Italians, but this was rejected by Churchill with majority support. An approach made through the Swedish ambassador on 22 June was reported to Hitler, making peace negotiations seem feasible. Throughout July, as the battle started, the Germans made wider attempts to find a diplomatic solution. On 2 July, the day the armed forces were asked to start preliminary planning for an invasion, Hitler instructed Ribbentrop to draft a speech offering peace negotiations. On 19 July, Hitler made this speech to the German parliament in Berlin, appealing to 'reason and common sense', and said he could 'see no reason why this war should go on'. Hitler’s sombre conclusion was received in silence, but he did not suggest negotiations and this was perceived as being effectively an ultimatum by the British government, which rejected the offer. Halifax kept trying to arrange peace until he was sent to Washington in December as ambassador, and in January 1941 Hitler expressed continued interest in negotiating peace with the UK.

A May 1939 planning exercise by Luftflotte III found that the Luftwaffe lacked the means to do much damage to the British war economy beyond the of laying naval mines. Oberstleutnant Joseph Schmid, in charge of Luftwaffe intelligence, presented a report on 22 November 1939 stating that, 'of all Germany’s possible enemies, Britain is the most dangerous'. This 'Proposal for the Conduct of Air Warfare' argued for a counter to the British blockade and said that the 'key is to paralyse the British trade'. Instead of the German forces attacking the French, the Luftwaffe with naval assistance was to block imports to the UK and attack seaports. 'Should the [British] resort to terror measures – for example, to attack our towns in western Germany', the Germans could retaliate by bombing industrial centres and London. Parts of this appeared on 29 November 1939 in the Führerweisung Nr 9 as future actions once the coast had been seized. On 24 May 1940 Führerweisung Nr 13 authorised attacks on blockade targets, as well as retaliation for RAF bombing of industrial targets in the Ruhr industrial region.

After the defeat of France, the Oberkommando der Wehrmacht felt that Germany had won the war, and that some more pressure would persuade the UK to yield. On 30 June, Jodl issued his paper setting out options: the first was to increase attacks on shipping, economic targets and the RAF on the grounds that air attacks and food shortages were expected to break morale and lead to capitulation. Destruction of the RAF was the first priority, and invasion would be a last resort. Göring’s operational directive issued on this same day ordered the destruction of the RAF to clear the way for attacks cutting off seaborne supplies to the UK, but made no mention of invasion.

In November 1939, the Oberkommando der Wehrmacht reviewed the potential for an air- and sea-borne invasion of the UK: the Kriegsmarine was faced with the threat the Royal Navy’s larger Home Fleet posed to a crossing of the English Channel, and together with the German army viewed control of the air as a necessary precondition. The Kriegsmarine thought that air superiority alone was insufficient; the German naval staff had in 1939 produced a study on the possibility of an invasion of the UK and concluded that it also required naval superiority. The Luftwaffe said invasion could only be 'the final act in an already victorious war'.

Hitler first discussed the idea of an invasion on 21 May 1940 in a meeting with Raeder, who emphasised the difficulties and his own preference for a blockade. Jodl’s 30 June report described invasion as a last resort once the British economy had been damaged and the Luftwaffe had full air superiority. On 2 July, the Oberkommando der Wehrmacht requested the development of preliminary plans.

In the UK, Churchill described 'the great invasion scare' as 'serving a very useful purpose' by 'keeping every man and woman tuned to a high pitch of readiness.'

On 11 July, Hitler agreed with Raeder that invasion would be a last resort, and the Luftwaffe advised that gaining air superiority would take 14 to 28 days. Hitler met his army chiefs, von Brauchitsch and Halder, at the Berchtesgaden on 13 July where they presented detailed plans on the assumption that the navy would provide safe transport. Generaloberst Walther von Brauchitsch and General Franz Halder, the army commander-in-chief and the chief-of-staff of the Oberkommando des Heeres respectively, were surprised that Hitler took no interest in the invasion plans, but on 16 July Hitler issued his Führerweisung Nr 16 ordering preparations for 'Seelöwe'.

The Kriegsmarine insisted on a narrow beach-head and an extended period for landing troops; the army rejected these plans: and the Luftwaffe could begin an air attack in August. Hitler held a meeting of his army and navy commanders on 31 July. The Kriegsmarine said 22 September was the earliest possible date and proposed postponement until the following year, but Hitler preferred September. He then told von Brauchitsch and Halder that he would decide on the landing operation eight to 14 days after the air attack began. On 1 August, he issued Führerweisung Nr 17 for intensified air and sea warfare, to begin with 'Adlertag' on or after 5 August, subject to weather, keeping options open for negotiated peace or blockade and siege.

Under the continuing influence of the 1935 'Conduct of the Air War' doctrine, the main focus of the Luftwaffe command, including Göring, was in the concentration of German attacks to destroy opposing armed forces on the battlefield, and 'Blitzkrieg' close air support of the army succeeded brilliantly. The Luftwaffe’s high command echelons reserved strategic bombing for a stalemate situation or for revenge attacks, but doubted if this could be decisive on its own and regarded bombing civilians to destroy homes or to undermine morale as a waste of strategic effort.

The defeat of France in June 1940 introduced the prospect for the first time of independent air action against the UK. A July paper by the I Fliegerkorps asserted that Germany was by definition an air power: 'Its chief weapon against England is the air force, then the navy, followed by the landing forces and the army.' In 1940, the Luftwaffe would undertake a 'strategic offensive…on its own and independent of the other services', according to an April 1944 German account of their military mission. Göring was convinced that strategic bombing could win objectives that were beyond the army and navy, and gain political advantages in the Third Reich for the Luftwaffe and himself. He expected air warfare to force the UK into negotiations, as all in the Oberkommando der Wehrmacht hoped, and the Luftwaffe took little interest in planning to support an invasion.

From July 1940, the Luftwaffe faced an opponent more capable than any it had previously met: a sizeable, highly co-ordinated, well-supplied and modern air force.

So far as fighters were concerned, the Luftwaffe’s Messerschmitt Bf 109E single-engined and Bf 110C twin-engined machines fought against the RAF’s Hawker Hurricane Mk I and less numerous Supermarine Spitfire Mk I single-engined machines: the Hurricane outnumbered the Spitfire in RAF Fighter Command service by about 2/1 when the war broke out. The Bf 109E had a better climb rate and, depending on altitude, was up to 40 mph (65 km/h) faster in level flight than the Hurricane Mk I equipped with a Rotol constant-speed propeller; the speed and climb disparity with the original non-Rotol Hurricane was still greater. By the middle of 1940, all RAF Spitfire and Hurricane fighter squadrons had converted to 100-octane aviation fuel, which allowed their Rolls-Royce Merlin engines to generate significantly more power and a speed increase of some 30 mph (48 km/h) at lower altitudes through the use of an emergency boost override. In September 1940, the more powerful Hurricane Mk IIa Series 1 began to enter service in small numbers: this was capable of a maximum speed of 342 mph (550 km/h), some 20 mph (32 km/h) more than the original non-Rotol Hurricane Mk I, although it was still 15 to 20 mph (24 to 32 km/h) slower than the Bf 109E depending on altitude.

The performance of the Spitfire Mk I over the 'Dynamo' evacuation from Dunkirk in June 1940 came as a surprise to the Jagdwaffe, although the German pilots retained a strong belief that the Bf 109E was the superior fighter. Like the Hurricane, the Spitfire was armed with eight 0.303-in (7.7-mm) Browning machine guns, while most Bf 109E fighters had two 20-mm cannon supplemented by two 7.92-mm (0.312-in) machine guns. Though slow-firing, the German cannon was much more effective than the British machine gun: during the 'Battle of Britain' it was not unknown for damaged German bombers to limp home with up to 200 machine gun hits. At some altitudes, the Bf 109E could outclimb the Spitfire Mk I, and it cold also engage in negative-g manoeuvres without the engine cutting out because its Daimler-Benz DB 601 engine used an injection rather than carburetted fuel system: this allowed the Bf 109E 109 to dive away from attackers more readily as the Merlin cut out when the Spitfire’s nose was pushed down sharply. On the other hand, the Bf 109E had a much larger turning circle than its two opponents.

The Bf 109E was also used as a Jabo (Jagdbomber or fighter-bomber): the Bf 109 E-4/B and Bf 109E-7 models could carry a 250-kg (551-lb) bomb under the fuselage: the later model arrived in service during the battle. Unlike the Junkers Ju 87 Stuka dive-bomber, the Bf 109E fighter-bombers could fight on equal terms with RAF fighters after releasing their ordnance.

At the start of the battle, the Bf 110 long-range Zerstörer (destroyer) was also expected to engage in air-to-air combat while escorting the Luftwaffe bomber fleet. Although the Bf 110 was faster than the Hurricane and almost as fast as the Spitfire, its lack of manoeuvrability and acceleration meant that it was a failure in the long-range escort fighter role. On 13 and 15 August, 13 and 30 of these aircraft were lost, the equivalent of an entire Gruppe, and the type’s worst losses during the campaign. This trend continued with another eight and 15 losses on 16 and 17 August.

The most successful role of the Bf 110 performed during the battle was as a Schnellbomber (fast bomber). The Bf 110 usually employed a shallow dive to bomb the target and escape at high speed. One unit, Erprobungsgruppe 210, initially formed as the service test unit (Erprobungskommando) for the Messerschmitt Me 210 emerging successor to the Bf 110, proved that the Bf 110 could still be used to good effect in attacking small or pinpoint targets.

The RAF’s Boulton Paul Defiant single-engined turret fighter had some initial success over Dunkirk because of its resemblance to the Hurricane: Luftwaffe fighters attacking from the rear were surprised by its unusual configuration with a gun turret armed with four 0.303-in (7.7-mm) machine guns. During the Battle of Britain, however, the Defiant proved to be hopelessly outclassed. The Defiant lacked any forward-firing armament, and the heavy turret and second crewman meant it could not outrun or outmanoeuvre either the Bf 109 or the Bf 110. By the end of August, after disastrous losses, the type was withdrawn from daylight service.

