'The Blitz' was a German strategic bombing campaign against the UK (7 September 1940/11 May 1941).

The term was first used by the British press and originated from the German word Blitzkrieg (lightning war).

In 'The Britz', German warplanes undertook mass air attacks against British industrial targets, towns, and cities, beginning with raids on London toward the end of the 'Battle of Britain' in 1940 and which was an air campaign designed to secure German air superiority over the UK. By September 1940, the Luftwaffe had lost the 'Battle of Britain' and the Luftflotten (air fleets) were ordered to attack London in order to draw Air Chief Marshal Sir Hugh Dowding’s RAF Fighter Command into a battle of annihilation. Adolf Hitler and Reichsmarschall Hermann Göring, the German leader and the Luftwaffe’s commander-in-chief respectively, ordered the new policy on 6 September 1940. From 7 September, London was systematically bombed by the Luftwaffe for 56 of the following 57 days and nights. Notable attacks included a large daylight attack on London during 15 September, a substantial raid on 29 December against London resulting in a firestorm known as the Second Great Fire of London, and a major raid on the night of 10/11 May 1941.

The Luftwaffe gradually decreased daylight operations in favour of night attacks to evade attacks by the RAF, and 'The Blitz' became a night bombing campaign after October 1940. The Luftwaffe attacked the main Atlantic seaport of Liverpool in the Liverpool Blitz. The North Sea port of Hull, a convenient and easily found target or secondary target for bombers unable to locate their primary targets, suffered the Hull Blitz. The port cities of Bristol, Cardiff, Portsmouth, Plymouth, Southampton, Swansea, Belfast, and Glasgow were also bombed, as were the industrial centres of Birmingham, Coventry, Manchester, and Sheffield. More than 40,000 civilians were killed by Luftwaffe bombing during the war, almost half of them in the capital, where more than one million houses were destroyed or damaged.

Early in July 1940, the German high command had started to plan the 'Barbarossa' invasion of the USSR. Bombing failed to demoralise the British into surrender or do much damage to the war economy: eight months of bombing never seriously hampered British war production, which continued to increase. The greatest effect of the bombing was to persuade the British to disperse the production of aircraft and spare parts. British wartime studies concluded that most cities took 10 to 15 days to recover when hit severely, but some targets, such as Birmingham, took three months.

The German air offensive failed because the Oberkommando der Luftwaffe develop no methodical strategy for the destruction of British war industries. Poor intelligence about British industry and economic efficiency led the Oberkommando der Luftwaffe to concentrate on tactics rather than strategy. The bombing effort was diluted by attacks against several sets of industries instead of constant pressure on the most vital.

During the 1920s and 1930s, air power theorists such as Giulio Douhet and William Mitchell claimed that air forces could win wars, obviating the need for land and sea combat. It came to believed that 'the bomber will always get through' and could not be resisted, particularly at night. Industry, seats of government and communications could be destroyed, depriving an opponent of the means to make war. Bombing civilians would cause a collapse of morale and a loss of production in the remaining factories. Democracies, where public opinion was allowed, were thought particularly vulnerable. The Royal Air Force and the US Army Air Corps (later the US Army Air Forces) adopted much of this apocalyptic thinking. The policy of RAF Bomber Command became an attempt to achieve victory through the destruction of civilian will, communications and industry.

The Luftwaffe took a cautious view of strategic bombing but the Oberkommando der Luftwaffe did not oppose the strategic bombardment of industries or cities. It believed it could greatly affect the balance of power on the battlefield by disrupting production and damaging civilian morale. The Oberkommando der Luftwaffe did not believe that air power alone could be decisive and the Luftwaffe did not adopt an official policy of the deliberate bombing of civilians until 1942.

The vital industries and transport centres that would be targeted for destruction or complete dislocation were valid military targets. It could be claimed civilians were not to be targeted directly, but the breakdown of production would affect their morale and will to fight. German legal scholars of the 1930s carefully worked out guidelines for what type of bombing was permissible under international law. While direct attacks against civilians were ruled out as 'terror bombing', the concept of attacking vital war industries (with probable heavy civilian casualties and breakdown of civilian morale) was deemed acceptable.

From the beginning of the Nazi régime in 1933 until 1939, there was a debate in German military journals over the role of strategic bombing: some contributors argued along the lines of the British and Americans, and Generalleutnant Walther Wever, the chief of the Luftwaffe general staff between 1 March 1935 and his death in an air accident on 3 June 1936, championed the concept of strategic bombing and the building of the necessary aircraft, although he emphasised the importance of aviation in operational and tactical terms. Wever outlined five points of air strategy: firstly, to destroy an enemy’s air force by bombing its bases and aircraft factories and to defeat enemy air forces attacking German targets; secondly, to prevent the movement of large enemy ground forces to the decisive areas by destroying railways and roads, particularly bridges and tunnels, which are indispensable for the movement and supply of forces; thirdly, to support the operations of the army formations, independent of railways, i.e. armoured forces and motorised forces, by impeding the enemy’s advance and participating directly in ground operations' fourthly, to support naval operations by attacking the enemy’s naval bases, protecting German naval bases and participating directly in naval battles; and fifthly, to paralyse the enemy’s armed forces by stopping production in armaments factories.

Wever argued that the Oberkommando der Luftwaffe should be educated not exclusively in tactical and operational matters but also in grand strategy, war economics, armament production and the mentality of potential opponents. Wever’s vision was not realised, staff studies in those subjects fell by the wayside and the air academies focused on tactics, technology and operational planning, rather than on independent strategic air offensives.

With Wever’s death in 1936, the failure to implement his vision for the new Luftwaffe was largely attributable to his successors. Ex-army personnel and his successors as chief-of-staff, Generalleutnant (soon General) Albert Kesselring (3 June 1936/31 May 1937) and Generalleutnant (soon General) Hans-Jürgen Stumpff (1 June 1937/31 January 1939) are usually blamed for the abandonment of strategic planning as they favoured the Luftwaffe’s capabilities in the close air support and other tactical roles.

Two prominent enthusiasts for ground support operations (direct or indirect) were Generalleutnant (soon General) Hugo Sperrle, the commander of Luftflotte III (1 February 1939/23 August 1944) and Generalleutnant (soon General) Hans Jeschonnek, the chief of the Luftwaffe general staff (1 February 1939/19 August 1943). The Luftwaffe was not pressed into ground support operations by pressure from the army or because it was led by ex-soldiers, but rather because the Luftwaffe favoured a model of joint inter-service operations, rather than independent strategic air campaigns.

Hitler paid less attention to the bombing of opponents than air defence, although he promoted the development of a bomber force in the 1930s and understood it was possible to use bombers for strategic purposes. He told the Oberkommando der Luftwaffe in 1939 that ruthless employment of the Luftwaffe against the heart of the British will to resist would follow when the moment was right. Hitler quickly developed scepticism toward strategic bombing, confirmed by the results of 'The Blitz'. He frequently complained of the Luftwaffe’s inability to damage industries sufficiently, saying that 'The munitions industry cannot be impeded effectively by air raids…usually, the prescribed targets are not hit.'[

While the war was being planned, Hitler never insisted upon the Luftwaffe planning a strategic bombing campaign and did not even give ample warning to the air staff that war with the UK or USSR was a possibility. The amount of firm operational and tactical preparation for a bombing campaign was minimal, largely because of the failure by Hitler as supreme commander to insist upon such a commitment.

Ultimately, Hitler was trapped within his own vision of bombing as a terror weapon, formed in the 1930s when he threatened smaller nations into accepting German rule rather than submit to air bombardment. This had important implications. It showed the extent to which Hitler mistook Allied strategy for one of morale breaking instead of one of economic warfare, with the collapse of morale as a bonus.

Hitler was much more attracted to the political aspects of bombing. As the mere threat of it had produced diplomatic results in the 1930s, he expected that the threat of German retaliation would persuade the Allies to adopt a policy of moderation and not to begin a policy of unrestricted bombing. For reasons of political prestige within Germany itself, his hope was that the German population would be protected from the Allied bombings. When this proved impossible, he began to fear that popular feeling would turn against his régime, and redoubled efforts to mount a similar 'terror offensive' against the UK in order to produce a stalemate in which both sides would hesitate to use bombing at all.

