Operation Loge

theatre box

This was the German 76-day bombing campaign against London, the capital of the UK (7 September 1940/10 May 1941).

Known to the British as ‘The Blitz’, this was the major element of the sustained bombing of targets in the UK by the Luftwaffe. By the end of May 1941, more than 43,000 civilians had been killed and more than one million houses destroyed or damaged.

It is worth noting that although the Germans never again achieved the same scale of attack on British targets, they did effect smaller-scale attacks throughout the war, taking the civilian death toll from the bombing to 51,509 persons. In 1944, the development of V-1 ‘flying bomb’ cruise missile and V-2 ballistic missile allowed Germany again to attack London with weapons launched from the European continent, this missile onslaught resulting in another 8,938 British civilians.

Although neither equipped nor trained for the specific task of undertaking an independent strategic air operation, in 1940 Reichsmarschall Hermann Göring’s Luftwaffe was in fact tasked to do so against the UK in the Battle of Britain. From July to September, the Luftwaffe attacked Air Chief Marshal Sir Hugh Dowding’s RAF Fighter Command in a major effort to gain the air superiority that was seen as essential for the launch of the ‘Seelöwe’ invasion of the southern part of the UK. This involved the bombing of convoys in the English Channel and the ports to and from which they were plying, and attacks on RAF fighters and their bases, as well as supporting industries. The Germans believed that the destruction of Fighter Command would give them tactical air superiority over the planned invasion areas, and also that Air Marshal Sir Charles Portal’s (from 5 October Air Marshal Sir Richard Peirse’s) RAF Bomber Command, Air Marshal Sir Frederick Bowhill’s RAF Coastal Command, and the Royal Navy would not be able to operate effectively under conditions of German air superiority to attack and decimate the shipping on which the invasion depended, or to intervene decisively on the land battlefield after the German forces had landed.

As a result of several factors, including Luftwaffe intelligence so poor that often it could not correctly identify and locate even British airfields and aircraft-related industrial facilities, the German attacks on these targets did not yield the results the Germans needed. British fighter aircraft production continued at a rate exceeding that of Germany at times by a factor of 2/1: in overall terms, the British produced 10,000 aircraft in 1940 while the Germans manufactured 8,000. The replacement of pilots and aircrew was more difficult for each side. Thus the RAF and the Luftwaffe each found it difficult to replace their manpower losses, though the Germans had larger reserves of trained men.

The geographical circumstances of the Battle of Britain favoured the British over the Germans: operating over home territory, British pilots could fly again if they survived being shot down, whereas German crews, even if they survived, faced capture; the crews of damaged German aircraft faced a long flight back to their based in occupied France and Belgium, including a crossing of the English Channel; the German heavy fighters and dive-bombers, each with a two-man crew, proved relatively easy pickings for the nimbler British single-seat fighters; and the German medium bombers were each manned by a four- or five-man crew whose loss represented a proportionally greater manpower reduction.

On 7 September the Germans decided to switch their efforts away from the destruction of the RAF’s airfields and support infrastructure as Luftwaffe intelligence suggested that Fighter Command was weakening, and an attack on London would force Fighter Command into a final battle of annihilation while compelling the British government to sure for peace or even surrender.

This decision for a change in strategy is sometimes identified as a major error by the Oberkommando der Luftwaffe: it has been suggested that continued attacks on British airfields might soon have resulted in German air superiority. Others have argued that the Luftwaffe made little impression on Fighter Command in the last week of August and first week of September, and that the shift in strategy was therefore not decisive, and it has also been argued that it was doubtful whether or not the Luftwaffe could have won air superiority before the autumn ‘weather window’ began to close in October. It was also possible that the RAF, had its losses become too severe, could have withdrawn to the north to await ‘Seelöwe’ and then move south once more, refreshed and re-equipped, to held fight off the invasion. Others have averred that the outcome of the air battle was irrelevant given the massive superiority of the British naval forces and the inherent weakness of the German naval forces, which would have made ‘Seelöwe’ a disaster whether or not the Germans possessed air superiority.

At the time, though, Adolf Hitler was greatly frustrated by the Luftwaffe’s inability to produce a decisive result quickly. With no sign of the RAF weakening and the Luftwaffe suffering heavy losses of men and matériel, the Oberkommando der Luftwaffe therefore advocated change of strategy not just in objectives but also in method. This latter was designed to yield a reduction in loss rates, and involved a switch from day to night bombing, so affording the bombers the greater protection offered by darkness.

In the immediate term, however, it was decided to concentrate the daylight bombing on the UK’s industrial cities, with the primary emphasis placed on London. The first major raid of this new effort took place on 7 September. On 15 September, on a date now known to history as Battle of Britain Day, a large-scale raid was launched in daylight, but suffered significant loss for no major result. 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 in order to reduce losses. This became official policy on 7 October, and the new campaign soon started against London and other British cities.

However, the Luftwaffe faced major limitations: while bombers such as the Dornier Do 17, Heinkel He 111 and Junkers Ju 88 were able to fly strategic missions in terms of range, they were medium rather than heavy bombers and could therefore not inflict decisive damaged because of the comparatively light weight of the bomb loads they could deliver to strategic targets.

This deficiency resulted from the decision of Germany’s politico-military leadership, with which the Luftwaffe high command concurred, in the second half of the period between the two world wars to concentrate on the development and procurement of a large force of medium bombers for the tactical- and operational-level roles, rather than a smaller force of heavy bombers for the strategic-level role. This decision can be attributed to several reasons: Hitler did not intend or foresee a war with the UK in 1939; the Oberkommando der Luftwaffe believed a medium bomber could carry out strategic missions; and in the period before the war Germany lacked the matériel resources and technical ability to produce effective four-engined heavy bombers when greater emphasis was placed on the twin-engined medium bomber and single-engined dive-bomber to support the army in the planned offensives of Germany’s new Blitzkrieg concept of fast-moving land warfare. Even so, the Luftwaffe’s medium bomber force was capable of inflicting major damage.