The Luftwaffe’s primary bombers were the Heinkel He 111, Dornier Do 17 and Junkers Ju 88, all of them twin-engined types for level bombing at medium to high altitudes, and the Ju 87 single-engined for low-level dive-bombing. The He 111 was used in greater numbers than the others during the conflict, and was better known, partly as a result of its distinctive wing shape. The level bombers were generally accompanies in the battle by small numbers of reconnaissance versions.

Although it had been successful in previous Luftwaffe operations, the Ju 87 suffered very heavy losses in the 'Battle of Britain', particularly on 18 August, as a result of its slow speed and vulnerability to fighter interception during and immediately after dive-bombing a target. As its losses went up, along with its limited payload and range, the Ju 87 was largely removed from operations over England and diverted to the anti-shipping role before being almost wholly redeployed to the Eastern Front in 1941. For some raids, however, they were recalled: once such episode was on 13 September to attack Tangmere airfield.

The other three bomber types differed in their capabilities. The Do 17 was the slowest of the trio and had the smallest bomb load; the Ju 88 was the fastest once its mainly external bomb load had been dropped; and the He 111 had the largest internal bomb load. All three bomber types suffered heavy losses from the home-based British fighters, but the Ju 88 had significantly lower loss rates as a result of its greater speed and its ability to dive out of trouble: it had originally been designed as a dual-role level and dive bomber. Whatever their merits and demerits, all three of these German bombers required constant protection by fighters. German escort fighters were not sufficiently numerous, however, and the Bf 109E fighters were ordered to support more than 300 to 400 bombers on any given day. Later in the battler, after night bombing had become more frequent, all three were used, though as a result of its smaller bomb load, the Do 17 was used less than the He 111 and Ju 88 for this purpose.

On the British side, three bomber types were mostly used on night operations against targets such as factories, invasion ports and railway centres: these were the Armstrong-Whitworth Whitley, the Handley-Page Hampden and the Vickers Wellington. All three were twin-engined machines, and were classified by the RAF as heavy bombers, although the Hampden was a medium bomber comparable to the He 111. The twin-engined Bristol Blenheim and the obsolescent single-engined Fairey Battle were both light bombers: the Blenheim was the most numerous of the aircraft equipping RAF Bomber Command and was used in attacks against shipping, ports, airfields and factories on the continent by both day and night. The Battle squadrons, which had suffered massively heavy losses in daylight attacks during the 'Battle of France', were brought up to strength with reserve aircraft and continued to operate at night in attacks against the invasion ports, until the Battle was withdrawn from UK front-line service in October 1940.

Before the war, the RAF’s processes for selecting potential pilot candidates were opened to men of all social classes through the creation in 1936 of the RAF Volunteer Reserve, which '…was designed to appeal to…young men…without any class distinctions'. The older squadrons of the Royal Auxiliary Air Force did retain some of their upper-class exclusiveness, but their numbers were soon overtaken by the newcomers of the RAFVR: by 1 September 1939, 6,646 pilots had been trained through the RAFVR.

By the middle of 1940, the RAF had some 9,000 pilots to man about 5,000 aircraft, most of which were bombers. RAF Fighter Command was never short of pilots, but the problem of finding sufficient numbers of fully trained fighter pilots had become acute by the middle of August 1940. Aircraft production was running at 300 aircraft per week, but only 200 pilots were trained in the same period. In addition, more pilots were allocated to squadrons than there were aircraft, as this allowed squadrons to maintain operational strength despite casualties and still provide for pilot rest and leave. Another factor was that only about 30% of the 9,000 pilots were assigned to operational squadrons: 20% of pilots were involved in conducting pilot training, and another 20% were undergoing further instruction such as that offered in Canada and Southern Rhodesia to commonwealth trainees, although already qualified. The rest of the RAF’s pilot pool was assigned to staff positions as RAF policy dictated that only pilots could make many staff and operational command decisions, even in engineering matters. At the height of the fighting, and despite Churchill’s insistence, only 30 pilots were released to the front line from administrative duties.

For these reasons, and the permanent loss of 435 pilots during the 'Battle of France', together with many more wounded, and others lost in the earlier Norwegian campaign, the RAF had fewer experienced pilots at the start. It was the lack of trained pilots in the fighting squadrons, rather than the lack of aircraft, that became the greatest concern Dowding. Drawing from regular RAF forces, the Auxiliary Air Force and the Volunteer Reserve, the British were able to muster some 1,103 fighter pilots on 1 July. Replacement pilots, with little flight training and often no gunnery training, suffered high casualty rates, thus exacerbating the problem.

The Luftwaffe, on the other hand, was able to muster a larger number of more experienced fighter pilots. Drawing from a cadre of Spanish Civil War veterans, these 1,450 pilots already had already benefited from comprehensive courses as well as practical experience in aerial gunnery and the tactics best suited for fighter-versus-fighter combat. Training manuals discouraged heroism, stressing the importance of attacking only when the odds were in the pilot’s favour. Despite their generally high levels of experience, German fighter formations did not provide a sufficient reserve of pilots to allow for losses and leave, and the Luftwaffe was unable to produce enough pilots to prevent a decline in operational strength as the battle progressed.

About one-fifth of the RAF pilots who took part in the battle were from non-British countries: the RAF roll of honour for the 'Battle of Britain' recognises 595 non-British pilots, out of 2,936, as flying at least one authorised operational sortie with an eligible unit of the RAF or Fleet Air Arm between 10 July and 31 October 1940. This total included 145 Poles, 127 New Zealanders, 112 Canadians, 88 Czechoslovaks, 10 Irish, 32 Australians, 28 Belgians, 25 South Africans, 13 French, nine Americans, three Southern Rhodesians and single men from Jamaica, Barbados and Newfoundland. Altogether, in the fighter battles, the bombing raids, and the various patrols flown between 10 July and 31 October by the RAF, 1,495 aircrew were killed, of whom 449 were fighter pilots, 718 from Bomber Command, and 280 from Coastal Command. Among those killed were 47 airmen from Canada, 24 from Australia, 17 from South Africa, 30 from Poland, 20 from Czechoslovakia and six from Belgium. Some 47 New Zealanders lost their lives, these including 15 fighter pilots, 24 bomber and eight coastal aircrew.

These pilots, many of whom had fled their home countries because of German invasions, fought with distinction. No. 303 Squadron, with Polish pilots, was possibly the highest scoring of the Hurricane squadrons, for example.

An element of Italy’s Regia Aeronautica, the Corpo Aereo Italiano (Italian air corps) first saw action in the 'Battle of Britain' late in October 1940. This formation took part only in the latter stages of the battle and achieved only very limited success before it was redeployed early in 1941.

The indecision of the Oberkommando der Luftwaffe about what to do was reflected in shifts in Luftwaffe strategy. The doctrine of concentrated close air support of the army at the battlefront succeeded against Poland, Denmark and Norway, the Low Countries and France, but nonetheless incurred significant losses. The Luftwaffe had to build or repair bases in the conquered territories, and rebuild its strength. In June 1940 it began regular armed reconnaissance flights and sporadic Störangriffe (nuisance raids) by one or a few bombers by day and night. These gave crews practice in navigation and the avoidance of air defences, and set off air raid alarms which disturbed British civilian morale. Similar nuisance raids continued throughout the battle, to a time late in 1940. Scattered naval minelaying sorties began at the outset of the 'Battle of Britain', and increased gradually during the battle.

Göring’s operational directive of 30 June ordered the destruction of the RAF, including its supporting aircraft industry, to end RAF bombing raids on Germany and to facilitate attacks on ports and storage in the Luftwaffe blockade of Britain. Kanalkampf attacks on shipping in the English Channel began on 4 July, and were formalised on 11 July in an order by General Hans Jeschonnek, the Luftwaffe’s chief-of-staff, which added the arms industry as a target. On 16 July, Führerweisung Nr 16 ordered preparations for 'Seelöwe', and on the following day the Luftwaffe was ordered to stand by in full readiness. Göring met his air fleet commanders and on 24 July issued orders for gaining air supremacy, protecting the army and navy if the invasion went ahead and attacking Royal Navy ships, and continuing the blockade. Once the RAF had been defeated, Luftwaffe bombers were to move the focus of their attentions beyond London without the need for fighter escort, destroying military and economic targets.

At a meeting on 1 August the command reviewed plans produced by each Fliegerkorps with differing proposals for targets including whether to bomb airfields, but failed to decide a priority. Intelligence reports gave Göring the impression that the RAF was almost defeated, and that raids would attract British fighters for the Luftwaffe to shoot down. On 6 August he finalised plans for 'Adlertag' with Generalfeldmarschall Albert Kesselring, Generalfeldmarschall Hugo Sperrle and Generaloberst Jürgen Stumpff, the commanders-in-chief of Luftflotte II, Luftflotte III and Luftflotte V respectively: the destruction of RAF Fighter Command in the south of England was to take four days, with lightly escorted small bomber raids leaving the main fighter force free to attack RAF fighters. Bombing of military and economic targets was then to be expanded systematically northward into the Midlands until daylight attacks could proceed unhindered over the whole of the UK.

Bombing of London was to be held back while these night-time 'destroyer' attacks proceeded over other urban areas, then, in the culmination of the campaign, a major attack on the British capital was intended to cause a crisis, with refugees fleeing London just as 'Seelöwe' was scheduled to begin. With hopes for the possibility of any invasion fading, on 4 September Hitler authorised a main focus on day and night attacks on tactical targets, with London as the primary target of what became known as the 'Blitz'. With increasing difficulty in defending bombers in day raids, the Luftwaffe shifted to a strategic bombing campaign of night raids aiming to overcome British resistance by damaging infrastructure and food stocks, though intentional terror bombing of civilians was not sanctioned.