A major problem in the management of the Luftwaffe was Göring. Hitler believed the Luftwaffe was 'the most effective strategic weapon', and in reply to repeated requests from the Kriegsmarine for control over naval aircraft insisted that 'We should never have been able to hold our own in this war if we had not had an undivided Luftwaffe.' Such principles made it considerably more difficult to integrate the air force into the overall strategy, and produced in Göring a jealous and damaging defence of his 'empire' while removing Hitler voluntarily from the systematic direction of the Luftwaffe at either the strategic or operational level. When Hitler tried to intervene more in the running of the air force later in the war, he was faced with a political conflict of his own making between himself and Göring, which was not fully resolved until the war was almost over. In 1940 and 1941, Göring’s refusal to co-operate with the Kriegsmarine denied the entire military forces of the Reich the chance to strangle British sea communications, which might have had a strategic or decisive effect in the war against the British empire.

The deliberate separation of the Luftwaffe from the rest of the military structure encouraged the emergence of a major 'communications gap' between Hitler and the Luftwaffe, which other factors helped to exacerbate. For one thing, Göring’s fear of Hitler led him to falsify or misrepresent what information was available in the direction of an uncritical and over-optimistic interpretation of air strength. When Göring decided against continuing Wever’s original heavy bomber programme in 1937, his own explanation was that Hitler wanted to know only how many bombers there were, not how many engines each had. In July 1939, Göring arranged a display of the Luftwaffe’s most advanced equipment at Rechlin, to give the impression the air force was more prepared for a strategic air war than was actually the case.

Although not specifically prepared to conduct independent strategic air operations, the Luftwaffe was expected to do just this over the UK. From July to September 1940, the Luftwaffe attacked RAF Fighter Command to gain air superiority as a prelude to invasion. This involved the bombing of English Channel convoys, ports, and RAF airfields and supporting industries. Destroying RAF Fighter Command would allow the Germans to gain control of the skies over the invasion area. It was supposed that RAF Bomber Command, RAF Coastal Command and the Royal Navy could not operate under conditions of German air superiority.

The Luftwaffe’s poor intelligence meant that its aircraft were not always able to locate their targets, and thus attacks on factories and airfields failed to achieve the desired results. British fighter aircraft production continued at a rate surpassing Germany’s by 2/1: the British constructed 10,000 aircraft in 1940, whereas the Germans built just 8,000. The replacement of pilots and aircrew was still more difficult. Both the RAF and Luftwaffe struggled to replace manpower losses, though the Germans had larger reserves of trained aircrew. The circumstances affected the Germans more than the British. Operating over home territory, British aircrew could fly again if they survived being shot down. German crews, even if they survived, faced capture. Moreover, bombers had four to five crewmen on board, representing a greater loss of manpower. On 7 September, the Germans shifted away from the destruction of the RAF’s supporting structures. German intelligence suggested that RAF Fighter Command was weakening, and that an attack on London would force it into a final battle of annihilation while compelling the British government to surrender.

The decision to change strategy is sometimes claimed as a major mistake by the Oberkommando der Luftwaffe. It is argued that persisting with attacks on RAF airfields might have won air superiority for the Luftwaffe. Others argue that the Luftwaffe made little impression on RAF Fighter Command in the last week of August and first week of September, and that the shift in strategy was therefore not decisive. It has also been argued that it was doubtful that the Luftwaffe could have won air superiority before the required 'weather window' began to close in October.

It was also possible, should its losses become severe, that the RAF could have pulled back to the north, await the German invasion, then redeploy to the south once again. Other historians argue that the outcome of the air battle was irrelevant; the massive numerical superiority of British naval forces and the inherent weakness of the Kriegsmarine would have made the projected 'Seelöwe' invasion a disaster with or without German air superiority.

Regardless of the ability of the Luftwaffe to win air superiority, Hitler was frustrated that it was not happening quickly enough. With no sign of the RAF weakening and the Luftflotten suffering heavy losses, the Oberkommando der Luftwaffe was keen for a change in strategy. To reduce losses further, strategy changed from day to night raids, the darkness giving the bombers greater protection.

It was decided to focus on bombing Britain’s industrial cities, initially in daylight. The main focus was London. The first major raid took place on 7 September. On 15 September, on a date now known as Battle of Britain Day, a large-scale raid was launched in daylight, but suffered significant loss for no lasting gain. Although there were a few large air battles fought in daylight later in the month and into October, the Luftwaffe switched its main effort to night attacks. This became official policy on 7 October. The air campaign soon got under way against London and other British cities.

However, the Luftwaffe faced limitations. Its aircraft, namely the Dornier Do 17, Heinkel He 111 and Junkers Ju 88 twin-engined medium bombes were capable of carrying out strategic missions but were nonetheless incapable of inflicting greater damage because of their modest bombloads. The Luftwaffe’s decision in the interwar period to concentrate on medium bombers can be attributed to several reasons: Hitler did not intend or foresee a war with the UK in 1939, the Oberkommando der Luftwaffe believed that a medium bomber force could carry out strategic missions just as well as a heavy bomber force, and Germany did not possess the resources or technical ability to produce four-engined bombers before the war.

Although it had equipment capable of inflicting major damage, the Luftwaffe was further hampered by its retention of an unclear strategy and its poor intelligence. The Oberkommando der Luftwaffe had not been informed that the UK was to be considered a potential opponent until a time early in 1938. It had no time to gather reliable intelligence on the UK’s industries. Moreover, the Oberkommando der Luftwaffe could not settle on an appropriate strategy. German planners had to decide whether the Luftwaffe should deliver the weight of its attacks against a specific segment of British industry, such as aircraft factories, or against a system of interrelated industries such as the UK’s import and distribution network, or even in a blow aimed at breaking the morale of the British population. The Luftwaffe’s strategy became increasingly aimless over the winter of 1940/1941, and disputes among the Oberkommando der Luftwaffe's staff revolved more around tactics than strategy. This condemned the offensive over the UK to failure even before it had begun.

In an operational capacity, limitations in weapons technology and quick British reactions were making it more difficult to achieve strategic effect. Attacking ports, shipping and imports as well as disrupting railway traffic in the surrounding areas, especially the distribution of coal, an important fuel in all industrial economies of World War II, would net a positive result. However, the use of delayed-action bombs, while initially very effective, gradually had less impact, partly because they often failed to detonate. The British had anticipated the change in strategy and dispersed their production facilities, making them less vulnerable to a concentrated attack. Regional commissioners were given plenipotentiary powers to restore communications and organise the distribution of supplies to keep the war economy moving.

London had nine million people, about one-fifth of the British population, living in an area of 750 sq miles (1940 km²), which was difficult to defend because of its very size. Based on experience with German strategic bombing of the UK during World War I, the British government estimated that 50 casualties, of whom about one-third would be killed, would result for every ton of bombs dropped on London. The estimate of the number of tons of bombs an opponent could drop every day grew as aircraft technology advanced, from 75 in 1922, to 150 in 1934 and to 644 in 1937.

In 1937 the Committee on Imperial Defence estimated that an attack of 60 days would result in 600,000 dead and 1.2 million wounded. News reports of the Spanish Civil War, such as the bombing of Barcelona, supported the estimate of 50 casualties per ton. By 1938, experts generally expected that Germany would try to drop as much as 3,500 tons in the first 24 hours of war and average 700 tons a day for several weeks. It was also believed that in addition to high explosive and incendiary bombs, the Germans could use poison gas and even bacteriological warfare, all with a high degree of accuracy. In 1939 the military theorist Basil Liddell-Hart predicted that 250,000 deaths and injuries could occur in the UK during the first week of war. London hospitals prepared for 300,000 casualties in the first week of war.

British air raid sirens sounded for the first time 22 minutes after Neville Chamberlain, the prime minister, declared war on Germany. Although bombing attacks unexpectedly did not begin immediately during the 'Phoney War', civilians were aware of the lethality of air attacks through newsreels of Barcelona, the bombing of Guernica and the bombing of Shanghai. Many popular works of fiction during the 1920s and 1930s portrayed aerial bombing, such as H. G. Wells’s novel The Shape of Things to Come and its 1936 film adaptation, and others such as The Air War of 1936 and The Poison War.

Based in part on the experience of German bombing in World War I, politicians feared mass psychological trauma from aerial attacks and the collapse of civil society. In 1938, a committee of psychiatrists predicted three times as many mental as physical casualties from aerial bombing, implying three to four million psychiatric patients. In 1934, Winston Churchill told parliament that 'We must expect that, under the pressure of continuous attack upon London, at least three or four million people would be driven out into the open country around the metropolis.' Panic during the Munich crisis, such as the migration by 150,000 people to Wales, contributed to fear of social chaos.