The service’s most significant failings, however, lay not so much in equipment as in its poor intelligence and unclear strategy. So far as the first was concerned, it was not until the spring of 1938 that the Oberkommando der Luftwaffe had been informed that the UK should be considered a possible enemy, and was thus offered little time to gather reliable intelligence on British industries. So far as the second was concerned, the Oberkommando der Luftwaffe failed to decide 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 British import and distribution network, or against targets whose destruction might break the will of the British people to continue their resistance to Germany. Moreover, the German air strategy steadily lost focus during the winter of 1940/41, in which the Oberkommando der Luftwaffe’s senior staff officers argued about tactics rather than strategy.

At the operational level, the German limitations in weapons technology and the speed of the British reactions combined to make it increasingly difficult for the Germans to achieve a strategic result. Successful attacks on British ports, shipping and imports, combined with the disruption of railway traffic in surrounding areas and especially the distribution of coal would have been a positive result for the Germans. However, the use of delayed-action bombs, while initially very effective, gradually had less impact, partly because these weapons often failed to detonate. This was the result of the ingress of moisture, which ruined the bombs’ electrical fuses: Germans estimated a 5 to 10% failure rate, and the British believed that this was in the order of 20%.

Moreover, the British had anticipated the change in strategy and dispersed their production facilities, thereby rendering 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.

It had long been appreciated by the major powers that large urban areas would be difficult to defend against air attack, especially as aircraft technology improved so dramatically during the 1930s, and estimates of the possible casualty rate in a full-scale bombing campaign were revised sharply upward. Convinced that ‘the bomber will always get through’, as opined by current air power theorists and apparently confirmed, at least in popular imagination, by the writings of men such as H. G. Wells and films such as Things to Come, politicians and the civil authorities feared the use of chemical weapons as well as more conventional bombs, and therefore scrambled to organise civil defence within the context of fears of social breakdown, floods of refugees, and hospitals overrun with people suffering from psychological as well as physical injuries.

Despite the wide prevalence of apocalyptic concepts of air bombardment, though, little of practical value was achieved in the creation of ways to protect the vast majority of people who, it was clear, would remain in vulnerable areas. In part, government inaction reflected a continuing hope that war could be avoided or that the retaliatory threat posed by UK’s own bomber force would deter indiscriminate raids. Civil defence was left largely in the hands of local authorities without clear guarantees that their costs could be recouped from the central government. As a result, therefore, some local authorities moved only slowly, so that when war came the supply of shelters was seriously deficient in cities such as Birmingham and Coventry, while in April 1941 Belfast still had spaces for only a quarter of its population. The cost of providing deep bomb-proof shelters capable of sustaining a direct hit was considered prohibitive and there were additional concerns that large communal shelters might become incubators of political disaffection or defeatism. Official policy therefore came to favour dispersed family shelters, constructed by householders in their gardens or, where there were tenements and flats without individual gardens, small brick-built surface shelters. In addition, planning for bombing attacks was based on the premise that these would be of daylight attacks of intense but only short duration. Few, if any, predicted the sustained campaign of night attacks.

And while concerns had been raised in Whitehall about morale in poor areas and especially in the East End, whose large population of Jewish people (in the face of the Nazi threat) and immigrants was ‘likely to form a most unstable element—an element very susceptible to panic’, it was in just such areas that the provision of adequate shelters was most lacking. The most important communal shelters were those in the stations of the London Underground railway system. Although many thousands had used these as shelters during the German air raids of World War I, the British government rejected their use as shelters in 1939, arguing both that unhindered movement of commuters and troops must be guaranteed and that occupants might easily acquire a deep shelter mentality and refuse to leave.

The regularity of the raids, however, made it tempting for increasing numbers of people to enter the tube system and remain there. Minor confrontations occurred, orchestrated in some cases by Communist Party of Great Britain activists, between crowds waiting to go below and London Underground officials whose instructions were to lock the entrances once a raid began. By the second week of heavy bombing, however, the authorities had yielded to popular pressure and orderly queues of people outside the stations became a familiar sight, waiting for 04.00 when they were allowed onto the platforms. Many families regularly sheltered in the tube, others went only in periods of heavy bombing. In mid-September about 150,000 persons slept there every night, with a peak of 177,000 on 27 September, although by the winter and spring months the numbers had declined to 100,000 or less. Especially in the deepest stations, the sound of bomb detonations and anti-aircraft barrages was muffled and rest came easier than above ground; but heavy loss of life resulted from direct hits on several stations such as Marble Arch, Balham, Bank and Liverpool Street.

An approximate census of Londoners in November 1940 placed about 4% in the tube and equivalent large shelters; 9% in public surface shelters, and 27% in domestic Anderson Shelters on house-hold property, usually in back gardens. The unaccounted 60% presumably spent the nights in their homes. In the poorest areas the proportion of people in communal shelters was significantly higher than elsewhere.

By the end of 1940 significant improvements had been made in the London Underground and in many of the more notorious mass shelters. Local authorities distributed heating stoves, washing and sanitary facilities were upgraded, and food services were greatly improved by, for example, regular canteen trains on the tube lines. In time, thousands of tiered bunks were installed in the larger shelters and tickets were issued to regulate the numbers of people and reduce the amount of time spent queuing. In November 1940, at the request of Herbert Morrison, the home secretary, the cabinet also reversed its policy, authorising the construction in the London Underground of deep bomb-proof tunnels capable of accommodating about 80,000 people. Completed after the period of heavy raids, they were never used.