After the 'Battle of France', the Luftwaffe was regrouped into three Luftflotten (air fleets) opposite the UK’s southern and eastern coasts. Based in north-western France, Kesselring’s Luftflotte II was responsible for the bombing of south-eastern England and the London area. Based in north-western France and the Low Countries, Sperrle’s Luftflotte III concentrated its efforts on the West Country, Wales, the Midlands and north-western England. Based in Norway, Stumpff’s Luftflotte V attacked the north of England and Scotland. As the battle progressed, command responsibility shifted, with Luftflotte III taking more responsibility for the night bombing and the main weight of daylight operations falling to Luftflotte II.

The Luftwaffe initially estimated that it would take four days to defeat RAF Fighter Command over southern England, and that there would then follow a four-week offensive during which the bombers and long-range fighters would destroy all military installations throughout the country and wreck the British aircraft industry. It was planned that the campaign would start with attacks on airfields near the coast, gradually moving inland to the ring of sector airfields defending London. Later reassessments gave the Luftwaffe five weeks, from 8 August to 15 September, to establish temporary air superiority over England. RAF Fighter Command had to be destroyed, either on the ground or in the air, yet the Luftwaffe had to preserve its strength for support of the invasion. Thus the Luftwaffe had to maintain a high kill/loss kill ratio over the RAF’s fighter forces. The only alternative to the goal of air superiority was a terror bombing campaign aimed at the civilian population, but this was considered a last resort and was forbidden by Hitler. The Luftwaffe adhered in broad terms to this scheme, but its commanders had differed in opinion on strategy. Sperrle wished to eradicate the air-defence infrastructure by bombing it. Kesselring championed direct attacks on attacking London directly with the object either of bombing the British government into submission or of drawing RAF fighters into a decisive battle. Göring did nothing to resolve this disagreement between his two senior commanders on the European mainland and gave only vague directives during the initial stages of the battle: in fact, Göring seemed incapable of deciding which strategy to pursue.

In tactical terms, the Luftwaffe employed a loose section of two aircraft, the Rotte (pack), based on a leader (Rottenführer) followed at a distance of about 220 yards (200 m) by his wingman (Rottenhund or Katschmarek, the turning radius of the Bf 109 enabling both aircraft to turn together at high speed. The Katschmarek flew slightly higher and was trained always to stay with his leader. With more room between them, both fighters could spend less time maintaining formation and more time looking around and covering each other’s blind spots. Attacking aircraft could be sandwiched between the two Bf 109 fighters.

The Rotte concept was developed from basic principles established in World War I by the 'ace' Hauptmann Oswald Boelcke in 1916. In 1934 the Finnish air arm adopted a similar concept, called the partio (patrol) of two aircraft and the parvi (two patrols) of four aircraft, for similar reasons, though Luftwaffe pilots during the Spanish Civil War (led by Günther Lützow and Werner Mölders, among others) are generally given credit. The Rotte allowed the Rottenführer to concentrate on shooting down aircraft as the Katschmarek provided protection, but this meant that few wingmen had the chance to score victories, which led to a measure of resentment in the lower ranks, in which it was felt that the high scores came at their expense.

Two Rotten combined as a Schwarm, in which all the pilots could watch what was happening around them. Each Schwarm in a Staffel (squadron) flew at staggered heights and with about 220 yards (200 m) between them, making the formation difficult to spot at longer ranges and allowing for a great deal of tactical flexibility. By using a tight cross-over turn, a Schwarm could change direction quickly.

The Bf 110 used the same Schwarm formation as the Bf 109 but was seldom able to use this to the same advantage. The Bf 110’s most successful method of attack was the 'bounce' from above. When attacked, Zerstörergruppen (Bf 110 wings) increasingly resorted to forming large defensive circles in which each Bf 110 guarded the tail of the aeroplane ahead of it. Göring ordered that these circular formations be renamed 'offensive circles' in a vain bid to effect an improvement in the Bf 110 crews' rapidly declining morale. These conspicuous formations were often successful in attracting RAF fighters that were sometimes 'bounced' by higher-flying Bf 109 fighters, and this led to the oft-repeated misconception that the Bf 110 was escorted by the Bf 109.

Higher-level Luftwaffe tactics were influenced by the fighter tactics. The Bf 110 proved too vulnerable against the nimbler single-engined RAF fighters and the bulk of fighter escort duties devolved to the Bf 109. Fighter tactics were then complicated by bomber crews, who demanded closer protection. After the hard-fought battles of 15 and 18 August, Göring met unit leaders. The need for the fighters to rendezvous with the bombers at the agreed time was stressed. It was also decided that one bomber Gruppe (wing) could only be protected effectively by several Bf 109 Gruppen. Göring stipulated that as many fighters as possible were to be left free for freie Jagd ('free hunt' roving fighter sweeps which preceded a raid to try to sweep defenders out of the raid’s path). The Ju 87 units, which had suffered heavy casualties, were only to be used under favourable circumstances. Early in September, as a result of increasing complaints by bomber crews about the apparent ability of RAF fighters to get through the escort screen, Göring ordered an increase in close escort duties. This was a decision which shackled many of the Bf 109 fighters to the bombers, at speed with were not fuel-economical, and although the fighters were then more successful at protecting the bombers, their casualties mounted, primarily because they were forced to fly and manoeuvre at reduced speeds.

The Luftwaffe varied its tactics in its efforts to break RAF Fighter Command. It launched many freie Jagd sweeps to draw up RAF fighters, but RAF fighter controllers were often able to detect these and position squadrons to avoid them, keeping to Dowding’s plan to preserve fighter strength for the bomber formations. The Luftwaffe also tried using small formations of bombers as bait, covering them with large numbers of escorts, and while this was more successful, escort duty kept the fighters tied to the slower bombers and rendered them more vulnerable.

By September, the standard tactics for German raids had become a combination of techniques. A freie Jagd preceded the main attack formations. The bombers flew at altitudes between 16,405 and 19,685 ft (5000 and 6000 m), escorted closely by fighters. Escorts were divided into two parts (usually Gruppen), some operating close to the bombers and others a few hundred yards away and a little above their charges. If the formation was attacked from starboard, the starboard section engaged the attackers, the top section moving to starboard and the port section to the top position; if the attack came from port, the system was reversed. British fighters coming from the rear were engaged by the rear section and the two outside sections similarly moving to the rear. If the threat came from above, the top section went into action while the beam sections gained height to be able to follow RAF fighters down as they broke away. If attacked, all sections flew in defensive circles. These tactics were skilfully evolved and carried out and were difficult to counter.

The most significant disadvantage faced by Bf 109 pilots was that without long-range drop tanks, which were introduced in limited numbers in the late stages of the battle, usually of 66-Imp gal (300-litre) capacity, the Bf 109 had an endurance of just over one hour and, in the case of the Bf 109E, a range of 373 miles (600 km). Once over England, a Bf 109 pilot had to keep an eye on the red 'low fuel' light on his fighter’s instrument panel: once this was illuminated, he was forced to turn back and head for France. With the prospect of two long flights over water and knowing their range was substantially reduced when escorting bombers or during combat, the Jagdflieger coined the term Kanalkrankheit (Channel sickness).

The Luftwaffe was also adversely affected by its lack of military intelligence about the British defences. The German intelligence services were multiply fractured and plagued by rivalry, and their performance has been described as 'amateurish'. By 1940, there were few German agents operating in the UK and a handful of bungled attempts to insert more agents into the country were foiled.

The interception of British radio transmissions allowed the German to deduce that the RAF fighters were controlled from ground facilities: in July and August 1939, for example, the airship Graf Zeppelin, which was packed with equipment for listening to RAF radio and radio direction finding (radar) transmissions, flew around the British coast. Although the Luftwaffe correctly interpreted these new ground-control procedures, they were incorrectly assessed as being rigid and ineffectual. A British radar system was well known to the Luftwaffe from intelligence gathered before the war, but the highly developed 'Dowding system' linked with fighter control had been a well-kept secret. Even when good information existed, such as a November 1939 Abwehr assessment of RAF Fighter Command strengths and capabilities by Abteilung V, it was ignored if it did not match conventional preconceptions. On 16 July 1940, Abteilung V, commanded by Schmid, produced a report on the RAF and on the UK’s defensive capabilities which was adopted by front-line commanders as a basis for their operational plans. One of the most conspicuous failures of the report was the lack of information on the RAF’s radar network and control systems capabilities: it was assumed that the system was rigid and inflexible, with the RAF fighters electronically 'tied' to their home bases. An optimistic and, as it later emerged, erroneous conclusion reached was: 'Supply Situation… At present the British aircraft industry produces about 180 to 300 first-line fighters and 140 first-line bombers a month. In view of the present conditions relating to production (the appearance of raw material difficulties, the disruption or breakdown of production at factories owing to air attacks, the increased vulnerability to air attack owing to the fundamental reorganisation of the aircraft industry now in progress), it is believed that for the time being output will decrease rather than increase. In the event of an intensification of air warfare it is expected that the present strength of the RAF will fall, and this decline will be aggravated by the continued decrease in production.'

As a result of this statement, reinforced by another more detailed report, issued on 10 August, there developed in the minds of the Luftwaffe that the RAF would run out of front-line fighters. The Luftwaffe believed it was weakening RAF Fighter Command at three times the actual attrition rate, and on many occasions the German leadership believed that RAF Fighter Command’s strength had collapsed, only to discover that the latter was able to send up defensive formations at will.

Throughout the 'Battle of Britain', the Luftwaffe had to make use of numerous reconnaissance sorties to offset poor intelligence. Reconnaissance aircraft, for the most part Do 17 machines but later Bf 110 aircraft, proved easy prey for British fighters, as it was seldom possible for them to be escorted by Bf 109 fighters. Thus, the Luftwaffe operated 'blind' for much of the battle, unsure of its opponent’s true strengths, capabilities and deployments. Many of the RAF Fighter Command airfields were never attacked, while raids against supposed fighter airfields fell instead on bomber or coastal defence stations. The results of bombing and air fighting were consistently exaggerated as a result of inaccurate claims, over-enthusiastic reports and the difficulty of confirmation over British territory. In the euphoric atmosphere of perceived victory, the Luftwaffe leadership became increasingly disconnected from reality. This lack of leadership and solid intelligence meant that the Germans did not adopt a consistent strategy, even when the RAF had its back to the wall. Moreover, there was never a systematic focus on one type of target (such as air bases, radar stations and aircraft factories), and asa result the already haphazard attack effort was further diluted.