The government planned the evacuation of four million people, mostly women and children, from urban areas, including 1.4 million from London. It expected about 90% of evacuees to stay in private homes, conducted an extensive survey to determine the amount of space available, and made detailed preparations for the transport of evacuees. A trial black-out was held on 10 August 1939 and when Germany invaded Poland on 1 September, a black-out began at sunset. The external exposure of lights was not permitted after dark for almost six years and the black-out became by far the most unpopular aspect of the war for civilians, even more than rationing. The relocation of the government and the civil service was also planned but would only have occurred if necessary so as not to damage civilian morale. Not only was there evacuation over land, but also by ship. The Children’s Overseas Reception Board was organised by the government to help parents send their children overseas to the four British dominions of Canada, Australia, New Zealand and South Africa. The programme evacuated 2,664 boys and girls in the age group between 5 and 15 years until its ending in October after the sinking of the City of Benares with the loss of 81 of the 100 children on board.

Much civil defence preparation in the form of shelters was left in the hands of local authorities, and many areas such as Birmingham, Coventry, Belfast and the East End of London did not have enough shelters. The unexpected delay to civilian bombing during the 'Phoney War' meant that the shelter programme finished in June 1940, before the start of 'The Blitz'. The programme favoured garden Anderson shelters and small brick surface shelters. Many of the latter were abandoned in 1940 as unsafe. Authorities expected that the raids would be brief and in daylight, rather than attacks by night, which forced Londoners to sleep in shelters.

Deep shelters provided most protection against a direct bomb hit. The government did not build such shelters for large populations before the war because of their cost, time to build and fears that their safety would cause occupants to refuse to leave to return to work or that anti-war sentiment would develop in large congregations of civilians. The government saw the leading role taken by the Communist Party in advocating the building of deep shelters as an attempt to damage civilian morale, especially after the Molotov-Ribbentrop Pact of August 1939. The most important existing communal shelters were the stations of the London Underground system. Although many civilians had used them for shelter during World War I, the government in 1939 refused to allow the stations to be used as shelters so as not to interfere with commuter and troop travel and the fears that occupants might refuse to leave. Underground officials were ordered to lock station entrances during raids but by the second week of heavy bombing, the government relented and ordered the stations to be opened. Each day orderly lines of people queued until 16.00, when they were allowed to enter the stations. In the middle of September 1940, about 150,000 people a night slept in the Underground, although by winter and spring the numbers declined to 100,000 or less. Battle noises were muffled and sleep was easier in the deepest stations, but many people were killed from direct hits on stations. In March 1943, 173 men, women and children were crushed to death at Bethnal Green tube station in a crowd surge after a woman fell down the steps as she entered the station. A single direct hit on a shelter in Stoke Newington in October 1940 killed 160 civilians.

Communal shelters never housed more than one-seventh of Greater London’s residents. Peak use of the Underground as shelter was 177,000 on 27 September 1940, and a November 1940 census of London found that about 4% of residents used the Underground and other large shelters, 9% in public surface shelters and 27% in private home shelters, implying that the remaining 60% of the city stayed at home. The government distributed Anderson shelters until 1941, and that year began distributing the Morrison shelter, which could be used inside homes.

Public demand led the government in October 1940 to build new deep shelters within the Underground to hold 80,000 people, but the period of the heaviest bombing had passed before they were finished. By the end of 1940 improvements had been made in the Underground and in many other large shelters. Authorities provided stoves and bathrooms and canteen trains provided food. Tickets were issued for bunks in large shelters, to reduce the amount of time spent queuing. Committees quickly formed within shelters as informal governments, and organisations such as the British Red Cross and the Salvation Army worked to improve conditions. Entertainment included concerts, films, plays and books from local libraries.

Although only a small number of Londoners used the mass shelters, when journalists, celebrities and foreigners visited they became part of the Beveridge Report, part of a national debate on social and class division. Most residents found that such divisions continued within the shelters and many arguments and fights occurred over noise, space and other matters. Anti-Jewish sentiment was reported, particularly around the East End of London, with anti-Semitic graffiti and anti-Semitic rumours, such as that Jewish people were 'hogging' air raid shelters. Contrary to pre-war fears of anti-Semitic violence in the East End, one observer found that the 'Cockney and the Jew [worked] together, against the Indian.'

The intensity of the bombing was not as great as pre-war expectations, so an equal comparison is impossible, and no psychiatric crisis occurred because of 'The Blitz' even during the period of greatest bombing of September 1940. A US witness wrote that 'By every test and measure I am able to apply, these people are staunch to the bone and won’t quit…the British are stronger and in a better position than they were at its beginning.' People referred to raids as if they were weather, stating that a day was or was not 'very blitzy'.

London civilians did not suffer from widespread shell shock, unlike soldiers in the 'Dynamo' evacuation from Dunkirk. The psychoanalysts were correct, and the special network of psychiatric clinics opened to receive mental casualties of the attacks closed for lack of need. Although the stress of the war resulted in many anxiety attacks, eating disorders, fatigue, weeping, miscarriages, and other physical and mental ailments, society did not collapse. The number of suicides and drunkenness declined, and London recorded only about two cases of 'bomb neurosis' per week in the first three months of bombing. Many civilians found that the best way to retain mental stability was to be with family, and after the first few weeks of bombing, avoidance of the evacuation programmes grew.

The cheerful crowds visiting bomb sites were so large that they interfered with rescue work. Pub visits increased in number (beer was never rationed), and 13,000 people attended cricket at Lord’s ground. People left shelters when told instead of refusing to leave, although many housewives reportedly enjoyed the break from housework. Some people even told government surveyors that they enjoyed air raids if they occurred occasionally, perhaps once a week.

Despite the attacks, the defeats in Norway and France, and the threat of invasion, overall morale remained high. A Gallup poll found only 3% of Britons expected to lose the war in May 1940. Another poll found an 88% approval rating for Churchill in July. A third poll found 89% support for his leadership in October. Support for peace negotiations declined from 29% in February. Each setback caused more civilians to volunteer to become unpaid Local Defence Volunteers. Workers worked longer shifts and over weekends. Contributions rose to the £5,000 'Spitfire Funds' to build fighters and the number of work days lost to strikes in 1940 was the lowest in history.

Civilians of London played an enormous role in protecting their city. Many civilians unwilling or unable to join the military joined the Home Guard, the Air Raid Precautions service, the Auxiliary Fire Service and many other civilian organisations. The Auxiliary Fire Service had 138,000 personnel by July 1939. One year earlier, there had only been 6,600 full-time and 13,800 part-time firemen in the entire country. Before the war, civilians were issued with 50 million respirators (gas masks) in case bombardment with gas began before evacuation.

During 'The Blitz', the Scout Association guided fire engines to where they were most needed and became known as the 'Blitz Scouts'. Many unemployed people were drafted into the Royal Army Pay Corps and the Pioneer Corps, and were tasked with salvaging and clean-up. The Women’s Voluntary Services for Civil Defence was established in 1938 by the Home Secretary, Samuel Hoare, who considered it the female branch of the Air Raid Precautions service. The Women’s Voluntary Services organised the evacuation of children, established centres for those displaced by bombing, and operated canteens, salvage and recycling schemes. By the end of 1941, the Women’s Voluntary Services had one million members.

Pre-war dire predictions of mass air raid neurosis were not realised. Predictions had underestimated adaptability and resourcefulness of civilians. There were also many new civil defence roles that gave a sense of fighting back rather than despair. Official histories concluded that the mental health of a nation may have improved, while panic was rare.

In the time since Major General (later Marshal of the Royal Air Force Lord) Hugh Trenchard had commanded the Royal Flying Corps in 1915/17, British air doctrine stressed offence as the best means of defence, and this became known as the cult of the offensive. To prevent German formations from hitting targets in the UK, RAF Bomber Command would destroy Luftwaffe aircraft on their bases, aircraft in their factories and fuel reserves by attacking oil plants. This philosophy proved impractical as RAF Bomber Command lacked the technology and equipment for mass night operations, since resources were diverted to RAF Fighter Command in the middle of the 1930s, and it took until 1943 to catch up. Dowding agreed air defence would require some offensive action and that fighters alone could not defend the UK. Until September 1939, the RAF lacked specialist night-fighting aircraft and relied on anti-aircraft artillery units, which were poorly equipped and lacking in numbers.

The attitude of the Air Ministry was in contrast with the experiences of World War I, when German bombers caused physical and psychological damage out of all proportion to their numbers. Around 250 tons (9,000 bombs) had been dropped, killing 1,413 people and injuring 3,500 more. Many people over 35 remembered the bombing and were afraid of more. From 1916 to 1918, German raids had diminished against countermeasures which demonstrated defence against night air raids was possible. Although night air defence was causing greater concern before the war, it was not at the forefront of RAF planning after 1935, when funds were directed into the new ground-based radar day fighter interception system. The difficulty of RAF bombers in night navigation and target finding led the British to believe that it would be the same for German bomber crews. There was also a mentality in all air forces that flying by day would obviate the need for night operations and their inherent disadvantages.