The civilians of London had an enormous role to play in the defence and protection of their city. Many civilians who could not or would not join the military became members of the Home Guard, the Air Raid Precautions (ARP) Service, the Auxiliary Fire Service (AFS), and others. During the Blitz, The Scout Association guided fire engines to where they were most needed, and became known as the ‘Blitz Scouts’. Many unemployed were drafted into the Royal Army Pay Corps and, with others from the Pioneer Corps, were entrusted with salvage and clean-up. The AFS had 138,000 personnel by July 1939 whereas, only one year earlier, it had numbered just 6,600 full-time and 13,800 part-time fireman in the entire country.

The Women’s Voluntary Services for Civil Defence (WVS) was set up under the direction of Sir Samuel Hoare, home secretary in 1938, specifically to provide several types of aid in the event of air raids, and in this capacity Hoare considered the WVS as the female branch of the ARP. The WVS organised the ‘Pied Piper’ evacuation of children, established centres for those displaced by bombing, operated canteens, salvage and recycling schemes. By the end of 1941, it had 1 million members.

Before the outbreak of war, civilians had been issued with 50 million respirators (gas masks).

In the inter-war years and after 1940, Dowding, as commander of Fighter Command, has received credit for the defence of British air space and the failure of the Luftwaffe to achieve air superiority. Dowding had devoted so much of his effort in preparing and readying day fighter defences, however, there was little to prevent the Germans carrying out an alternative strategy of bombing by night. It should ben borne in mind, however, that in the absence of an effective and comparatively light airborne interception radar, effective night fighter defence was an all but impossible task.

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 he was responsible for the day and night defence of the UK, and also that the blame for failure would rightly be laid at his door. When urgent improvements and changes were required, Dowding appeared reluctant to act quickly. The Air Staff felt that this reflected his stubborn nature and reluctance to co-operate. Dowding’s opponents in the Air Ministry, already somewhat critical of his handing of the day battle, were ready exploit these failings to attack him. Dowding was summoned to an Air Ministry conference on 17 October 1940 to explain the poor state of night defences and the supposed failure of what was in fact his ultimately successful day strategy. The criticism of his leadership extended far beyond the Air Council, and the Minister of Aircraft Production, Lord Beaverbrook, and Prime Minister Winston Churchill themselves intimated that their support was waning.

While the failure of night defence preparations was undeniable, it should have been borne in mind that it was not Dowding’s responsibility to accrue resources. The general neglect of the RAF until the late spurt of rearmament in 1938 had left sparse resources to build defences. While it was permissible to disagree with Dowding’s operational and tactical deployment of forces, the failure of both the government and the Air Ministry to allot resources was ultimately the responsibility of the civil and military institutions at large.

In the pre-war period, the national government of Prime Minister Neville Chamberlain had stated that night defence should not consume much of the national effort and, along with the Air Ministry, did not make it a priority. The attitude of the Air Ministry flew in the face of the experiences of World War I, when the operations of a very modest number of German bombers had caused physical and psychological damage out of all proportion to the resources deployed. Some 250 tons of bombs had been dropped, killing 1,413 people and injuring 3,500 more. In 1917/18 the German raids had been scaled down in face of countermeasures which demonstrated defence against night air raids was possible.

Although night air defence was causing greater concern as the seeming inevitability of war approached, it was still not at the forefront of RAF planning, which was concentrated very largely on planning daylight fighter defences. The difficulty which RAF bombers had in navigation by night led the British to believe that German bombers would encounter the same problem, and thus be unable to reach and identify their targets.

Moreover, British air doctrine had stressed, since the time of Marshal of the RAF Sir Hugh Trenchard as Chief of the Air Staff in the 1920s, that offence was the best means of defence. British defensive strategy actually revolved around offensive action, what became known as the cult of the offensive. To prevent German formations from hitting targets in the UK, RAF Bomber Command would destroy the French (later revised to German) forces on their own bases, aircraft in their factories, and fuel reserves by attacking oil facilities. This philosophy was in fact wholly impractical as Bomber Command was not equipped for the task at that time and would not be for some years. Even so, this strategy retarded the development of fighter defences in the 1930s.

Dowding agreed that air defence would require some offensive action, and fighters alone could not defend the UK. At the start of the war in September 1939, and for the 12 months that followed, the RAF lacked specialised night fighting aircraft, and relied on anti-aircraft units which were poorly equipped and lacking in numbers.

Meanwhile the Luftwaffe had developed radio navigation devices to overcome the need for training in celestial navigation, and came to rely on three major systems: Knickebein (crooked leg), X-Gerät (X-Device) and Y-Gerät (Y-Device). This led the British to develop countermeasures, giving rise to the ‘Battle of the Beams’. Bomber crews already had some experience with these types of systems as a result of the adoption of the Lorenz beam, a blind-landing aid which allowed aircraft to land at night or in bad weather. But the Lorenz system could only be used over short ranges, so the Germans turned to the Knickebein aid, a system using much stronger signal transmissions. The system was conceptually simple: two transmitter antennae were trained in azimuth so that their beams crossed at a point directly above the target; the German bombers then flew along either beam until they started to pick up the signal from the other beam; and when a continuous tone was heard from the second beam the crew knew they were above the target and began dropping their bombs.

While Knickebein could be used by all the bombers fitted with the right receiver equipment, the higher-frequency X-Gerät could be used only by specially trained crews. Special receivers were mounted in He 111 bombers, which could be identified by the additional radio mast on the fuselage: ground-based transmitters sent pulses at a rate of 180 per minute; the X-Gerät received and analysed the pulses, giving the pilot both visual and aural ‘on course’ signals; three beams intersected the beam along the He 111’s flight path, the first acting as a warning for the bomb-aimer to start the bombing clock which he would activate only when the second cross-beam was reached; when the third cross-beam was reached the bomb-aimer activated a third trigger, which stopped the first hand of the equipment’s clock, with the second hand continuing. When the second hand realigned with the first, the bombs were released. The clock’s timing mechanism was co-ordinated with the distances of the intersecting beams from the target so the target was directly below when the bomb release occurred.