While the British were using radar for air defence more effectively than the Germans realised, the Luftwaffe attempted to press its own offensive through the use of advanced radio navigation systems of which the British were initially unaware. One of these was Knickebein (bent leg), which was employed at night and for raids where precision was required. It was rarely used during the 'Battle of Britain'.

The Luftwaffe was much better prepared than the RAF for the task of air/sea rescue, specifically tasking the Seenotdienst unit, equipped with about 30 Heinkel He 59 twin-engined biplane floatplanes, with recovering downed aircrew from the North Sea, the English Channel and the Dover Straits. In addition, Luftwaffe aircraft were equipped with life rafts, and the aircrew were provided with sachets of a chemical called fluorescein which, on reacting with water, created a large, easy-to-see, bright green patch. In accordance with the Geneva Convention, the He 59 floatplanes were unarmed and painted white with civilian registration markings and red crosses. Nevertheless, RAF aircraft attacked these aircraft, as some were escorted by Bf 109 fighters.

After single He 59 floatplanes had been forced to land on the sea by RAF fighters on 1 and 9 July, on 13 July a controversial order was issued to the RAF which stated that from 20 July Seenotdienst aircraft were to be shot down. One of the reasons given by Churchill was that 'We did not recognise this means of rescuing [German] pilots so they could come and bomb our civil population again…all German air ambulances were forced down or shot down by our fighters on definite orders approved by the War Cabinet.'

The British also believed that the crews of air/sea rescue aircraft would report on convoys, the Air Ministry issuing a communiqué to the German government on 14 July that the UK was 'unable, however, to grant immunity to such aircraft flying over areas in which operations are in progress on land or at sea, or approaching British or Allied territory, or territory in British occupation, or British or Allied ships. Ambulance aircraft which do not comply with the above will do so at their own risk and peril.'

The white He 59 floatplanes were soon repainted in camouflage colours and armed with defensive machine guns. Although another four such aircraft were shot down by RAF aircraft, the Seenotdienst continued to recover downed Luftwaffe and Allied aircrew throughout the battle.

During early tests of the British 'Chain Home' radar system, the slow flow of information from the radars and observers to the aircraft often caused them to miss their 'bandit' targets. The solution, which became known as the 'Dowding system', was the creation of a set of reporting chains to move information from the various observation points to the pilots in their fighters. Reports from radars and the Observer Corps were sent directly to the headquarters of RAF Fighter Command at Bentley Priory, where they were 'filtered' to combine multiple reports of the same formations into single tracks. Telephone operators then forwarded only the information of interest to the group headquarters, one level down from the command level, where the map was re-created. This process was repeated to produce another version of the map at the next-down sector level, covering a much smaller area. Looking over their maps, group-level commanders selected squadrons to attack particular targets. From that point, the sector operators gave commands to the fighters to arrange a specific interception, as well as return them to base. Sector stations also controlled the anti-aircraft batteries in their area: an army officer sat beside each fighter controller and directed the gun crews when to open and cease fire.

The 'Dowding system' dramatically improved the speed and accuracy of the information that flowed to the pilots. During the period early in the war, it was expected that an average interception mission might have a 30% chance of ever seeing its target, but during the 'Battle of Britain', the 'Dowding system' maintained an average rate of more than 75%, with several examples of 100% rates in which every fighter despatched found and intercepted its target. By contrast, Luftwaffe fighters attempting to intercept raids had to randomly seek their targets and often returned home having never seen an opposing aeroplane. The result was that RAF fighters were as effective as two or more Luftwaffe fighters, greatly offsetting, or overturning, the disparity in actual numbers.

While Luftwaffe intelligence reports underestimated the strength of British fighter forces and rates of aircraft production, the British intelligence estimates went the other way: they overestimated German aircraft production, numbers and range of aircraft available, and the numbers of pilots available to the Luftwaffe. In action, the Luftwaffe believed from the claims of it pilots and the impression given by aerial reconnaissance that the RAF was close to defeat, and the British made strenuous efforts to overcome the perceived advantages held by their opponents.

It is still unclear to what extent the British intercepts of Enigma-ciphered German radio traffic, used for high-security communications, affected the battle. 'Ultra', the information obtained from the intercepts and decrypts of Enigma-ciphered traffic, gave the highest echelons of the British command a view of German intentions. According to F. W. Winterbotham, who was the senior Air Staff representative in the Secret Intelligence Service, 'Ultra' helped to establish the strength and composition of the Luftwaffe’s formations, and the aims of its commanders, and provided early warning of some raids. Early in August it was decided that a small unit would be set up at the headquarters of RAF Fighter Command to process the flow of information from Bletchley Park and provide Dowding only with the most essential material. Thus the Air Ministry did not have to send a continual flow of information to the headquarters of RAF Fighter Command, so helping to preserve secrecy, and Dowding was not inundated with non-essential information. Park, the commander of No. 11 Group, and his controllers were also told about 'Ultra'. In a further attempt to camouflage the existence of 'Ultra', Dowding created No. 421 (Reconnaissance) Flight. This unit, which later became No. 91 Squadron, was equipped with Hurricane and Spitfire aircraft which were sent out to search for and report Luftwaffe formations approaching England, thereby providing a plausible source of information. In addition, the Y Service radio-listening branch, monitoring the patterns of Luftwaffe radio traffic, contributed considerably to the early warning of raids.

Late in the 1930s, RAF Fighter Command expected to face bombers but not single-engined fighters over the UK. A series of 'Fighting Area Tactics' was formulated and rigidly imposed, these involving a series of manoeuvres designed to concentrate a squadron’s firepower to bring down bombers. RAF fighters flew in tight, V-shaped sections ('vics') of three aircraft, with four such sections in tight formation. Only the squadron leader at the front was free to watch for the opposition as the other pilots had to concentrate on keeping station. Training also emphasised by-the-book attacks by sections breaking away in sequence. RAF Fighter Command recognised the weaknesses of this concept early in the battle, but felt that it would be too risky to change tactics during the battle because replacement pilots, many of them with only minimal flying time, could not be readily retrained, and inexperienced pilots needed the firm leadership in the air which only rigid formations could provide. German pilots dubbed the RAF formations Idiotenreihen (rows of idiots) because they left squadrons vulnerable to attack.

Front-line British pilots were acutely aware of the inherent deficiencies of their own tactics. A compromise was adopted whereby squadron formations used much looser formations with one or two 'weavers' flying independently above and behind to provide increased observation and rear protection: these tended to be the least experienced men and were often the first to be shot down without the other pilots even noticing that they were under attack. During the battle, No. 74 Squadron under the command of Squadron Leader Adolph Malan adopted a variation of the German formation called the 'fours in line astern', which was a vast improvement on the old three-aircraft 'vic'. Malan’s formation later came into general use by RAF Fighter Command.

The weight of the battle fell upon No. 11 Group in south-eastern England under Park’s leadership. Park’s tactics were to dispatch individual squadrons to intercept raids. The intention was to subject incoming bombers to continual attacks by relatively small numbers of fighters and try to break up the tight German formations. Once formations had fallen apart, the stragglers could be picked off singly. Where multiple squadrons intercepted a raid, the procedure was for the slower Hurricanes to tackle the bombers while the faster and more agile Spitfires engaged the fighter escort. This ideal was not always achieved, resulting in occasions when Spitfires and Hurricanes reversed roles. Park also issued instructions to his units to engage in frontal attacks against the bombers, which were more vulnerable to such attacks. Again, in the environment of fast-moving, three-dimensional air battles, few RAF fighter units were able to attack the bombers head-on.

During the battle, some commanders, notably Air Vice Marshal T. Leigh-Mallory, commander of No. 12 Group to the north of No. 11 Group, proposed that squadrons be formed into 'big wings', each comprising at least three squadrons, to attack the Germans en masse in a tactic pioneered by Squadron Leader Douglas Bader, commander of No. 242 Squadron and later of the Duxford Wing. Proponents of this tactic claimed interceptions in large numbers caused greater German losses while reducing their own casualties. Opponents pointed out the big wings took too long to group in the air, and that the concept ran a greater risk of fighters being caught on the ground as they refuelled. The 'big wing' idea also caused pilots to overclaim their kills asa consequence of the confusion of a more intense battle zone. This led to the belief big wings were far more effective than they actually were.

The issue caused intense friction between Park and Leigh-Mallory, as the task of No. 12 Group was to protect No. 11 Group’s airfields while Park’s squadrons intercepted incoming raids. The delay in forming 'big wings' meant the formations often did not arrive at all or only after the German bombers had hit No. 11 Group’s airfields. To highlight the problem of 'big wing' capabilities, Dowding submitted a report compiled by Park to the Air Ministry on 15 November. The report highlighted the fact that between 11 September and 31 October, the extensive use of the 'big wing' had resulted in just 10 interceptions and one German aircraft destroyed, but this report was ignored. Post-war analysis confirms that the approach of Dowding and Park was best for No. 11 Group.

Dowding’s removal from his position as the head of RAF Fighter Command in November 1940 has been blamed on this struggle between the daylight strategies of Park and Leigh-Mallory. The intensive raids and destruction wrought during the 'Blitz' damaged both Dowding and Park in particular, for the failure to produce an effective night-fighter defence system, something for which the influential Leigh-Mallory had long criticised them.