Under Dowding’s leadership, RAF Fighter Command efeated the Luftwaffe in the 'Battle of Britain', but preparing day fighter defences had left little for night air defence. When the Luftwaffe struck at British cities for the first time on 7 September 1940, a number of civic and political leaders were worried by Dowding’s apparent lack of reaction to the new crisis. Dowding accepted that, as the defensive air commander, he was responsible for the night as well as day defence of the UK, but seemed reluctant to act quickly and his critics in the Air Staff felt that this was due to his stubborn nature. Dowding was summoned on 17 October, to explain the poor state of the night defences and the supposed (but ultimately successful) 'failure' of his daytime strategy. The Minister of Aircraft Production, Lord Beaverbrook, and Churchill distanced themselves. The failure to prepare adequate night air defences was undeniable but it was not the responsibility of the head of RAF Fighter Command to dictate the disposal of resources. The general neglect of the RAF, until the late spurt in 1938, left few resources for night air defence and the government, through the Air Ministry and other civil and military institutions, was responsible for policy. Before the war, the Chamberlain government stated that night defence from air attack should not take up much of the national effort.

Because of the inaccuracy of celestial navigation for night navigation and target finding in fast-flying aircraft, the Luftwaffe developed radio navigation devices and relied on three systems: Knickebein (crooked leg), X-Gerät (X-device) and Y-Gerät (Y-device). This led the British to develop countermeasures in what became known as the 'Battle of the Beams'. Bomber crews already had some experience with the Lorenz beam, a commercial blind-landing aid for night or adverse-weather landings. The Germans adapted the short-range Lorenz system into Knickebein, a 30/33 MHz system, which used two Lorenz beams with much stronger signals. Two antennae at ground stations were traversed so that their beams intersected over the selected target. The German bombers would fly along either beam until they picked up the signal from the other beam. When a continuous sound was heard from the second beam the crew knew they were above the target and dropped their bombs.

Knickebein was in general use but the X-Gerät was reserved for specially trained pathfinder crews. X-Gerät receivers were mounted in He 111 aircraft that had a radio mast on the fuselage. The system worked on 66/77 MHz, a higher frequency than Knickebein. Ground transmitters sent pulses at a rate of 180 per minute. X-Gerät received and analysed the pulses, giving the pilot visual and aural directions. Three cross-beams intersected the beam along which the He 111 was flying: the first of these alerted the bomb-aimer, who activated a bombing clock when the second cross-beam was reached, and when the third cross-beam was reached the bomb aimer activated a third trigger, which stopped the first hand of the clock, with the second hand continuing; when the second hand re-aligned with the first, the bombs were released. The clock mechanism was co-ordinated with the distances of the intersecting beams from the target so the target was directly below when the bombs were released.

Y-Gerät was an automatic beam-tracking system and the most complex of the three devices, and was operated through an autopilot. The pilot flew along an approach beam, monitored by a ground controller. Signals from the station were retransmitted by the bomber’s equipment, which allowed the distance the bomber had travelled along the beam to be measured precisely. Direction-finding checks also enabled the controller to keep the pilot on course. The crew would be ordered to drop their bombs either by a code word from the ground controller or at the conclusion of the signal transmissions. The maximum range of Y-Gerät was similar to those of the other systems, and it was accurate enough on occasion for specific buildings to be hit.

In June 1940, a German prisoner of war was overheard boasting that the British would never find the Knickebein, even though it was under their noses. The details of the conversation were passed to an RAF Air Staff technical adviser, Dr R. V. Jones, who started a search which discovered that Luftwaffe Lorenz receivers were more than blind-landing devices. Jones began a search for German beams: Avro Anson twin-engined aircraft of the Beam Approach Training Development Unit, each fitted with a 30-MHz receiver, were flown up and down the UK, and soon a beam was traced to Derby, which had been mentioned in Luftwaffe transmissions. The first jamming operations were carried out using requisitioned hospital electrocautery machines. The counter-operations were carried out by electronic countermeasures units under Wing Commander Edward Addison of the RAF’s No. 80 Wing. The production of false radio navigation signals by retransmitting the originals became known as 'meaconing' using masking beacons ('meacons'). Up to nine special transmitters directed their signals at the beams in a manner that subtly widened their paths, making it harder for bomber crews to locate targets; confidence in the device was diminished by the time the Luftwaffe was ready to conduct major raids.

German beacons operated on the medium-frequency band and the signals involved a two-letter Morse identifier followed by a lengthy time-lapse which enabled the Luftwaffe crews to determine the signal’s bearing. The 'meacon' system involved separate locations for a receiver with a directional aerial and a transmitter. The receipt of the German signal by the receiver was duly passed to the transmitter, the signal to be repeated. The action did not guarantee automatic success. If the German bomber flew closer to its own beam than the 'meacon' then the former signal would come through more strongly on the direction finder, and the reverse would apply only if the 'meacon' was closer. In general, German bombers were likely to get through to their targets without too much difficulty.

It was to be some months before an effective night-fighter force would be ready, and anti-aircraft defences only became adequate after 'The Blitz' was over, so ruses were created to lure German bombers away from their targets. Throughout 1940, dummy airfields were prepared, good enough to stand up to skilled observation. An unknown number of bombs fell on these diversionary ('Starfish') targets. For industrial areas, fires and lighting were simulated. It was decided to recreate normal residential street lighting, and in non-essential areas, lighting to recreate heavy industrial targets. In those sites, carbon arc lamps were used to simulate flashes at tram overhead wires. Red lamps were used to simulate blast furnaces and locomotive fireboxes. Reflections made by factory skylights were created by placing lights under angled wooden panels. The use of diversionary techniques such as fires had to be undertaken carefully. The fake fires could only begin when the bombing started over an adjacent target and its effects had been brought under control. If the false fires were lit too soon, the chances of success receded; too late and the real conflagration at the target would exceed the diversionary fires. Another innovation was the boiler fire. These units were fed from two adjacent tanks containing oil and water. The oil-fed fires were then injected with water from time to time; the flashes produced were similar to those of the German C-250 and C-500 Flammbomben (incendiary bombs). The hope was that, if it could deceive German bomb-aimers, it would draw more bombers away from their real targets.

The first deliberate air raids on London were directed primarily against the Port of London and caused severe damage. Late in the afternoon of 7 September 1940, the Germans began 'Loge' and 'Seeschlange', the air offensives against London and other industrial cities. 'Loge' continued for 57 nights, and on the first day day 348 bombers and 617 fighters took part in the attack.

Initially, the change in strategy caught the RAF off-guard and caused extensive damage and civilian casualties. Some 107,400 tons of shipping were damaged in the Thames estuary and 1,600 civilians became casualties, of whom some 400 were killed. The fighting in the air was more intense in daylight. 'Loge' cost the Luftwaffe 41 aircraft in the form of 14 bombers, 16 Messerschmitt Bf 109 single-engined fighters, seven Messerschmitt Bf 110 tin-engined heavy fighters, and four reconnaissance aircraft. RAF Fighter Command lost 23 fighters, with six pilots killed and another seven wounded. Another 247 bombers from Luftflotte III attacked that night, and on 8 September the Luftwaffe returned. killing 412 people and severely wounding another 747.

On 9 September the Oberkommando der Luftwaffe appeared to be backing two strategies. Its round-the-clock bombing of London was an immediate attempt to force the British government to capitulate, but it was also striking at the UK’s vital sea communications to achieve a victory through siege. Although the weather was poor, heavy raids took place that afternoon on the London suburbs and the airfield at Farnborough. The day’s fighting cost Kesselring and his Luftflotte II 24 aircraft, including 13 Bf 109 fighters. RAF Fighter Command lost 17 fighters and six pilots. Over the next few days weather was poor and the next main effort was not flown until 15 September.

On 15 September the Luftwaffe made two large daylight attacks on London along the Thames estuary, targeting the city’s docks and railway communications. The German hope was the destruction of the selected targets and the luring of the RAF into their defence, allowing the Luftwaffe to destroy the British fighters in large numbers and thereby achieving air superiority. Large air battles developed, lasting for most of the day. The first attack merely damaged the railway network for three days, and the second attack failed totally. The air battle was later commemorated as Battle of Britain Day. The Luftwaffe lost 18% of the bombers despatched on that day and failed to gain air superiority.