The Y-Gerät was the most complex of the three systems: it was, in effect, an automatic beam-tracking system, operated through the bomber’s autopilot; the single approach beam along which the bomber flew was monitored by a ground controller using signals from the station retransmitted by the bomber’s equipment; in this way the distance the bomber travelled along the beam could be precisely verified; direction-finding checks also enabled the controller to keep the crew on an exact course; the crew would finally be instructed to drop their bombs either by issue of a code word from the ground controller, or at the ending of the transmitted signal. Although its maximum usable range was similar to the previous systems, it was very accurate and it was not unknown for specific buildings to be hit.

In June 1940 a German prisoner of war was overheard talking about the Knickebein system, and the details of the conversation were passed to an RAF Air Staff technical advisor, Dr R. V. Jones. The British started an in-depth investigation which confirmed to Jones that this was no mere blind-landing device. Jones began a search for the German beams. Avro Anson aircraft of the Beam Approach Training Development Unit (BATDU) were flown up and down the UK fitted with a 30-MHz receiver to detect them. Soon a beam was traced to Derby (which had been mentioned in Luftwaffe transmissions).

The first jamming operations were carried out using simple hospital x-ray machines: a subtle form of distortion was introduced, up to nine special transmitters directing their signals at the beams in a manner that widened its path, negating its ability to fix targets accurately. Confidence in the device was diminished by the time the Luftwaffe decided to launch large-scale raids.

The counter operations were carried out by electronic counter-measures units of No. 80 Wing under Wing Commander Edward Addison. The production of false radio navigation signals by retransmitting the originals was a technique known as masking beacons (meacons). 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 signals 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 the stronger signal on the direction finder; the reverse would apply only if the meacon were 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, these being good enough to stand up to skilled observation, and a sizeable weight of German bombs fell on these diversionary 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 simulate heavy industrial targets. In those sites, carbon arc lamps were used to create the flash of tram cables. 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 used carefully. The fake fires could only begin when the bombing started over an adjacent target and its effects were brought under control. If they were too early the chances of success receded, and if they were too late 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 being similar to those of the German 551-lb (250-kg) C-250 and 1,102-lb (500-kg) C-500 Flammbomben. The hope was that if it could deceive the leading German bomb-aimers, it would draw more bombers away from the real target.

The first planned air raids on London were directed mainly at the Port of London, causing severe damage, and began late in the afternoon of 7 September within ‘Loge’ against London and ‘Seeschlange’ against other British industrial cities.

‘Loge’ continued for 57 nights, and in the first attack the Germans used 348 bombers and 617 fighters. The change in German strategy at first caught the RAF off-guard, and extensive damage and civilian casualties resulted. Some 107,400 tons of shipping was damaged in the Thames river estuary and of some 1,600 civilian casualties included about 400 persons killed. The Luftwaffe lost 41 aircraft (14 bombers, 16 single-engined fighters, seven twin-engined fighters and four reconnaissance aircraft), while Fighter Command lost 23 fighters, with six pilots killed and another seven wounded. Altogether, 247 bombers of Generalfeldmarschall Hugo Sperrle’s Luftflotte III attacked on that night.

On 8 September the Luftwaffe returned, and in this raid 412 people were killed and 747 severely wounded. On the following day the Oberkommando der Luftwaffe gave the appearance of 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 flying conditions were poor, heavy raids took place that afternoon on the London suburbs and the airfield at Farnborough. The day’s fighting cost Generalfeldmarschall Albert Kesselring’s Luftflotte II some 24 aircraft including 13 single-engined fighters, while Fighter Command lost 17 fighters and six pilots.

Over the few days which followed, the weather was poor, so the next major effort had to wait until 15 September 1940. On this day the Luftwaffe made two large daylight attacks on London along the Thames river estuary, targeting the docks and rail communications in the city. The German hope was both to destroy these targets and to draw the RAF into defending them, allowing the Luftwaffe to destroy the British fighters in large numbers and thereby gain air superiority. Large-scale air battles broke out and lasted most of the day. The first attack merely damaged the rail network for three days, and the second attack failed altogether. The air battle later became commemorated as Battle of Britain Day. The Luftwaffe lost 18% of the bombers sent on the day’s operations, and failed to gain air superiority.

While Göring remained optimistic that the Luftwaffe could prevail, Hitler was not so sanguine and on 17 September postponed ‘Seelöwe’ rather than gamble Germany’s newly gained military prestige on a risky operation to make an amphibious assault across the English Channel.

In the last days of the Battle of Britain, 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 the opportunity it needed to switch to night attacks on 7 October.

On 14 October, the heaviest night attack to date saw 380 of Luftflotte III’s bombers attack London in a raid which killed about 200 people and injured another 2,000. The guns of General Sir Frederick Pile’s Anti-Aircraft Command fired 8,326 rounds but destroyed only two bombers. On 15 October the bombers returned and started some 900 fires as a result of dropping a mix of 376 tons of high explosive and 10 tons of incendiaries. Five main rail lines were cut and a considerable quantity of rolling stock was damaged.

‘Loge’ continued during October. According to German sources, 9,000 tons of bombs (10% by day) were dropped in that month, and more than 5,400 tons were was aimed at London during the night. Birmingham and Coventry were the recipients of 450 tons in the last 10 days of October, Liverpool received 180 tons, Hull and Glasgow were attacked, and 730 tons were spread out all over the UK. Little tonnage was dropped on Fighter Command airfields as Bomber Command’s airfields were now a higher priority.