Aircraft of Portal’s RAF Bomber Command and Air Marshal Sir Frederick Bowhill’s RAF Coastal Command flew offensive sorties against targets in Germany and France during the battle. An hour after the declaration of war, RAF Bomber Command had launched raids on warships and naval ports by day, and in night raids dropped leaflets as it was considered illegal to bomb targets which could result in civilian losses. After the initial disasters of the war, with Wellington twin-engined bombers shot down in large numbers attacking Wilhelmshaven and the slaughter of the Battle single-engined bomber squadrons sent to France, it became clear that they would have to operate mainly at night to avoid incurring very high losses. Churchill became prime minister on 10 May 1940, and the War Cabinet on 12 May agreed that German actions justified 'unrestricted warfare': on 14 May an attack on the night of 14/15 May was authorised against oil and rail targets in Germany. At the urging of Clement Attlee, the deputy prime minister, the cabinet on 15 May authorised a full bombing strategy against 'suitable military objectives', even where this could result in civilian casualties. That same evening, there began a night bombing campaign against the German oil industry, communications, crops and forests, mainly in the Ruhr area. The RAF lacked any accurate night navigation capability, and it aircraft carried only small bomb loads. As the threat mounted, RAF Bomber Command changed targeting priority on 3 June 1940 to attack the German aircraft industry. On 4 July, the Air Ministry gave RAF Bomber Command orders to attack ports and shipping. By September, the build-up of invasion barges in the English Channel ports had become a top-priority target.

On 7 September, the government issued a warning that the German invasion could be expected within the next few days, and that night RAF Bomber Command attacked the English Channel ports and supply dumps. On 13 September, the command carried out another large raid on the English Channel ports, sinking 80 large barges in the port of Ostend. Some 84 barges were sunk in Dunkirk after another raid on 17 September, and by 19 September almost 200 barges had been sunk. The loss of these barges may have contributed to Hitler’s decision to postpone 'Seelöwe' indefinitely. The success of these raids resulted in part from the Germans' possession of only few Freya radar stations in France, so that the air defence of the French harbours were not nearly as good as the air defences over Germany. RAF Bomber Command had directed some 60% of its strength against the English Channel ports.

The Blenheim twin-engined light bomber units also raided German-occupied airfields throughout the period between July and December 1940, both during daylight hours and at night. Although most of these raids were unproductive, there were some successes: on 1 August, for example five out of 12 Blenheim bombers sent to attack Haamstede and Evère (Brussels) were able to destroy or heavily damage three Bf 109 fighters of the II/JG27 and apparently kill a Staffelkapitän. Two other Bf 109 fighters were claimed by Blenheim gunners. Another successful raid on Haamstede was made by a single Blenheim on 7 August: this destroyed one Bf 109 of the 4./JG54, heavily damaged another and caused lighter damage to four more.

There were, however, some missions which resulted in an almost 100% casualty rate among the Blenheim bombers. One such operation was mounted on 13 August against a Luftwaffe airfield near Aalborg in north-eastern Denmark by 12 aircraft of No. 82 Squadron: one Blenheim returned early, and the other 11, which reached Denmark, were shot down, five by Flak and six by Bf 109 fighters. Of the 33 crewmen who took part in the attack, 20 were killed and 13 taken prisoner.

Blenheim-equipped units had also been formed to carry out long-range strategic reconnaissance missions over Germany and German-occupied territories. In this role, the Blenheim again proved to be too slow and vulnerable against Luftwaffe fighters, and suffered constant casualties.

RAF Coastal Command directed its attention towards the protection of British shipping, and the destruction of German shipping. As invasion became more likely, the command participated in the attacks on French harbours and airfields, laying mines and mounting numerous reconnaissance missions over the German-held coast. In all, some 9,180 sorties were flown by bombers from July to October 1940. Although this was much less than the 80,000 sorties flown by fighters, bomber crews suffered about half the total casualties borne by their fighter colleagues. The bomber contribution was, therefore, considerably more dangerous on a loss-per-sortie comparison.

Bomber, reconnaissance and anti-submarine patrol operations continued throughout these months with little respite and none of the publicity accorded to RAF Fighter Command. In his famous 20 August speech about 'The Few', praising RAF Fighter Command, Churchill also made a point of mentioning RAF Bomber Command’s contribution, adding that bombers were even then striking back at Germany: this part of the speech is often overlooked even today. The Battle of Britain Chapel in Westminster Abbey lists in a roll of honour, RAF 718 Bomber Command crew members, and 280 of RAF Coastal Command who were killed between 10 July and 31 October.

Attacks by RAF Bomber Command and RAF Coastal Command against invasion barge concentrations in English Channel ports were widely reported by British media during September and October 1940. In what became known as the 'Battle of the Barges', RAF attacks were claimed in British propaganda to have sunk large numbers of barges, and to have created widespread chaos and disruption to German invasion preparations. Given the volume of British propaganda interest in these bomber attacks during September and earlier October, it is striking how quickly this was overlooked once the 'Battle of Britain' had come to an end. Even by the middle of the war, the bomber pilots' efforts had been largely eclipsed by a continuing focus on 'the Few', this resulting from the Air Ministry’s continuing lauding of the 'fighter boys', beginning with the March 1941 Battle of Britain propaganda pamphlet.

One of the biggest oversights of the entire British system was the lack of adequate air-sea rescue organisation. The RAF had started organising such a system in 1940 with high-speed launches operating from flying boat bases and at some overseas locations, but it was still thought that the limited number of over-Channel flights meant that there was no need for a rescue service to cover these areas. Downed pilots and aircrew, it was hoped, would be picked up by any passing boats or ships, or the local life boat would be alerted, assuming that someone had seen the pilot going into the water.

RAF aircrew were issued with a life jacket, but in 1940 this still required manual inflation, which was almost impossible for someone who was injured or in shock. The waters of the English Channel and Straits of Dover are cold, even in the middle of summer, and clothing issued to RAF aircrew did little to insulate them against these freezing conditions. The RAF also imitated the German practice of issuing fluorescein. A conference in 1939 had placed air/sea rescue under the auspices of RAF Coastal Command. Because pilots had been lost at sea during the Kanalkampf, on 22 August control of RAF rescue launches was passed to the local naval authorities and 12 Westland Lysander single-engined short-range reconnaissance aircraft were allocated to RAF Fighter Command to help look for pilots at sea. In all, some 200 pilots and aircrew were lost at sea during the battle, and no proper air/sea rescue service was formed until 1941.

The 'Battle of Britain' was fought over distinct geographical areas, and there have been differing opinions on significant dates: when the Air Ministry proposed 8 August as the start, Dowding responded that operations 'merged into one another almost insensibly' and proposed 10 July as the onset of increased attacks. With the caution that phases drifted into each other and dates are not firm, it is now generally agreed that five main phases can be identified: the first of these, between
26 June and 16 July was known to the Germans as the Störangriffe (nuisance raids), which were scattered small-scale probing attacks by both day and night, armed reconnaissance, minelaying and, from 4 July, increasing daylight attacks on shipping in the English Channel; the second, from 17 July to 12 August, was the intensified Kanalkampf daylight offensive against shipping, ports and coastal airfields as well a night attacks on RAF and aircraft manufacturing facilities; the third, from 13 August to 6 September was the Adlertag main assault in the German attempt to destroy the RAF in southern England, including massive daylight attacks on RAF airfields, followed from 19 August by heavy night bombing of ports and industrial cities, including the suburbs of London; the fourth, between 7 September and 2 October was the first phase of the 'Blitz' with the main focus day and night attacks on London; and the sixth, between 3 and 31 October was the major night bombing campaign, primarily against London, with daylight attacks now confined to small scale fighter-bomber Störangriffe raids designed to lure RAF fighters into dogfights.

After Germany’s rapid territorial gains in the 'Battle of France', the Luftwaffe had reorganised its forces, established bases along the coast, and rebuilt its formations and units after their heavy losses in the earlier campaigns. It began small-scale bombing raids on the UK on the night of 5/6 June, and continued sporadic attacks throughout June and July. The first large-scale attack was undertaken at night, on 18/19 June, when small raids between Yorkshire and Kent involved some 100 bombers.These Störangriffe, which involved only a few aeroplanes or sometimes just one, were used to train bomber crews in both day and night attacks, to test defences and try out methods, with most flights at night. The Germans discovered that, rather than carrying small numbers of large high explosive bombs, it was more effective to employ larger numbers of small bombs, and that incendiaries had to drop ob a large area to set effective fires. These training flights continued throughout August and into the first week of September. On the other side of the coin, the raids also gave the British time to assess the German tactics, and invaluable time for the RAF fighters and anti-aircraft defences to prepare and gain practical experience.

The attacks were widespread: over the night of 30 June alarms were set off in 20 counties by just 20 bombers, and then on the following day the first daylight raids occurred, against both Hull in Yorkshire and Wick in Caithness. On 3 July most flights were reconnaissance sorties, but 15 civilians were killed when bombs hit Guildford in Surrey. Numerous small Störangriffe raids, both day and night, were made daily through August, September and into the winter, with objectives such as drawing RAF fighters up to battle, destruction of specific military and economic targets, and triggering air-raid warnings to affect civilian morale. Four major air raids in August involved hundreds of bombers, and in the same month 1,062 small raids were made across the whole of the UK.

The Kanalkampf took the form of a series of running fights over convoys in the English Channel. It was launched partly because Kesselring and Sperrle were not sure about what else to do, and partly because it gave German aircrews some training and a chance to probe the British defences. Dowding could provide only minimal protection for the convoys, and the fighting off the coast tended to favour the Germans, whose bomber escorts had the advantage of altitude and outnumbered the RAF fighters. From 9 July reconnaissance probing by Do 17 bombers put a severe strain on RAF pilots and machines, with high RAF losses to Bf 109 fighters. When nine Defiant turret fighters of No. 141 Squadron went into action on 19 July, six were lost to Bf 109s before a squadron of Hurricanes intervened. On 25 July a coal convoy and escorting destroyers suffered such heavy losses to attacks by Ju 87 dive-bombers that the Admiralty decided convoys should travel at night: the RAF shot down 16 raiders but itself lost seven aircraft. By 8 August 18 coal ships and four destroyers had been sunk, but the Royal Navy was determined to send a convoy of 20 ships through rather than move the coal by railway. After repeated dive-bomber attacks on that day, six ships had been badly damaged, four sunk and only four reached their destination. The RAF lost 19 fighters and shot down 31 German aircraft. The Royal Navy now cancelled all further convoys through the English Channel and sent the cargo by rail. Even so, these early combat encounters provided both sides with experience.