While Göring was optimistic the Luftwaffe could prevail, Hitler was not. On 17 September he postponed 'Seelöwe' (as it turned out indefinitely) rather than gamble Germany’s newly gained military prestige on a risky cross-Channel operation, particularly in the face of a sceptical Iosef in the USSR. In the last days of the battle, the bombers became lures in an attempt to draw the RAF into combat with German fighters. But their operations were to no avail; the worsening weather and unsustainable attrition in daylight gave the Oberkommando der Luftwaffe an excuse to switch to night attacks on 7 October.

On 14 October, the heaviest night attack up to that date saw 380 bombers of Luftflotte III attack London. Some 200 people were killed and another 2,000 injured. The British anti-aircraft artillery defences, under the command of Lieutenant General F. A. Pile) fired 8,326 rounds and shot down a mere two bombers. On 15 October, the bombers returned and about 900 fires were started by the mix of 376 tons of high explosive and 10 tons of incendiaries dropped. Five main railway lines were cut in London and rolling stock was damaged.

'Loge' continued during October, in which 8,200 tons of bombs were dropped , bout 10% in daylight and more than 5,400 tons on London during the night. Birmingham and Coventry were subject to 450 tons of bombs between them in the last 10 days of October. Liverpool received 180 tons of bombs. Hull and Glasgow were attacked, but 715 tons of bombs were spread out all over the UK. The Metropolitan-Vickers works in Manchester was hit by 12 tons of bombs. Little tonnage was dropped on RAF Fighter Command airfields, RAF Bomber Command airfields being targeted instead.

Luftwaffe policy at this point was primarily to continue progressive attacks on London, chiefly by night. secondarily to interfere with production in the vast industrial arms factories of the West Midlands, again chiefly by night attack. and thirdly to disrupt factories and other industrial facilities during the day by means of fighter-bomber attacks.

Kesselring, commanding Luftflotte II, was ordered to send 50 sorties per night against London and attack eastern harbours in daylight, while Sperrle, commanding Luftflotte III, was ordered to dispatch 250 sorties per night including 100 against targets in the West Midlands. 'Seeschlange' was carried out by General Otto Hoffmann von Waldau’s X Fliegerkorps, which concentrated on mining operations against shipping but was also involved in the bombing overthe UK. By 19/20 April 1941, the X Fliegerkorps had dropped 3,984 mines, one-third of the total dropped. The mines' ability to destroy entire streets earned them respect in the UK, but several failed to detonate, and falling into British hands, allowed the development of countermeasures which damaged the German anti-shipping campaign.

By the middle of November 1940, when the Germans adopted a changed plan, more than 11,600 tons of high explosive and nearly one million incendiaries had fallen on London. Outside the British capital, there had been widespread harassing activity by single aircraft, as well as fairly strong diversionary attacks on Birmingham, Coventry and Liverpool, but no major raids. London’s docks and railway communications had taken a heavy pounding, and much damage had been done to the railway system outside the capital. In September, there had been no less than 667 hits on railways in the UK and, at one period, between 5,000 and 6,000 wagons were standing idle from the effect of delayed-action bombs. But the great bulk of the traffic went on, and Londoners, even though they glanced apprehensively each morning at the list of closed stretches of line displayed at their local station, or made strange detours round back streets in the buses, still got to work. For all the destruction of life and property, the observers sent out by the Ministry of Home Security failed to discover the slightest sign of a break in morale. More than 13,000 civilians had been killed and almost 20,000 injured in September and October alone, but the death toll was much less than expected.

Wartime observers perceived the bombing as indiscriminate. On 8 September, both Battersea and West Ham power stations were shut down after the 7 September daylight attack on London. In the case of Battersea power station, an unused extension was hit and destroyed during November but the station was not put out of action during the night attacks. It is not clear whether the power station or any specific structure was targeted during the German offensive as the Luftwaffe could not accurately bomb select targets during night operations. In the initial operations against London, it did appear that railway targets and the bridges over the Thames river had been singled out: Victoria Station was hit by four bombs and suffered extensive damage.The bombing disrupted rail traffic through London but did not destroy any of the crossings. On 7 November, St Pancras, Kensal and Bricklayers Arms stations were hit, and several lines of Southern Rail were cut on 10 November. The British government grew anxious about the delays and disruption of supplies during the month. Reports suggested the attacks blocked the movement of coal to the Greater London regions and urgent repairs were required. Attacks against the East End docks were effective and many Thames barges were destroyed. The London Underground railway system was also affected: high explosive bombs damaged tunnels, rendering some of them unsafe. The London Docklands, and in particular the Royal Victoria Dock, received many hits, and Port of London trade was disrupted. In some cases, the concentration of the bombing and resulting conflagration created firestorms with temperatures of 1,830° F (1000° C). The Ministry of Home Security reported that although the damage caused was 'serious' it was not 'crippling', and the quays, basins, railways and equipment remained operational.

At the start of 'The Blitz', the British night air defences were in a poor state. Few of the anti-aircraft guns had fire-control systems, and the underpowered searchlights were usually ineffective against aircraft at altitudes above 12,000 ft (3660 m). In July 1940, only 1,200 heavy and 549 light guns were deployed in the whole of the UK. Of the heavy guns, some 200 were of the obsolescent 3-in (76.2-mm) type, and the others were of the effective 4.5-in (114.3-mm) and 3.7-in (94-mm) types with a theoretical ceiling of more than 30,000 ft (9145 m) but a practical limit of 25,000 ft (7620 m) because the predictor in use could not accept greater heights. The light guns, about half of which were of the excellent Bofors 40-mm type, could deal with aircraft flying at altitudes of 6,000 ft (1830 m) or less. Although the use of the guns improved civilian morale, with the knowledge the German bomber crews were facing the barrage, it is now believed that the anti-aircraft guns achieved little and in fact the falling shell fragments caused more British casualties on the ground.

Few British fighter aircraft were able to operate at night. Ground-based radar was limited, and airborne radar and RAF night-fighters were generally ineffective. RAF day fighters were converting to night operations and the interim Bristol Blenheim twin-engined night-fighter conversion of the light bomber was being replaced by the powerful Bristol Beaufighter twin-engined night-fighter, but this latter was available only in very small numbers. By the second month of 'The Blitz', it was clear that the defences were not performing well. London’s defences were rapidly reorganised by Pile, commander of the Anti-Aircraft Command. Yet the difference this effected in the efficiency of the air defences is questionable. The British were still one-third below the establishment of heavy anti-aircraft artillery in May 1941, with only 2,631 weapons available. Dowding had to rely on night-fighters. From 1940 to 1941, the most successful night-fighter was the Boulton Paul Defiant single-engined turret fighter: equipping four squadrons, the Defiant shot down more German aircraft than any other type. The anti-aircraft defences were improved by better use of radar and searchlights. Over several months, the 20,000 shells expended per bomber shot down in September 1940 was reduced to 4,087 in January 1941 and to 2,963 in February 1941.

The primitive airborne interception radar of the time was unreliable. The heavy fighting in the 'Battle of Britain' had consumed most of RAF Fighter Command’s resources, so there was little available for investment in night-fighting. As a measure of desperation, bombers were flown with airborne searchlights, but to little avail. Of greater potential was the GL (Gun-Laying) radar and searchlights with fighter direction from RAF fighter control rooms to inaugurate a Ground Control-led Interception technique under group-level control (No. 10 Group, No. 11 Group and No. 12 Group). Whitehall’s disquiet at the failures of the RAF led to the replacement of Dowding, who was already due for retirement, with Air Marshal William Sholto Douglas on 25 November. Douglas set about introducing more squadrons and dispersing the few GL sets to create a carpet effect in the southern counties. Still, in February 1941, there remained only seven squadrons with 87 pilots, under half the required strength. The GL carpet was supported by six GCI sets controlling radar-equipped night-fighters. By the height of 'The Blitz', they were becoming more successful. The number of contacts and combats rose in 1941, from 44 and two in 48 sorties during January 1941, to 204 and 74 during May in 643 sorties. But even in May, 67% of the sorties were visual 'cat’s eye' missions. Curiously, while 43% of the contacts in May 1941 were by visual sightings, they accounted for 61% of the combats. Yet when compared with Luftwaffe daylight operations, there was a sharp decline in German losses to 1%. If a vigilant bomber crew could spot the fighter first, it had a good chance of evading it.