The German policy at this time was firstly to continue progressive attacks on London, chiefly by night; secondly to interfere with production in the vast industrial arms factories of the West Midlands, again chiefly by night attack; and thirdly to disrupt factory production by daylight fighter-bomber attacks. Kesselring’s Luftflotte II was instructed to despatch 50 sorties per night against London and attack eastern harbours in daylight, while Sperrle was ordered to dispatch 250 sorties per night including 100 against the West Midlands.

‘Seeschlange’ would be carried out by General Hans Geisler’s X Fliegerkorps of Generaloberst Hans-Jürgen Stumpff’s Norway-based Luftflotte V, which concentrated its efforts on mining operations against shipping but also took part in the bombing of land targets. By 19/20 April 1941 the X Fliegerkorps had dropped 3,984 mines, one-thirds of the total dropped. The mines’ ability to destroy entire streets earned them great fear in the UK, but several of these devastating weapon fell unexploded into British hands, and this paved the way for the rapid development of countermeasures which damaged the German anti-shipping campaign.

By mid-November 1940, when the Germans adopted a revised plan, more than 12,000 tons of high explosive and nearly 1 million incendiaries had fallen on London. Outside the 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. The docks and railway communications of London had taken a severe beating, and much damage had been inflicted on the railway system outside the British 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 as a result of the threat posed by delayed-action bombs. But the great bulk of the traffic went on.

Observers of the Ministry of Home Security failed to discover the slightest sign of a break in morale despite the destruction of life and property. More than 13,000 civilians had been killed, and nearly 20,000 injured, in September and October alone.

The British night air defences were still ineffective. Few 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 anti-aircraft guns were deployed in the whole of the UK. Of the heavy weapons, some 200 were of the obsolescent 3-in (76-mm) type, and the rest were more useful 3.7- and 4.5-in (94- and 114-mm) weapons with a theoretical ceiling of more than 30,000 ft (9145 m) but a practical ceiling of 25,000 ft (7620 m) as the predictor used with them could not accept the input of greater altitudes. The light guns, of which about half were of the excellent 40-mm Bofors type, tackled aircraft up to an altitude of 6,000 ft (1830 m). Although the guns improved civilian morale, it is now believed that fragments of the anti-aircraft guns’s shells achieved little against the German bombers and in fact caused British casualties on the ground.

There were still only a few fighter aircraft which were able to operate at night, ground-based radar was limited, airborne radar was ineffective and RAF night fighters were for all intents and purposes useless. RAF day fighters were converting to night operations, and the inadequate Bristol Blenheim night-fighter was being replaced by the powerful Bristol Beaufighter, but this latter was available only in very small numbers.

By the second month of the Blitz, however, the British defences were not proving successful. Therefore London’s defences were rapidly reorganised by Pile, but the difference this made to the air defence’s capability was questionable. With 2,631 weapons available, the British were still 33% below establishment in heavy anti-aircraft guns.

Dowding had to rely on night fighters, and in the 1940/41 period the most successful of these was the Boulton Paul Defiant turret fighter, which equipped four squadrons and shot down more German aircraft than any other type of fighter.

But the anti-aircraft gun position improved over several months as more effective use was made of radar and searchlights: from 20,000 shells spent per raider shot down in September 1940, the figure improved to 4,087 in January 1941 and to 2,963 in February.

Airborne interception radar was still unreliable, though. The heavy fighting in the Battle of Britain had consumed most of Fighter Command’s resources, so there had been little investment in the development of a night fighting capability. Out of desperation rather than any belief that the concept would prove useful, bombers were flown with airborne searchlights, but to little avail. Of greater potential was the GL (Gunlaying) radar and searchlights with fighter direction from RAF fighter control rooms to begin the creation of a GCI (Ground-Controlled Interception) system under control of the RAF’s Nos 10, 11 and 12 Groups.

Whitehall’s disquiet at the failures of the RAF led to the replacement of Dowding, who was already due for retirement, by Air Marshal Sir William Sholto Douglas on 25 November. Douglas set about introducing more squadrons and dispersing the few GL sets to create a effective carpet covering the the southern counties of the UK. Still, in February 1941, there remained only seven night-fighter 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, the night fighters were finally starting to become successful. The number of contacts and resulting combats rose in 1941, from 44 and two in 48 sorties during January 1941, to 204 and 74 in 643 sorties during May. But even in May, 67% of the sorties were visual missions. Curiously, while 43% of the contacts in May 1941 were by visual sightings, they accounted for 61% of the combats.

Yet by comparison with Luftwaffe daylight operations, there was a sharp decline in German loses to 1%. If vigilant crew could spot the night fighter first, it had a good chance of evading the fighter. Nevertheless, it was radar which proved to be critical weapon in the night battles over the UK from this time onward.

Dowding had introduced the concept of airborne radar and encouraged its usage. Eventually it would become a success. On the night of 22/23 July 1940, a night fighter of the Fighter Interception Unit had become the first AI-equipped aeroplane to intercept and destroy a German aeroplane using onboard radar to guide its crew to a visual interception of a Do 17 off Sussex. By mid-November nine squadrons were available, but of these only one was equipped with the Beaufighter. By 16 February 1941 this figure had grown to 12 squadrons of which five were equipped or partially equipped with the Beaufighter, spread over five groups.