The main German attack on the RAF’s defences was codenamed 'Adlerangriff' (eagle attack). Intelligence reports had given Göring the impression that the RAF was on the verge of defeat, and raids would attract the last British fighters for the Luftwaffe to shoot down. Agreed on 6 August, the strategy was to destroy RAF Fighter Command across the south of England in four days, then the bombing of military and economic targets was to be extended systematically up to the Midlands until daylight attacks could proceed unhindered over the whole of the UK, culminating in a major bombing attack on London.

Poor weather delayed Adlertag (eagle day) until 13 August, and on the preceding day the first German attempt was made to blind the 'Dowding system', when aircraft from the Erprobungsgruppe 210 specialised fighter-bomber unit attacked four radar stations, of which three were briefly knocked out of service but were back working within six hours. The raids appeared to show that British radars were difficult to knock out. The failure to mount follow-up attacks allowed the RAF to get the stations back on the air, and the Luftwaffe neglected attacks on supporting infrastructure such as phone lines and power stations, which could have rendered the radars useless, even if the towers themselves, which were very difficult to destroy, remained intact.

Adlertag opened with a series of attacks, led again by Erprobungsgruppe 210, on coastal airfields used as forward landing grounds for RAF fighters, as well as satellite airfields including Manston and Hawkinge. (Satellite airfields were mostly fully equipped but did not have the sector control room which allowed Sector airfields such as Biggin Hill to monitor and control RAF fighter units. RAF units from Sector airfields often flew into a satellite airfield for operations during the day, returning to their home airfield in the evenings.) As the week drew on, the airfield attacks moved farther inland, and repeated raids were made on the radar chain. 15 August was 'The Greatest Day', when the Luftwaffe mounted the largest number of sorties of the campaign.

Luftflotte V attacked targets in north-eastern England. Believing that RAF Fighter Command’s strength was concentrated in the south, raiding forces from Denmark and Norway ran into unexpectedly strong resistance. Inadequately escorted by Bf 110 fighters as the Bf 109 machines lacked the range to escort raids from Norway), bombers were shot down in large numbers. North-eastern England was attacked by 65 He 111 bombers escorted by 34 Bf 110 fighters, and RAF Great Driffield was attacked by 50 unescorted Ju 88 bombers. Out of 115 bombers and 35 fighters despatched, 75 aircraft were destroyed and many others damaged beyond repair. Furthermore, as a result of early engagement by RAF fighters, many of the bombers dropped their payloads before reaching their designated targets. As a result of these casualties, Luftflotte V made no appearance in strength again during the campaign.

18 August, which had the greatest number of casualties to each side, has been dubbed 'The Hardest Day', after after this grinding battle, exhaustion and the weather reduced operations for most of a week, allowing the Luftwaffe to review its performance. 'The Hardest Day' had sounded the end for the Ju 87 in the campaign, for experience had revealed that this veteran Blitzkrieg weapon was too vulnerable to fighters to operate over the UK and, in order to preserve the dive-bomber force Göring withdrew it from the fighting. This removed the Luftwaffe’s primary precision-attack weapon and shifted the burden of pinpoint attacks onto Erprobungsgruppe 210, which was already stretched virtually to the limit. The Bf 110 proved too clumsy for dogfighting with single-engined fighters, and its participation was also scaled back: the Bf 110 was hereafter used only when range required its use or when sufficient single-engined escorts could not be provided for the bombers.

At this time Göring made yet another important decision: to order more bomber escorts at the expense of free-hunting sweeps. To achieve this, the weight of the attack now fell on Luftflotte II, so many of the Bf 109 units in Luftflotte III were transferred to Kesselring’s command, reinforcing the fighter bases in the Pas de Calais. Stripped of its fighters, Luftflotte III was now to concentrate on the night bombing campaign. Expressing disappointment with the fighter performance thus far in the campaign, Göring also made sweeping changes in the command structure of the fighter units, replacing many Geschwaderkommodore with younger, more aggressive pilots such as Adolf Galland and Werner Mölders.

Finally, Göring stopped the attacks on the radar chain. These were seen as unsuccessful, and neither the Göring nor his subordinates realised how vital the Chain Home stations were to the defence systems. It was known that radar provided some early warning of raids, but the belief among German fighter pilots was that anything bringing the British fighters up into combat was to be encouraged.

During the afternoon of 15 August, Hauptmann Walter Rubensdörffer, leading Erprobungsgruppe 210, mistakenly bombed Croydon airfield on the south-eastern outskirts of London, instead of the intended target, RAF Kenley.

German intelligence reports made the Luftwaffe optimistic that the RAF, thought to be dependent on local air control, was struggling with supply problems and pilot losses. After a major raid had attacked RAF Biggin Hill on 18 August, Luftwaffe aircrew said they had been unopposed, the airfield had been completely destroyed and asked whether the UK was already finished. In accordance with the strategy agreed on 6 August, defeat of the RAF was to be followed by bombing military and economic targets, systematically expanding into the Midlands.

On 19 August, Göring ordered attacks on aircraft factories, and 60 raids on the night of 19/20 August targeted the aircraft industry and harbours, and bombs fell on suburban areas around London, more specifically Croydon, Wimbledon and the Maldens. Night raids were delivered during 21/22 August on Aberdeen, Bristol and South Wales, and in the morning bombs were dropped on Harrow and Wealdstone, on the outskirts of London. Overnight on 22/23 August, the output of an aircraft factory at Filton near Bristol was drastically affected by a raid in which Ju 88 bombers dropped high explosive bombs. On the night of 23/24 August more than 200 bombers attacked the Fort Dunlop tyre factory in Birmingham, with a significant effect on production. A sustained bombing campaign began on 24 August with the largest raid so far, killing 100 persons in Portsmouth, and that night several areas of London were bombed: the East End was set ablaze and bombs landed on central London. It had been claimed that these bombs were dropped accidentally by a group of He 111 aircraft which had failed to find their target, but this claim has been contested.

More night raids were made around London on 24/25 August, when bombs fell on Croydon, Banstead, Lewisham, Uxbridge, Harrow and Hayes. London was on red alert over the night of 28/29 August, with bombs reported in Finchley, St Pancras, Wembley, Wood Green, Southgate, the Old Kent Road, Mill Hill, Ilford, Chigwell and Hendon.

Göring’s directive of 23 August ordered incessant attacks on the aircraft industry and on the RAF’s ground organisation to force the RAF to use its fighters, continuing the tactic of luring the British machines up into combat to be destroyed, and added that focused attacks were to be made on RAF airfields.

From 24 August onward, the battle was a fight between Kesselring’s Luftflotte II and Park’s No. 11 Group. The Luftwaffe concentrated its strength on knocking out RAF Fighter Command and made repeated attacks on the airfields, and of the 33 heavy attacks in the following two weeks, 24 were directed against airfields. The key Sector stations were hit repeatedly: Biggin Hill and Hornchurch four times each; and Debden and North Weald twice each. Croydon, Gravesend, Rochford, Hawkinge and Manston were also attacked in strength. RAF Coastal Command’s Eastchurch airfield was bombed at least seven times because it was believed to be an RAF Fighter Command facility. At times these raids caused some damage to the sector stations, threatening the integrity of the 'Dowding system'.

To offset some of the British losses, some 58 Fleet Air Arm fighter pilot volunteers were seconded to RAF squadrons, and a similar number of former Battle pilots was also used. Most replacements from operational training units had as little as nine hours flying time and no gunnery or air-to-air combat training. At this point, the multi-national nature of RAF Fighter Command came to the fore. Many squadrons and personnel, including high-level commanders, from the air forces of the dominions were already attached to the RAF, these including Australians, Canadians, New Zealanders, Rhodesians and South Africans. In addition, there were other nationalities represented, including Free French, Belgian and a Jewish pilot from the British mandate of Palestine.

These welcome additions were further bolstered by the arrival of fresh Czechoslovak and Polish squadrons. These had been held back by Dowding, who thought non-English speaking aircrew would have trouble working within his control system: Polish and Czechoslovak pilots proved to be especially effective. The pre-war Polish air force had benefited from lengthy and extensive training programmes, and had high standards. With Poland conquered and under German occupation, the pilots of No. 303 (Polish) Squadron, the highest-scoring allied unit, were strongly motivated. Josef Frantisek, a Czech regular who had flown from the occupation of his own country to join the Polish and then French air forces before arriving in the UK, flew as a guest of No. 303 Squadron and was ultimately credited with the highest 'RAF score' in the 'Battle of Britain'.

One of the most important advantages which the RAF enjoyed was the advantage of fighting over home territory. Pilots who bailed out of their crippled aircraft could be back at their airfields within hours, while if low on fuel and/or ammunition they could be immediately refuelled and/or rearmed. For the Luftwaffe, on the other hand, bailing out over England meant capture: in the critical August period, almost exactly as many Luftwaffe pilots were taken prisoner as were killed. Moreover, descend into the English Channel by parachute often meant drowning or death from exposure. In these circumstances, German morale began to suffer, and Kanalkrankheit (channel sickness), which was a form of combat fatigue, began to appear in the ranks of German pilots. Their replacement problem became even worse than it was for the British.

The effect of the German attacks on airfields is unclear. In a letter to Trenchard, and accompanying Park’s report on the period from 8 August to 10 September, Dowding stated that the Luftwaffe 'achieved very little' in the last week of August and the first week of September. The only Sector station to be shut down operationally was Biggin Hill, and then it was non-operational for only two hours. Dowding admitted that No. 11 Group’s efficiency had been impaired but, despite serious damage to some airfields, only two out of 13 heavily attacked airfields were non-operational for more than a few hours. The German refocus on London was not critical.