Nevertheless, it was radar that proved to be the critical weapon in the night battles over the UK from this point onward. Dowding had introduced the concept of airborne radar and encouraged its usage, and eventually it became a success. On the night of 22/23 July 1940, Flying Officer Cyril Ashfield (pilot), Pilot Officer Geoffrey Morris (air observer) and Flight Sergeant Reginald Leyland (air tntercept radar operator) of the Fighter Interception Unit became the first crew to intercept and destroy a German aeroplane using onboard radar to guide it to a visual interception, when their AI night-fighter brought down a Dornier Do 17 twin-engined bomber off Sussex. On 19 November 1940 Squadron Leader John Cunningham, who was to become a celebrated night-fighter 'ace', shot down a Junkers Ju 88 twin-enguned bomber using airborne radar, just as Dowding had predicted. By the middle of November, nine squadrons of night-fighters were available, but only one was equipped with the Beaufighter (No. 219 Squadron at RAF Kenley). By 16 February 1941, this figure had grown to 12 squadrons, of which five were equipped, or partially equipped, with the Beaufighter and divided between five fighter groups.

From November 1940 to February 1941, the Luftwaffe shifted its strategy and attacked other industrial cities, especially those of the West Midlands. On the night of 13/14 November, 77 He 111 bombers of the Kampfgeschwader 26 attacked London while 63 similar aircraft of KG 55 struck Birmingham. On the next night, a large force hit Coventry in 'Mondscheinsonate': pathfinder aircraft of the Kampfgruppe 100 led 437 bombers of KG 1, KG 3, KG 26, KG 27, KG 55 and Lehrgeschwader 1, which dropped 350 tons of high explosive, 50 tons of incendiaries and 127 parachute mines, or according to other sources, 449 bombers which dropped 470 tons of bombs. The raid was particularly devastating, and led to widespread use of the phrase 'to coventrate'. More than 10,000 incendiaries were dropped, and of Coventry’s factories 21 were 21 were seriously damaged in Coventry, while loss of public utilities stopped work at nine others, disrupting industrial output for several months. The historic cathedral was all but destroyed together with most of the city centre in the massive firestorm. Only one bomber was lost, in this instance to anti-aircraft fire, despite the fact that the RAF flew 125 night-fighter sorties. No follow-up raids were made, as the Oberkommando der Luftwaffe wholly underestimated the British power of recovery, as indeed RAF Bomber Command would find over Germany from 1943 to 1945. The Germans were surprised by the success of the attack, whose strategic effect was a brief 20% dip in aircraft production.

Five nights later, Birmingham was hit by 369 bombers from KG 54, KG 26, and KG 55. By the end of November, the Germans had 1,100 bombers available to them for night raids, and an average of 200 was available to strike each night. This weight of attack went on for two months, with the Luftwaffe dropping 12,400 tons of bombs. In November 1940, 6,000 sorties and 23 major attacks, each involving the delivery of more than 100 tons of bombs, were flown. Two heavy attacks, each delivering 50 tons of bombs, were also flown. In December, only 11 major and five heavy attacks were made.

Probably the single most devastating attack occurred on the evening of 29 December, when German aircraft attacked the City of London with incendiary and high explosive bombs, causing a firestorm that has been called the Second Great Fire of London. The first group to use these incendiaries was KGr 100, which despatched 10 pathfinder He 111 aircraft that at 18.17 released the first of 10,000 incendiary bombs at a rate which eventually increased to 300 such weapons per minute. In total, 130 German bombers destroyed the historical centre of London. London’s civilian casualties throughout 'The Blitz' amounted to 28,556 persons killed and 25,578 wounded. The Luftwaffe had dropped 16,331 tons of bombs.

Not all of the German bombing effort was made against inland cities, for port cities were also attacked in an effort to disrupt trade and sea communications. In January, Swansea was bombed very heavily on four occasions. On 17 January some 100 bombers dropped a high concentration of incendiaries, some 32,000 in all. The main damage was inflicted on the commercial and domestic areas. Four days later 230 tons were dropped including 60,000 incendiaries. In Portsmouth, Southsea and Gosport waves of 150 bombers destroyed large areas of the towns with 40,000 incendiaries. Warehouses, railway lines and houses were destroyed and damaged, but the docks were largely untouched.During January and February 1941, Luftwaffe serviceability rates declined to the point at which a mere 551 of 1,214 bombers were combat-capable. Seven major and eight heavy attacks were flown, but the weather made it difficult to keep up the pressure. Still, at Southampton, attacks were so effective morale did give way briefly with civilian authorities leading people en masse out of the city.

Although official German air doctrine did target civilian morale, it did not espouse direct attacks on civilians. It hoped instead to destroy civilian morale by destroying factories and public utilities as well as food stocks, the last by attacks on shipping. Nevertheless, Germany’s official opposition to attacks on civilians became an increasingly moot point when large-scale raids were conducted in November and December 1940. Although not encouraged by official policy, the use of mines and incendiaries, for tactical expediency, came close to indiscriminate bombing. Locating targets in skies obscured by industrial haze meant the target area needed to be illuminated and hit 'without regard for the civilian population'. Special units, such as KGr 100, became the Beleuchtergruppen (firelighter groups), which used incendiaries and high explosives to mark the target area. The tactic was expanded into Feuerleitung (blase control) with the creation of Brandbombenfelder (incendiary fields) to mark targets with parachute flares. Bombers carrying 2,205-lb (1000-kg) SC-1000, 3,086-lb (1400-kg) SC-1400 and 3,968-lb (1800-kg) SC-1800 bombs were then dropped to level streets and residential areas. By December, the 5,512-lb (2500-kg) SC-2500 bomb had also come into service.

These decisions, apparently taken at Luftflotte or Fliegerkorps level, meant that attacks on individual targets were gradually replaced by what was, for all intents and purposes, an unrestricted area attack or Terrorangriff (terror attack). Part of the reason for this was inaccuracy of navigation. The effectiveness of British countermeasures against Knickebein caused the Luftwaffe to prefer fire light instead for target marking and navigation. The shift from precision bombing to area attack is indicated in the tactical methods and weapons dropped: KGr 100, for example, increased its use of incendiaries from 13 to 28% and, by December, to 92%. The use of incendiaries, which were inherently inaccurate, indicates that considerably less care was taken to avoid civilian property close to industrial sites. Other units ceased using parachute flares and opted for explosive target markers. Captured German aircrews also indicated that the homes of industrial workers were deliberately targeted.

In 1941, the Luftwaffe shifted strategy once again. Grossadmiral Erich Raeder, commander-in-chief of the Kriegsmarine, had long argued the Luftwaffe should support the U-boat force in the 'Battle of the Atlantic' by attacking shipping in the Atlantic Ocean and bombing British ports. Raeder eventually convinced Hitler of the need to attack British port facilities. Hitler correctly noted that the greatest damage to the British war economy had been done through the destruction of merchant shipping by U-boats and air attacks by small numbers of Focke-Wulf Fw 200 four-engined reconnaissance bombers, and therefore ordered the Luftwaffe to focus its efforts against British convoys. This meant that British coastal centres and shipping at sea to the west of Ireland became the prime targets.

In January 1941, Hitler’s commitment to this revised strategy forced Göring and Jeschonnek to review the air war against the UK, and their agreement to the dictates of Hitler’s Führerweisung Nr 23, issued on 6 February 1941 and giving top priority to the aerial interdiction of British imports by sea. Such a strategy had been recognised before the war, but 'Adlerangriff' and the resulting 'Battle of Britain' had prevented any concentration on striking the UK’s sea communications and thus diverted German air strength to the campaign against the RAF and its supporting structures. The Oberkommando der Luftwaffe had always regarded the interdiction of sea communications to be of less importance than the bombing of land-based aircraft industries.

Compliance with Führerweisung Nr 23 was the only concession made by Göring to the Kriegsmarine over the strategic bombing strategy of the Luftwaffe against the British, and thereafter he would refuse to make available any air units to destroy British dockyards, ports, port facilities, or shipping in dock or at sea lest the Kriegsmarine gain operational if not organisational control of more Luftwaffe units. Raeder’s successor, Admiral (later Grossadmiral) Karl Dönitz, on Hitler’s intervention later gained control of one unit, KG 40, but Göring soon regained it. Göring’s lack of co-operation was detrimental to the single air strategy with a potentially decisive strategic effect on the UK. Instead, he wasted the aircraft of the Fliegerführer 'Atlantik' command on bombing mainland UK rather than attacking convoys. For Göring, whose prestige had been damaged by defeat in the 'Battle of Britain', it was more important to regain this prestige by defeating the UK by air power alone. He was thus always reluctant to co-operate with Raeder.