From November 1940 to February 1941 the Germans changed their strategy and attacked industrial cities, largely in the West Midlands, although London also remained a priority target. On the night of 13/14 November, 77 He 111 bombers of Oberst Alexander Holle’s Kampfgeschwader 26 attacked London while 63 bombers of Oberstleutnant Hans Korte’s KG 55 bombed Birmingham. On the following night a large bomber force assaulted Coventry in ‘Mondscheinsonate’. Pathfinder aircraft of Major Heinrich Pusch’s (from 22 November Major Joachim Stollbrock’s) Kampfgruppe 100 led 437 bombers of Oberst Karl Angerstein’s KG 1, Oberst Wolfgang von Chamier-Glisczinski’s KG 3, Holle’s KG 26, Major Gerhard Ulbricht’s KG 27, Korte’s KG 55 and Oberst Friedrich Karl Knust’s Lehrgeschwader 1, which dropped 357 tons of HE bombs, 51 tons of incendiaries and 127 parachute mines, though other sources say 449 bombers and a total of 480 tons of bombs. The raid was particularly devastating, largely as a result of the dropping of more than 10,000 incendiaries that started major sires. About 21 factories were seriously damaged, and the loss of public utilities stopped work at another nine, disrupting industrial output for several months. The only bomber lost was to anti-aircraft fire, despite the RAF flying 125 night sorties. No follow-up raids were made as the Oberkommando der Wehrmacht overestimated the British power of recovery. The Germans were surprised by the success of the attack, but the concentration had been achieved largely by accident. The strategic effect of the raid was a brief 20% dip in aircraft production.

Five nights later Birmingham was hit in ‘Regenschirm’ by 369 bombers of Holle’s KG 26, Oberstleutnant Otto Höhne’s KG 54 and Korte’s KG 55.

By the end of November, 1,100 bombers were available for night raids, with an average of 200 able to strike per night. This weight of attack went on for two months, with the Luftwaffe dropping 12,600 tons of bombs. In November 1940, 6,000 sorties and 23 major attacks, in each of which more than 100 tons of bombs were dropped, were flown. Two heavy attacks were also flown to drop 45 tons of bombs.

In December, only 11 major and five heavy attacks were made. Probably the single most devastating attack took place during the evening of 29 December, when the bombers attacked the City of London with incendiary and high explosive bombs, causing a firestorm. The first group to use the incendiaries was KGr 100 which despatched 10 He 111 pathfinder machines. At 18.17 these aircraft released the first of 10,000 incendiaries at a rate which soon rose to 300 per minute. A total of 130 bombers destroyed the historical centre of London.

Civilian casualties in London throughout the Blitz amounted to 28,556 killed and 25,578 wounded resulting from the delivery of 16,593 tons of bombs.

Not all of the Luftwaffe’s campaign was waged against inland cities. 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 about 100 bombers dropped a high concentration of incendiaries, some 32,000 in all, and the main damage was inflicted on the commercial and domestic areas. Four days later 230 tons was dropped including 60,000 incendiaries.

In Portsmouth, Southsea and Gosport waves of 150 bombers destroyed major parts of the city with 40,000 incendiaries. Warehouses, rail lines and houses were destroyed and damaged, but the docks were largely untouched.

In January and February 1941 the Luftwaffe’s serviceability rates declined, until just 551 of 1,214 bombers were combat worthy. Seven major and eight heavy attacks were flown, but the weather made it difficult for the Germans to maintain the pressure. Although German official air doctrine did consider civilian morale a valid target, it did not espouse direct attacks on the civilian population but instead hoped to break morale by destroying factories and public utilities as well as food stocks, the last by attacks on shipping and its facilities. Nevertheless, its 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 they needed to be illuminated ‘without regard for the civilian population’.

Special units such as the KGr 100 became the Beleuchtergruppe (firelighter group), which used incendiaries and HE bombs to mark the target area. The tactic was expanded into Feuerleitung (blaze control) with the creation of Brandbombfelde (incendiary fields) to mark targets. These were marked out by parachute flares. Then bombers carrying 2,205-lb (1000-kg) SC 1000, 3,086-lb (1400-kg) SC 1400 and 3,968-lb (1800-kg) and SC 1800 Satan bombs were used to level streets and residential areas. By December the 5,511-lb (2500-kg) SC 2500 Max bomb was being used.

These decisions, apparently taken at the Luftflotte or Fliegerkorps level, meant 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 the generally poor standard of navigational accuracy.

The effectiveness of British countermeasures against Knickebein, which was designed to avoid the need for area attacks, forced the Luftwaffe to resort to these methods. The shift from precision bombing to area attack is indicated in the tactical methods and weapons dropped. The KGr 100 increased its use of incendiaries initially from 13 to 28%, but by December this had increased to 92%. The use of inherently inaccurate incendiaries indicated that much less care was being taken to avoid civilian property located close to industrial sites. Other units ceased using parachute flares and opted for explosive target markers. Captured German air crews also indicated the homes of industrial workers were deliberately targeted.

Early in 1941 the Luftwaffe changed 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 and striking at 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 effected by the U-boat arm and air attacks by small numbers of Focke-Wulf Fw 200 Condor long-range maritime reconnaissance bombers. He now ordered that attacks be carried out on those targets which were also the target of the Kriegsmarine. This meant that British coastal centres and shipping at sea in the areas to the west of Ireland became prime targets.

Hitler’s interest in this strategy forced Göring and Generaloberst Hans Jeschonnek, the Oberkommando der Luftwaffe’s chief-of-staff, to review the progress of their air war against the UK in January 1941. This led the two men into agreement with Hitler’s Führerweisung Nr 23 issued on 6 February 1941 and giving maximum priority to the aerial interdiction of British sea imports. This strategy had been recognised before the war, but the Battle of Britain and the first stages of ‘Loge’ had prevented the implementation of air attacks on the British sea communications and diverted German air strength to the campaign against the RAF and its supporting structures.