It has been argued, with some plausibility, that with regard to single-seat fighters not only was British aircraft production replacing aircraft, but replacement pilots were keeping pace with losses. The number of pilots in RAF Fighter Command increased during July, August and September. The figures indicate the number of pilots available never decreased: from July, 1,200 were available, and from 1 August, 1,400 were available. Just over that number were in the field by September. In October the figure was nearly 1,600. By 1 November 1,800 were available. Throughout the battle, the RAF had more fighter pilots available than the Luftwaffe. Although the RAF’s reserves of single-seat fighters fell during July, the wastage was more than offset by an efficient Civilian Repair Organisation, which by December had repaired and put back into service some 4,955 aircraft, and by aircraft held at Air Servicing Unit airfields.

The Germans never had more than between 1,100 and 1,200 single-seat fighter pilots, a deficiency of up to one-third, and it has been stated that 'If Fighter Command were ''the few'', the German fighter pilots were fewer.'

However, other historians have argued that this period was the most dangerous of all, and that the two weeks from 24 August to 6 September represented a real danger. According to this assessment, from 24 August to 6 September 295 fighters were destroyed and 171 badly damaged, against a total output of 269 new and repaired Spitfire and Hurricane fighters. It is asserted that 103 pilots were killed or missing and 128 wounded, which represented a total wastage of 120 pilots per week out of a fighting strength of just fewer than 1,000. It is also asserted that during August no more than 260 fighter pilots were turned out by Operational Training Units, and that casualties in the same month were just over 300. A full squadron establishment was 26 pilots, whereas the average in August was 16. In this assessment, the RAF was losing the battle. Aircraft availability was also a serious issue. While its reserves during the 'Battle of Britain' never declined to a mere half dozen aircraft, as some writers later claimed, the period between 24 August and 6 September had been described as the critical period as, during these two weeks, Germany destroyed far more aircraft through its attacks on No. 11 Group’s bases on the English south-east that the UK was producing. Three more weeks of such a pace would indeed have exhausted aircraft reserves. Germany had also seen heavy losses of pilots and aircraft, thus its shift to night-time attacks in September. On 7 September RAF aircraft losses fell below British production and remained so until the end of the war.

Hitler’s Führerweisung Nr 17 (For the Conduct of Air and Sea Warfare against England), which was issued on 1 August, reserved to himself the right to decide on terror attacks as measures of reprisal. Hitler issued a directive that London was not to be bombed save on his sole instruction. In preparation, detailed target plans under the codename 'Loge', detailing for raids on communications, power stations, armaments works and docks in the Port of London were distributed to the various Fliegerkorps in July. The port areas were right beside residential housing, and civilian casualties were therefore to be expected, but this would combine military and economic targets with indirect effects on morale. The strategy agreed on 6 August was for raids on military and economic targets in towns and cities to culminate in a major attack on London. In the middle of August, raids were made on targets on the outskirts of London.

Luftwaffe doctrine included the possibility of retaliatory attacks on cities, and since 11 May small-scale night raids by RAF Bomber Command had frequently bombed German residential areas. The Germans assumed this was deliberate and, as the raids increased in frequency and scale, the German population grew impatient for retaliatory measures. On 25 August 1940, 81 RAF Bomber Command aircraft were despatched to raid industrial and commercial targets in Berlin. Cloud prevented accurate identification and the bombs fell across the city, causing some casualties among the civilian population as well as damage to residential areas. Continuing RAF raids on Berlin led to Hitler withdrawing his directive on 30 August and giving approval to the planned bombing offensive. On 3 September Göring planned that London be bombed on a daily basis, with Kesselring’s enthusiastic support, having received reports the average strength of RAF squadrons was down to five or seven fighters out of a notional 12 and their airfields in the area were out of action. Hitler issued a directive on 5 September for attacks on cities including London. In a widely publicised speech delivered on 4 September, Hitler condemned the bombing of Berlin and presented the planned attacks on London as reprisals. The first daylight raid was titled Vergeltungsangriff (revenge attack).

On 7 September, a massive series of raids involving nearly 400 bombers and more than 600 fighters targeted docks in the East End of London, day and night. The RAF anticipated attacks on airfields and No. 11 Group rose to meet them in greater numbers than the Luftwaffe expected. The first official deployment of No. 12 Group’s 'big wing' took 20 minutes to form, missing its intended target, but encountering another formation of bombers while still climbing. They returned, apologetic about their limited success, and blamed the delay on being scrambled too late.

The German press jubilantly announced that 'one great cloud of smoke stretches tonight from the middle of London to the mouth of the Thames'. Reports reflected the briefings given to crews before the raids: 'Everyone knew about the last cowardly attacks on German cities, and thought about wives, mothers and children. And then came that word ''Vengeance!'" Pilots reported seeing ruined airfields as they flew towards London, appearances which gave the intelligence apparatus the impression of devastated defences. Göring maintained that the RAF was close to defeat, making invasion feasible.

At this moment RAF Fighter Command had been at its lowest ebb, being short of men and aircraft, and the break from airfield attacks allowed the command to recover. No. 11 Group had considerable success in breaking up daytime raids. No. 12 Group repeatedly disobeyed orders and failed to meet requests to protect No. 11 Group’s airfields, but its experiments with increasingly large 'big wings' had some success. The Luftwaffe began to abandon its morning raids, with attacks on London starting late in the afternoon for 57 consecutive nights.

To the Luftwaffe, the most damaging aspect of targeting London was the increased distance involved. The Bf 109E escorts had a limited fuel capacity resulting in a maximum range of only 410 miles (660 km) on internal fuel, and when they arrived they had only 10 minutes of flying time before they had to turn back for home, leaving the bombers undefended by fighter escorts. Its eventual stablemate, the Focke-Wulf Fw 190A, was flying only in prototype form in the middle of 1940, and the first 28 Fw 190 fighters were not delivered until November 1940. The Fw 190A-1 had a maximum range of 585 miles (940 km) on internal fuel, a figure 40% greater than that of the Bf 109E. The Bf 109E-7 corrected this deficiency by adding a ventral ordnance rack under the fuselage to take either a 551-lb (250-kg) SC-250 bomb or a standard 66-Imp gal (300-litre) drop tank to double the range to 820 miles (1325 km), but the ordnance rack was not retrofitted to earlier Bf 109Es until October 1940.

On 14 September, Hitler chaired a meeting with the staff of the Oberkommando der Wehrmacht. Göring was in France directing the decisive battle, so Milch deputised for him. Hitler asked whether or not the German air effort against the UK should be ended. Jeschonnek, the Luftwaffe chief-of-staff, begged for a last chance to defeat the RAF and for permission to launch attacks on civilian residential areas to cause mass panic. Hitler refused the latter, perhaps unaware of how much damage had already been done to civilian targets. He reserved for himself the power to unleash the terror weapon. Instead, political will was to be broken by destroying the British material infrastructure, the weapons industry, and stocks of fuel and food.

On 15 September, two massive waves of German attacks were decisively repulsed by the commitment of every fighter available to No. 11 Group. Sone 60 German and 26 British aircraft were shot down in what has become known as the climax of the 'Battle of Britain'.

Two days after this German defeat, Hitler postponed preparations for the invasion of Britain. Henceforth, in the face of mounting losses in men and aircraft, and the lack of adequate replacements, the Luftwaffe completed its gradual shift from daylight bomber raids and continued with nocturnal bombing.

At the Oberkommando der Wehrmacht meeting of 14 September, Hitler acknowledged that the Luftwaffe had still not gained the air superiority needed for 'Seelöwe' invasion. In agreement with Raeder’s written recommendation, Hitler said the campaign was to intensify regardless of invasion plans: 'The decisive thing is the ceaseless continuation of air attacks.' Jeschonnek proposed attacking residential areas to cause 'mass panic', but this was vetoed by Hitler who, as noted above, reserved to himself the option of terror bombing. British morale was to be broken by the bombing and destruction of of infrastructure, armaments manufacturing, fuel and food stocks. On 16 September, Göring gave the order for this change in strategy, which was to be the first independent strategic bombing campaign, in hopes of a political success in forcing the British to surrender. Hitler hoped it might result in 'eight million going mad' (referring to the population of London in 1940), which would 'cause a catastrophe' for the British. In those circumstances, Hitler said, 'even a small invasion might go a long way'. Hitler was against cancelling the invasion as 'the cancellation would reach the ears of the [British] and strengthen [their] resolve'. On 19 September, Hitler ordered a reduction in work on 'Seelöwe'. He doubted that strategic bombing could achieve its aims, but ending the air war would be an open admission of defeat. He had to maintain the appearance of concentration on defeating the UK, in order to conceal from Iosif Stalin his covert aim to invade the USSR in the late spring/early summer of the following year.

Throughout the battle, most Luftwaffe bombing raids had been delivered at night. The German bombers suffered increasingly unsustainable losses in daylight raids, and the last massive daytime attacks were on 15 September. A raid of 70 bombers on 18 September also suffered badly, and day raids were gradually phased out, leaving the main attacks to be flown at night. RAF Fighter Command still lacked any effective means to intercept night-time raiders, for the night fighter force comprised mostly Blenheim and Bristol Beaufighter twin-engined aircraft that lacked airborne radar and thus possessed no practical way of finding the bombers. Anti-aircraft guns were diverted to London’s defences, but had a much-reduced success rate against night attacks.

From the middle of September, the Luftwaffe’s daylight bombing role was gradually assumed by Bf 109 fighters adapted to carry one 551-lb (250-kg) bomb. Small groups of these fighter-bombers flew Störangriffe raids escorted by large escort formations of about 200 to 300 fighters. They flew at altitudes over 19,685 ft (6000m), at which the Bf 109 had an advantage over the Hurricane but not the Spitfire. The raids disturbed civilians, and continued the war of attrition against RAF Fighter Command. It was intended that the raids undertake precision bombing of military or economic targets, but it was hard to achieve sufficient accuracy with a single bomb. Moreover, when attacked, the fighter-bombers had to jettison their bombs to defend themselves as fighters. The RAF was at a disadvantage and changed defensive tactics by introducing Spitfire standing patrols at high altitude to monitor incoming raids. On a sighting, other patrols at lower altitude would fly up to join the battle.