Even so, the decision by the Oberkommando der Luftwaffe to support the strategy of Führerweisung Nr 23 was instigated by two considerations, both of which had little to do with wanting to destroy the UK’s maritime communications in conjunction with the Kriegsmarine: firstly, the difficulty in estimating the impact of bombing on British war production was becoming apparent, and secondly, the conclusion that British morale was unlikely to break led the Oberkommando der Luftwaffe to adopt the naval option. The indifference displayed by the Oberkommando der Luftweaffe to Führerweisung Nr 23 was perhaps best demonstrated in operational directives which diluted its effect. They emphasised that the core strategic interest was attacking ports but they also insisted on the maintenance of pressure or the diversion of strength onto industries building aircraft, anti-aircraft guns and explosives. Other targets would be considered only if the primary targets could not be attacked because of weather conditions.

Another line in Hitler’s directive stressed the need to inflict the heaviest losses possible, but also to intensify the air war in order to create the impression that an amphibious assault on the UK was planned for 1941. However, meteorological conditions over the UK were unfavourable for flying and prevented any escalation of air operations. The Luftwaffe’s airfields became water-logged and the 18 Kampfgruppen (bomber groups) of the Kampfgeschwadern (bomber wings) were relocated to Germany for rest and re-equipment, and were thus farther removed from possible British targets.

From the German point of view, March 1941 saw an improvement. The Luftwaffe flew 4,000 sorties during that month, these including 12 major and three heavy attacks. The electronic war intensified, but the Luftwaffe flew major inland missions only on moonlit nights. Ports were easier to find and made better targets. To confuse the British, radio silence was observed until the bombs fell. 'X-Gerät' and 'Y-Gerät' beams were placed over false targets and switched to the intended target only at the last minute. Rapid frequency changes were introduced for X-Gerät, whose wider band of frequencies and greater tactical flexibility ensured it remained effective at a time when British selective jamming was degrading the effectiveness of Y-Gerät.

By now, the imminent threat of a German invasion of the UK had all but passed as the Luftwaffe had failed to gain the prerequisite air superiority. The aerial bombing was now principally aimed at the destruction of industrial targets, but also continued with the objective of breaking civilian morale. The attacks were focused against western ports in March. These attacks produced some breaks in morale, with civil leaders fleeing the cities before the offensive reached its height. But the Luftwaffe’s effort eased in the last 10 attacks as seven Kampfgruppen were moved to Austria in preparation for the 'Unternehmen 25' and 'Marita' campaigns in the Balkans against Yugoslavia and Greece. The shortage of bombers caused the Oberkommando der Luftwaffe to improvise. Some 50 Junkers Ju 87 single-engined dive-bombers and Jabos (fighter-bombers) were used, with the official classification leichte Kampfflugzeuge (light bombers) or, on occasion, leichte Kesselringe (light Kesselrings). The defences failed to prevent widespread damage but on some occasions did succeed in preventing German bombers concentrating on their targets. On occasion, only one-third of German bombs hit their targets.

The diversion of the Luftwaffe’s heavier bombers to the new Balkan theatre meant that the crews and units left behind were asked to fly two or three sorties per night. However, the bombers were noisy and cold, and vibrated severely. Added to the tension inherent in the mission, which exhausted and drained crews, tiredness overcame and killed many. In one incident on 28/29 April, a pilot of the KG 30 was flying his 50^th mission when he fell asleep at the controls of his Ju 88 and later woke to discover the entire crew asleep. He roused them, ensured they took oxygen and Dextro-Energen amphetamine tablets, and then completed the mission.

The Luftwaffe was still capable of inflicting much damage, and after the German conquest of western Europe, the air and U-boat offensive against British maritime communications became much more dangerous than the equivalent German offensive during World War I. Liverpool and its port became an important destination for convoys heading through the Western Approaches from North America, bringing supplies and materials, which the considerable railway network distributed to the rest of the country. Air attacks sank 39,126 tons of shipping, with another 111,601 tons damaged. The Minister of Home Security, Herbert Morrison, was also concerned that morale was breaking, noting the defeatism expressed by civilians. Others pointed out that half of the 144 berths in the port had been rendered unusable and cargo unloading capability reduced by 75%. Roads and railways had been blocked and ships could not leave harbour. On 8 May 1941, 57 ships (80,000 tons) had been destroyed, sunk or damaged. Some 66,000 houses had been destroyed and 77,000 people made homeless, with 1,900 people killed and 1,450 seriously hurt during one night. Operations against London up until May 1941 could also have a severe impact on morale. The population of the port of Hull became 'trekkers', people who made a mass exodus from cities before, during and after attacks. The Luftwaffe’s attacks failed to knock out railways or port facilities for long, however, even in the Port of London, which was the target of many attacks. The Port of London, in particular, was an important target, bringing in one-third of overseas trade.

On 13 March, the upper Clyde port of Clydebank near Glasgow was bombed: all but seven of its 12,000 houses were damaged. Many other ports were attacked. Plymouth was attacked five times before the end of the month while Belfast, Hull, and Cardiff were also hit. Cardiff was bombed on three nights, and Portsmouth’s centre was devastated by five raids. The rate of civilian housing loss was averaging 40,000 people per week rendered homeless in September 1940, while in March 1941 two raids on Plymouth and London 'dehoused' 148,000 people. Still, while heavily damaged, British ports continued to support war industry and supplies from North America continued to pass through them while the Royal Navy continued to operate in Plymouth, Southampton and Portsmouth. Plymouth in particular, because of its vulnerable position on the south coast and close proximity to German air bases, was subjected to the heaviest attacks. On 10/11 March, 240 bombers dropped 193 tons of high explosives and 46,000 incendiaries. Many houses and commercial premises were heavily damaged, the city’s electrical supply was knocked out, and five oil tanks and two magazines exploded. Nine days later two waves, of 125 and 170 bombers respectively, dropped heavy bombs, including 160 tons of high explosive and 32,000 incendiaries, destroying much of the city centre. Damage was inflicted on the port installations, but many bombs fell on the city itself. On 17 April 346 tons of explosives and 46,000 incendiaries were dropped from 250 bombers led by the KG 26. The damage was considerable, and the Germans also used aerial mines. Over 2,000 rounds were fired by the anti-aircraft guns, destroying two Ju 88 bombers. By the end of the air campaign over the UK, only 8% of the German effort against British ports was made using mines.

In the north-east of England, major efforts were made against Newcastle upon Tyne and Sunderland. On 9 April 1941, Luftflotte II dropped 150 tons of high explosives and 50,000 incendiaries from 120 bombers in a five-hour attack. Sewer, rail, dockland and electric installations were damaged. In Sunderland on 25 April, Luftflotte II despatched 60 bombers which dropped 80 tons of high explosive and 9,000 incendiaries, causing considerable damage. A further attack on the Clyde river area of Scotland, this time at Greenock, took place on 6 and 7 May. However, as with the attacks in the south, the Germans failed to prevent maritime movements or cripple industry in the regions.

The last major attack on London was flown on 10/11 May 1941, when the Luftwaffe made 571 sorties and dropped 787 tons of bombs. This caused more than 2,000 fires, and 1,436 people were killed and 1,792 seriously injured, which affected morale badly. Another raid was carried out on 11/12 May 1941: Westminster Abbey and the Law Courts were damaged, while the Chamber of the House of Commons was destroyed. One-third of London’s streets were impassable. All but one railway station line was blocked for several weeks. This raid was significant, as 63 German fighters were sent with the bombers, indicating the growing effectiveness of the RAF’s night-fighter defences. German air supremacy at night was also now under threat. British night-fighter operations out over the English Channel were proving successful against bombers which had yet to reach the British coast. This success was not immediately apparent, though. The Blenheim F.Nk I carried four 0.303-in (7.7-mm) machine guns, which lacked the firepower to shoot down a Do 17, Ju 88 or He 111 with any ease. The Blenheim had only a small speed advantage to overtake a German bomber in a stern chase. Added to the fact an interception relied on visual sighting, a kill was most unlikely even in the conditions of a moonlit sky. Despite its poor performance during daylight engagements, the Defiant was a much better night-fighter: it was faster, able to catch the bombers and its configuration of four machine guns in a turret could engage the German bomber from beneath in attacks which offered a larger target, compared to attacks from astern, as well as a better chance of not being seen by the crew and this providing he Germans with less chance to take evasive measures, as well as greater likelihood of detonating the bomber’s payload. In subsequent months a steady number of German bombers would fall to night-fighters.

Improved aircraft designs were in the offing, primarily the Beaufighter, then under development: the type would prove formidable but its development was slow. The Beaufighter had a maximum speed of 320 mph (510 km/h), an operational ceiling of 26,000 ft (7925 m), a climb rate of 2,500 ft (762 m) per minute, and its battery of four 20-mm Hispano cannon and six 0.303-in (7.7-mm) Browning machine guns was much more lethal. On 19 November, in an AI-equipped Beaufighter, Cunningham of the RAF’s No. 604 Squadron shot down a bomber in the first air victory for the airborne radar. In November and December 1940, the Luftwaffe flew 9,000 sorties against British targets and RAF night-fighters claimed only six shot down. In January 1941, RAF Fighter Command flew 486 sorties against 1,965 German sorties, just three and 12 being claimed by the RAF and anti-aircraft defences respectively. In the bad weather of February 1941, RAF Fighter Command flew 568 sorties to counter the Luftwaffe, which flew 1,644 sorties. Night-fighters could claim only four bombers for four losses.