His response to Führerweisung Nr 23 was the only concession made by Göring to the Kriegsmarine over the strategic bombing strategy of the Luftwaffe against the UK, and thereafter he refused to make available any air units for the specific task of destroying British dockyards, ports, port facilities and shipping in dock or at sea, lest the Kriegsmarine gain control of more Luftwaffe units. Raeder’s successor, Grossadmiral Karl Dönitz, on Hitler’s direct intervention, later gained control of one unit, the specialist KG 40, but Göring soon regained it. Göring’s lack of co-operation was detrimental to the one air strategy with potentially decisive strategic effect on the UK. Instead, he wasted aircraft of the Fliegerführer 'Atlantik' command on bombing the British mainland rather than attacking convoys.

Even so, the Oberkommando der Luftwaffe’s decision to support the strategy laid out in the Führerweisung Nr 23 was instigated by two considerations, both of which had little to do with any desire to destroy British sea communications in conjunction with the Kriegsmarine. First, the difficulty in estimating the impact of bombing upon war production was becoming apparent, and second, the conclusion British morale was unlikely to break led Oberkommando der Luftwaffe to adopt the naval option. The indifference displayed by Oberkommando der Luftwaffe to the Führerweisung Nr 23 was perhaps best demonstrated in operational directives which diluted its effect. These directives emphasised that the Luftwaffe’s core strategic interest was attacking ports but also insisted in maintaining pressure, or diverting strength, onto industries building aircraft, anti-aircraft guns, and explosives. Other targets would be considered if the primary ones could not be attacked because of weather conditions.

Another element of the directive stressed the need to inflict the heaviest possible losses, but also to intensify the air war in order to create the impression an amphibious assault on the UK was planned for 1941. Weather conditions over the UK were not favourable for flying, however, and thereby prevented any escalation of the current air operations. Airfields became water-logged and the 18 Kampfgruppen of the Luftwaffe’s Kampfgeschwadern were relocated to Germany for rest and re-equipment.

From the German point of view, March 1941 saw an improvement. The Luftwaffe flew 4,000 sorties, including 12 major and three heavy attacks, during the month. 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 real 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 threat of imminent invasion had all but passed with the Luftwaffe’s failure to gain the prerequisite of air superiority. The bombing was now principally aimed at the destruction of industrial targets, but also continued with the objective of breaking the morale of the civilian population. The attacks were focused against western ports in March. These attacks produced some breaks in morale, but the Luftwaffe’s effort eased in the last 10 attacks as seven Kampfgruppen were moved to Austria in preparation for ‘Unternehmen 25’ and ‘Marita’ against Yugoslavia and Greece respectively. The shortage of bombers caused the Oberkommando der Luftwaffe to improvise. Some 50 Junkers Ju 87 dive-bombers and Jabos (Jagdbombern or fighter-bombers) were officially reclassified as leichte Kampfflugzeuge (light bombers).

The defences were still incapable of preventing the German infliction of widespread damage, but on some occasions did prevent the German bombers from concentrating on their targets. Occasionally, only 33% of the German bombs landed on their designated targets. The lack of heavier bombers, resulting from their diversion to the Balkans, also meant the crews and units left behind were asked to fly two or three sorties per night. The bombers were noisy, cold and vibrated badly. Added to the tension of the missions, which exhausted and drained crews, exhaustion caught up with all and killed many. Even so, the Luftwaffe was still capable of inflicting major damage.

With the German occupation of much of western Europe, the British rightly feared and indeed expected an intensification of U-boat and air attack on their sea communications from bases in Norway and France. Such an event would have serious consequences on the future course of the war should the Germans succeed. Liverpool and its port replaced more southern cities and ports as the primary terminus for convoys heading through the Western Approaches from North America with supplies and matériel which were then distributed to the rest of the country by the British railway network. Operations against Liverpool were successful. Around 75% of the port’s capacity were lost in one period, and it lost 39,126 tons of shipping to air attacks, with another 111,601 tons damaged.

Morrison was also worried morale was breaking, noting the defeatism expressed by civilians. Other sources point to half of the 144 berths rendered unusable, while cargo unloading capability was reduced by 75%. The roads and railways were blocked and ships could not leave harbour. On 8 May 1941, 57 ships (81,000 tons) were destroyed, sunk or damaged. About 66,000 houses were destroyed, 77,000 people made homeless, and 1,900 people killed and 1,450 seriously hurt in one night.

Operations against London up to May 1941 could also have exercised a severe impact on British civilian morale. The people of the port of Hull became ‘trekkers’, a term used to describe the mass exodus of people from cities before, during and after attacks. However, the attacks failed to knock out or damage railways or port facilities for long, this including even the Port of London, which had been the target of many attacks. The Port of London in particular was a target of strategic significance, for through it passed 33% of British overseas trade.

On 13 March, Clydebank port near Glasgow was bombed. All but seven of its 12,000 houses were damaged. Many more ports were attacked. Plymouth was attacked five times before the end of the month, and Belfast, Hull and Cardiff were also hit. Cardiff was bombed on three nights, and Portsmouth city centre was devastated by five raids.

The rate of civilian houses lost was averaging 40,000 per week in September 1940. In March 1941, two raids on Plymouth and London accounted for 148,000. While heavily damaged, however, British ports continued to support war industry, and supplies from North America continued to pass through them. The Royal Navy continued to operate in Plymouth, Southampton and Portsmouth. Plymouth in particular, because of its vulnerable position on the south coast and this its close proximity to German air bases in north-western France, 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 centres were heavily damaged, the electrical supply was knocked out and five oil tanks and two magazines exploded. Nine days later, two waves of 125 and 170 bombers dropped heavy bombs, including 160 tons of high explosive and 32,000 incendiaries. Much of the city centre was destroyed. 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. The anti-aircraft guns fired more than 2,000 rounds, destroying just two Ju 88 bombers.

By the end of the air campaign against the UK, only 8% of the German effort against British ports was made using mines.