The German bombing of the UK reached its peak in October and November 1940. In post-war interrogation, Generalfeldmarschall Wilhelm Keitel, head of the Oberkommando der Wehrmacht, described the aims as economic blockade, in conjunction with U-boat warfare, and attrition of the UK’s military and economic resources. The Luftwaffe desired to achieve victory on its own and was reluctant to co-operate with the navy. Their strategy for the blockade was to destroy ports and storage facilities in towns and cities. Priorities were based on the pattern of trade and distribution, so for these months, London was the main target. In November their attention turned to other ports and industrial targets around the UK.

As noted above, Hitler postponed the 'Seelöwe' invasion on 13 October 'until the spring of 1941'. It was not until Hitler’s Führerweisung Nr 21 was issued, on 18 December, that the threat of a German invasion of the UK finally ended.

During the 'Battle of Britain', and indeed for the rest of the war, an important factor in keeping public morale high was the continued presence in London of King George VI and his wife Queen Elizabeth. When war broke out in 1939, the king and queen had decided to stay in London and not relocate to Canada as had been suggested. The king and queen officially remained in Buckingham Palace throughout the war, although they often spent weekends at Windsor Castle to visit their daughters. Buckingham Palace was damaged by bombs which landed in the grounds on 10 September and, on 13 September, more serious damage was caused by two bombs which destroyed the Royal Chapel. The king and queen were in a small sitting room about 80 yards (73 m) from the bomb detonations.

Overall, by 2 November the RAF fielded 1,796 pilots, an increase of over 40% from July 1940’s count of 1,259 pilots. German sources show German fighter and bomber strengths declined without recovery, and that from August to December 1940, the German fighter and bomber strength declined by 30 and 25% respectively. Another source claims that the Germans had 1,380 bombers on strength on 29 June, 1,420 on 28 September, 1,423 level bombers on 2 November and 1,393 bombers on 30 November. Between July and September the number of Luftwaffe pilots available fell by 136, but the number of operational pilots had shrunk by 171 by September. The training organisation of the Luftwaffe was failing to replace losses. German fighter pilots, in contrast to popular perception, were not afforded training or rest rotations, unlike their British opponents. The first week of September accounted for 25% of Fighter Command’s and 24% of the Luftwaffe’s overall losses. Between 26 August and 6 September, only on 1 September did the Germans destroy more aircraft than they lost. Overall losses were 325 German and 248 British.

Luftwaffe losses for August numbered 774 aircraft to all causes, representing 18.5% of all combat aircraft at the beginning of the month. RAF Fighter Command’s losses in August were 426 fighters destroyed, amounting to 40% of 1,061 fighters available on 3 August. In addition, 99 German bombers and 27 other types were destroyed between 1 and 29 August.

From July to September, the Luftwaffe’s loss records indicate the loss of 1,636 aircraft, 1,184 to enemy action. This represented 47% of the initial strength of single-engined fighters, 66% of twin-engined fighters and 45% of bombers. This indicates the Germans were running out of aircrew as well as aircraft.

Throughout the 'Battle of Britain', the Germans greatly underestimated the size of the RAF and the scale of British aircraft production. Across the English Channel, the Air Intelligence division of the Air Ministry consistently overestimated the size of the German air forces and the productive capacity of the German aviation industry. As the battle was fought, both sides exaggerated the losses inflicted on the other by an equally large margin. The intelligence picture formed before the battle encouraged the Luftwaffe to believe that such losses pushed RAF Fighter Command to the very brink of defeat, while the exaggerated picture of German air strength persuaded the RAF that the threat it faced was larger and more dangerous than was actually the case. This led the British to the conclusion that another fortnight of attacks on airfields might force RAF Fighter Command to pull its squadrons from the south of England. The German misconception, on the other hand, encouraged first complacency, then strategic misjudgement. The shift of targets from air bases to industry and communications was taken because it was assumed that RAF Fighter Command had, in essence, been eliminated as a fighting force.

Between 24 August and 4 September, German serviceability rates, which were acceptable at Ju 87 units, were running at 75% for the Bf 109, 70% for the bombers and 65% for the Bf 110, indicating a shortage of spare parts. All units were well below establishment strength. The attrition was beginning to affect the fighters in particular. By 14 September, the Luftwaffe’s Bf 109 Geschwadern possessed only 67% of their operational crews against authorised aircraft. For Bf 110 units it was 46%, and for bombers 59%. A week later the figures had dropped to 64%, 52% and 52% respectively. Serviceability rates in RAF Fighter Command’s fighter squadrons, between 24 August and 7 September, were listed as 64.8% on 24 August, 64.7% on 31 August and 64.25% on 7 September.

As a result of the Luftwaffe’s failure to establish air supremacy over the UK, a conference assembled on 14 September at Hitler’s headquarters. Hitler concluded that air superiority had not yet been established and promised to review the situation on 17 September for possible landings on 27 September or 8 October. Three days later, when the evidence was clear that the Luftwaffe had greatly exaggerated the extent of its successes against the RAF, Hitler postponed 'Seelöwe' indefinitely.

Propaganda was an important element of the air war which began to develop over the UK from 18 June 1940, when the Luftwaffe began small, probing daylight raids to test RAF defences. Into a time early in July, the British media’s focus on the air battles increased steadily, the press, magazines, BBC radio and newsreels daily conveying the contents of Air Ministry communiqués. In Germany, Oberkommando der Wehrmacht communiqués matched the British efforts in claiming the upper hand.

Central to the propaganda war on both sides of the English Channel were claims for aircraft shot down. These daily claims were important both for sustaining British home front morale and persuading the USA to support the UK, and were produced by the Air Ministry’s Air Intelligence branch. Under pressure from US journalists and broadcasters to prove that the RAF’s claims were genuine, RAF intelligence compared pilots' claims with actual aircraft wrecks and those seen to crash into the sea. It was soon realised that there was a discrepancy between the two, but the Air Ministry decided not to reveal this. In fact, it was not until May 1947 that the actual figures were released to the public, by which time it was of far less importance.

The place of the 'Battle of Britain' in British popular memory stems in part from the Air Ministry’s successful propaganda campaign in the period between July and October 1940, and its praise of the defending pilots courage from March 1941 onward. The third The Battle of Britain pamphlet sold in huge numbers internationally, leading even Goebbels to admire its propaganda value. Focusing only upon the fighter pilots, with no mention of RAF bomber attacks against invasion barges, the 'Battle of Britain' was soon established as a major victory for RAF Fighter Command.

The 'Battle of Britain' marked the first major defeat of Germany’s military forces, with air superiority seen as the key to victory. Pre-war theories had led to exaggerated fears of strategic bombing, and UK public opinion was therefore buoyed by having come through the ordeal. For the RAF, Fighter Command had achieved a great victory in successfully carrying out Inskip’s 1937 air policy of preventing the Germans from knocking the UK out of the war.

The battle also significantly shifted US opinion. During the battle, many Americans accepted the view promoted by Joseph P. Kennedy, the anti-British US ambassador in London, who believed that the UK could not survive. Roosevelt wanted a second opinion, and sent William J. Donovan as an unofficial emissary on a brief visit to the UK: Donovan became convinced that the UK would survive and should be supported in every possible way. Before the end of the year, US journalist Ralph McA. Ingersoll, after returning from the UK, published a book concluding that 'Adolf Hitler met his first defeat in eight years' in what might 'go down in history as a battle as important as Waterloo or Gettysburg'. The turning point was when the Germans reduced the intensity of the 'Blitz' after 15 September. According to Ingersoll, '[a] majority of responsible British officers who fought through this battle believe that if Hitler and Göring had had the courage and the resources to lose 200 planes a day for the next five days, nothing could have saved London', and that instead '[the Luftwaffe’s] morale in combat is definitely broken, and the RAF has been gaining in strength each week.'

Each side made exaggerated claims of numbers of aircraft it had shot down. In general, claims were two to three times the actual numbers. Post-war analysis shows that between July and September the RAF pilots claimed 2,698 Luftwaffe kills, while the Luftwaffe pilots claimed 3,198 RAF aircraft downed. Total losses, and start and end dates for recorded losses, vary for each side. Luftwaffe losses from 10 July to 30 October 1940 totalled 1,977 aircraft, including 243 twin- and 569 single-engined fighters, 822 bombers and 343 non-combat types. In the same period, RAF Fighter Command aircraft losses totalled 1,087, including 53 twin-engined fighters. To the RAF figure must be added 376 RAF Bomber Command and 148 RAF Coastal Command aircraft lost on bombing, mining, and reconnaissance sorties.

It is clear that the strategy of Dowding and Park of choosing when to engage the Germans while maintaining a coherent force is vindicated. However, the two men’s leadership, and the subsequent debates about strategy and tactics, created enmity among senior RAF commanders and both were removed from their positions in the immediate aftermath of the battle. All things considered, the RAF proved to be a robust and capable organisation that was to use all the modern resources available to it to the maximum advantage.

The Germans had delivered some spectacular attacks against important British industries, but they had not managed to destroy the British industrial potential, and made little systematic effort to do so. Hindsight does not disguise the fact the threat to RAF Fighter Command was very real, and for the participants it seemed as if there was a narrow margin between victory and defeat. Nevertheless, even if the German attacks on No. 11 Group’s airfields, which guarded south-eastern England and the approaches to London, had continued, the RAF could have withdrawn to the Midlands out of German fighter range and continued the battle from there.

The British victory in the 'Battle of Britain' had been achieved only at a heavy cost. The total British civilian losses from July to December 1940 were 23,002 dead and 32,138 wounded, with one of the largest single raids on 19 December 1940, in which almost 3,000 civilians died. After the culmination of the German concentrated daylight raids and their switch to nocturnal efforts, the UK was able to rebuild its military forces and establish itself as an Allied stronghold, later serving as a base from which the liberation of North-Western Europe was launched in 1944.