By April and May 1941, the Luftwaffe was still getting through to its targets, taking no more than 1 or 2% losses per mission. On 19/20 April 1941, in honour of Hitler’s 52^nd birthday, 712 bombers hit Plymouth with a record 1,000 tons of bombs, but the British losses were minimal. In the following month, the Germans lost 22 bombers, of which 13 were confirmed to have been shot down by night-fighters. On 3/4 May, nine bombers were shot down in one night. On 10/11 May, London suffered severe damage, but 10 German bombers were downed. In May 1941, RAF night-fighters shot down 38 German bombers. By the end of May, Kesselring’s Luftflotte II had been withdrawn, leaving Sperrle’s Luftflotte III as a token force to maintain the illusion of strategic bombing. Hitler now had his sights set on the invasion of the USSR in 'Barbarossa', and 'The Blitz' came to an end.

Between 20 June 1940, when the first German air operations over the UK began, and 31 March 1941, the Oberkommando der Luftwaffe recorded the loss of 2,265 aircraft over the British Isles, one-fourth of them fighters and one-third of them bombers. At least 3,363 Luftwaffe aircrew were killed, 2,641 missing and 2,117 wounded. Total losses could have been as high as 600 bombers, just 1.5% of the sorties flown. However, a significant number of the aircraft not shot down after the switch to night bombing were wrecked during landings or crashed in bad weather.

The military effectiveness of bombing varied. The Luftwaffe dropped around 40,000 tons of bombs during 'The Blitz', which disrupted production and transport, reduced food supplies, and shook British morale. The bombing also helped to support the U-boat blockade by sinking some 58,000 tons of shipping and damaging 450,000 tons more. Despite the bombing, however, British production rose steadily throughout this period, although there were significant falls during April 1941, probably influenced by the departure of workers for Easter holidays according to the British official history. The British War Production official history noted that the greatest effect on output of warlike stores was on the supply of components and dispersal of production rather than complete equipment.

In aircraft production, the British were denied the opportunity to reach the planned target of 2,500 aircraft per month, which was arguably the bombing’s greatest achievement, as it forced the dispersal of the industry, at first because of damage to aircraft factories and then by a policy of precautionary dispersal. In April 1941, when the targets were British ports, rifle production fell by 25%, filled-shell production by 4.6% and in small-arms production by 4.5%. The strategic impact on industrial cities was varied: most took from 10 to 15 days to recover from heavy raids, although Belfast and Liverpool took longer. The attacks against Birmingham took war industries some three months to recover fully. The exhausted population took three weeks to overcome the effects of an attack.

Thus the German air offensive against the RAF and British industry failed to have the desired effect. More might have been achieved had the Oberkommanso der Luftwaffe exploited the vulnerability of British sea communications. The Allies did so later when RAF Bomber Command attacked rail communications and the US Army Air Forces targeted oil, but that would have required an economic-industrial analysis of which the Luftwaffe was incapable. The Oberkommando der Luftwaffe instead sought clusters of targets that suited the latest policy, which changed all too frequently, and disputes within the leadership were about tactics rather than strategy. Although militarily ineffective, 'The Blitz' cost around 41,000 lives, may have injured another 139,000 people and did enormous damage to British infrastructure and housing stock.

The British began to assess the impact of 'The Blitz' in August 1941 and the Air Staff used the German experience to improve RAF Bomber Command’s offensives. The Air Staff concluded bombers should strike a single target each night and use more incendiaries because they had a greater impact than high explosives on production. It also noted that regional production was severely disrupted when city centres were devastated through the loss of administrative offices, utilities and transport. It believed that the Luftwaffe had failed in precision attack and concluded the German example of area attack using incendiaries was the way forward for operations over Germany.

Some writers claim that the Air Staff ignored a critical lesson, that British morale did not break and that attacking German morale was not sufficient to induce a collapse. Aviation strategists dispute that morale was ever a major consideration for RAF Bomber Command. Throughout the period from 1933 to 1939, none of the 16 Western Air Plans drafted mentioned morale as a target. The first three directives in 1940 did not mention civilian populations or morale in any way. Morale was not mentioned until the ninth wartime directive on 21 September 1940, and the tenth directive in October 1940 mentioned morale by name but industrial cities were only to be targeted if weather prevented raids on oil targets.

The longest-serving commander of RAF Bomber Command in World War II, Air Chief Marshal Sir Arthur Harris, who did see German morale as an objective, did not believe that any collapse of morale could taken place without the destruction of the German economy. The primary goal of RAF Bomber Command was therefore the destruction of the German industrial base and in doing so reduce morale. Late in 1943, just before the 'Battle of Berlin', Harris declared the power of RAF Bomber Command would enable it to achieve 'a state of devastation in which surrender is inevitable'. A summary of Harris' strategic intentions was clear: from 1943 to the end of the war, Harris and other proponents of the area offensive represented the bomber offensive less as an attack on morale than as an assault on the housing, utilities, communications, and other services that supported the war production effort.

A popular image arose of the British population in World War II as a collection of people locked in national solidarity. This image entered the historiography of World War II in the 1980s and 1990s, and was evoked by both the right- and left-wing political factions in British politics in 1982, during the Falklands War, when it was portrayed in a nostalgic narrative in which World War II represented patriotism actively and successfully acting as a defender of democracy. However, raids during 'The Blitz' in fact produced the greatest divisions and morale effects in working-class areas, with lack of sleep, insufficient shelters and inefficiency of warning systems major causes. The loss of sleep was a particular factor, with many not bothering to attend inconvenient shelters. The Communist Party made political capital out of these difficulties. In the wake of the 'Coventry Blitz', there was widespread agitation by the Communist Party over the need for bomb-proof shelters. Many Londoners, in particular, took to using the Underground railway system, without authority, for shelter and sleeping through the night. So worried were the government over the sudden campaign of leaflets and posters distributed by the Communist Party in Coventry and London that the police were sent to seize their production facilities. Up to November 1940, the government was opposed to the centralised organisation of shelter. The Home Secretary, Sir John Anderson, was replaced by Morrison soon afterwards, in the wake of a cabinet reshuffle as the dying Chamberlain resigned. Morrison warned that he could not counter the Communist unrest unless provision of shelters was made. He recognised the right of the public to seize tube stations and authorised plans to improve their condition and expand them by tunnelling. Still, many British citizens, who had been members of the Labour Party, itself inert over the issue, turned to the Communist Party. The Communists attempted to blame the damage and casualties of the Coventry raid on the rich factory owners, big business and landowning interests and called for a negotiated peace. Though they failed to make a large gain in influence, the membership of the party had doubled by June 1941. The 'Communist threat' was deemed important enough for Morrison to order, with the support of the Cabinet, the cessation of activities of the Daily Worker, the Communist newspaper.

The brief success of the Communists also fed into the hands of the British Union of Fascists. Anti-Semitic attitudes became widespread, especially in London. Rumours that Jewish support was underpinning the Communist surge were frequent. Rumours that Jews were inflating prices, were responsible for the Black Market, were the first to panic under attack or were even the cause of the panic, and secured the best shelters via underhanded methods, were also widespread. There was also minor ethnic antagonism between the small Black, Indian and Jewish communities, but despite this these tensions quietly and quickly subsided. In other cities, class divisions became more evident. Over one-quarter of London’s population had left the city by November 1940. Civilians left for more remote areas of the country. Upsurges in population in south Wales and Gloucester intimated where these displaced people went. Other reasons, including industry dispersal may have been a factor. However, resentment of rich self-evacuees or hostile treatment of poor ones were signs of persistence of class resentments although these factors did not appear to threaten social order. The total number of evacuees numbered 1.4 million, including a high proportion from the poorest inner-city families. Reception committees were completely unprepared for the condition of some of the children. Far from displaying the nation’s unity in times of war, the scheme backfired, often aggravating class antagonism and bolstering prejudice about the urban poor. Within four months, 88% of evacuated mothers, 86% of small children and 43% of schoolchildren had been returned home. The lack of bombing in the 'Phoney War' contributed significantly to the return of people to the cities, but class conflict was not eased a year later when evacuation operations had to be put into effect again.