In the north, substantial efforts were made against the large port cities of Newcastle-upon-Tyne and Sunderland. On 9 April Luftflotte II dropped 150 tons of bombs and 50,000 incendiaries from 120 bombers in a five-hour attack. Sewer, rail, docklands, and electric installations were damaged. Against Sunderland on 25 April, Luftflotte II despatched 60 bombers, which dropped 80 tons of bombs and 9,000 incendiaries. Much damage was done. However, as with the attacks in the south, the Germans failed did not prevent maritime movements or cripple industry in the regions.

The last major attack on London took place on 10/11 May, on which the Luftwaffe flew 571 sorties and dropped 787 tons of bombs. This caused more than 2,000 fires and affected morale badly. Another but smaller raid followed on 11/12 May. Some 1,436 people were killed and 1,792 seriously injured. Westminster Abbey and the Law Courts were damaged, and a 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 also significant as 63 German fighters were sent with the bombers, this indicating the German reaction to the growing effectiveness of the British night fighter defences, which now posed a threat to the German air supremacy at night. British night fighter operations out over the English Channel were also proving highly successful, though this was not immediately apparent as many German losses were not spotted as they fell into the water.

The Blenheim F.Mk I was undergunned, with just four 0.303-in (7.7-mm) machine guns with which it was difficult to knock the Do 17, He 111 and Ju 88. Moreover, the Blenheim struggled to reach the speed of the German bombers. Added to the fact an interception relied on visual sighting, a kill was most elusive even in the conditions of a moonlit sky. The Defiant NF.Mk I and radar-equipped NF.Mk IA were much better aircraft in the night-fighter role. They were faster and able to catch the bombers, and its armament configuration was also beneficial: the location of its armament (still four rifle-calibre machine guns) in a turret instead of a fixed forward-firing installation allowed it to engage an unsuspecting bomber from beneath or alongside.

In subsequent months a steadily increasing number of German bombers fell to night fighter attack. Better news was in the offing with the radar-equipped Beaufighter, whose development was slow but which offered good performance and also the more potent firepower of four 20-mm cannon and six 0.303-in (7.7-mm) machine guns.

In November and December 1940 the Luftwaffe flew 9,000 sorties against British targets, and RAF night fighters claimed to have shot down only six aircraft. In January 1941 Fighter Command flew 486 sorties against 1,965 made by the Germans, just three and 12 of which were claimed by the RAF and anti-aircraft defences respectively. In the bad weather of February 1941, Fighter Command flew 568 sorties to counter the Luftwaffe, which flew 1,644 individual sorties, and the night fighters claimed only four bombers for the loss of four of their own number.

By April and May 1941 the Luftwaffe’s bombers was still getting through to their targets, taking no more than 1 or 2% losses on any given mission. On 19/20 April, 712 bombers hit Plymouth with a record 1,000 tons of bombs, their losses being minimal. In the following month, 22 German bombers were lost with 13 confirmed to have been shot down by night fighters. On 3/4 May, nine were shot down in one night. On 10/11 May, London suffered severe damage, but 10 German bombers were downed. In May RAF night fighters shot down 38 German bombers.

By the end of May Luftflotte II had been withdrawn for redeployment to the east in preparation for ‘Barbarossa’, leaving Luftflotte III as a token force to maintain what was by now only the illusion of strategic bombing. With Hitler’s sights now set on the ‘Barbarossa’ invasion of the USSR, the Blitz drew toward its end.

Between 20 June 1940, when the very first German air operations began over the UK, and 31 March 1941, the Oberkommando der Luftwaffe recorded the loss of 2,265 German aircraft over the British Isles. A quarter of these were fighters, and one-third were bombers. No fewer than 3,363 Luftwaffe airmen had been killed, 2,641 were missing and 2,117 wounded. Total losses were in the order of 600 bombers, just 1.5% of the sorties flown. A sizeable proportion were wrecked in landings or in bad weather.

The military effectiveness of the German bombing varied considerably. The Luftwaffe dropped about 41,000 tons of bombs during the Blitz, disrupting production and transport, reducing food supplies, and shaking British morale. It also helped to support the U-boat blockade by sinking some 58,000 tons of shipping and damaging 450,000 tons. In overall terms, 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. The British official history on war production noted that the greater impact was upon the supply of components rather than on 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 greatest achievement of the German bombing, as it forced the dispersal of industry. In April 1941, when the targets were British ports, rifle production fell by 25%, filled-shell production by 4.6%, and small arms production by 4.5%. The strategic effect against industrial cities was varied. Most cities took between 10 and 15 days to recover from heavy raids, though Belfast and Liverpool took longer, and Birmingham needed three months. An increasingly exhausted population took three weeks to overcome the effects of an attack.

The air offensives against the RAF and British industry both failed to have the effect desired. More might have been achieved had the Oberkommando der Luftwaffe had seen and decided to exploit any British weak spots, in particular the vulnerability of British maritime communications. Instead the Oberkommando der Luftwaffe sought clusters of targets which suited the latest of an often-changed strategies.

Militarily ineffective as it ultimately proved, the Blitz nonetheless caused enormous damage to the UK’s infrastructure and housing stock. It cost around 41,000 lives, while figures for the wounded may have been as high as 139,000.

The relieved British began to assess the impact of the Blitz in August 1941, and the Air Staff used the lessons to improve Bomber Command’s now-growing offensive. The Air Staff concluded that bombers should strike a single target each night and use more incendiaries because they had a greater impact than high explosive bombs on production. The Air Staff also noted that regional production was severely disrupted when city centres were devastated through the loss of administrative offices, utilities and transport. The Air Staff also came to believe that the Luftwaffe had failed in the delivery of precision attacks, and concluded the German concept of area attack using incendiaries was the way forward for British operations over Germany.