These last raids produced very heavy damage to the centre of the city, and in the case of Barmen, attacked on the night of 29–30 May by 719 bombers, created a major conflagration that consumed four-fifths of the built-up area and killed 3,400 people, the largest number in any one raid until then. Wuppertal, the other half of the town of Wuppertal-Barmen, was raided on 24–25 June by 630 aircraft and 94 per cent of its urban area was destroyed or damaged, with 1,800 deaths. In the four months of the heavy ‘crash raids’, as they were called, an estimated 22,200 were killed, almost twice the number killed in the whole period since May 1940. Some 55,700 buildings were rendered for the moment uninhabitable. ‘They had ruined the Ruhr,’ complained Hitler in June, though only 5 per cent of buildings were actually destroyed.94 The exact nature of the damage could not be known to Bomber Command, but intelligence estimates of the damage to the Ruhr were constructed in the summer to give Harris the necessary material to defend his city-bombing campaign. This was difficult to do and had to be based on extrapolation from the detailed statistical surveys of housing damage and man-hour losses in British cities bombed in 1941 and 1942. The Joint Intelligence Committee estimated that 9 per cent of the population of the most heavily raided cities were homeless (422,500) and 38.5 per cent (1,816,000) had housing damage. The committee estimated that 68,750 houses had been destroyed, a figure closer to the reality than might be expected from simple photo-reconnaissance. Estimating the impact on the economy was more difficult. The Krupp works in Essen were thought to have lost between one-quarter and one-half of planned output over the summer. The MEW estimated a total loss to German production of 10–12 per cent from attacks on the Ruhr-Rhineland (including 2–2.5 million tons of steel) and a bad state of morale.95 A study by the RE8 department two months later of the impact of the raids on Essen, based on studies of British workers during the Baedeker raids, concluded that if German workers reacted in the same way as British workers to the loss of housing and amenities, then Essen lost the equivalent of 50 city-days of work output. None of these efforts at calculating what Bomber Command was achieving were coordinated or consistent. Nor could they confirm whether bombing was a strategically sensible use of British resources.96
Alongside the night-bombing, the Eighth Air Force, as one senior American commander put it, ‘can only nibble at the fringes of German strength’.97 There were three small raids on German territory in March; one in April (a mission to Bremen which cost the loss of 15 per cent of the force); six attacks on the north German coast in May; and three in June, including the only attack on the Ruhr, against the synthetic rubber plant at Hüls on 22 June, where the loss rate was almost 9 per cent.98 The two forces were at quite different stages. In the first six months of 1943 Bomber Command dropped 63,000 tons of bombs, the Eighth Air Force only 8,400 tons more. For the American command, Operation Pointblank had not yet started; in contrast, the RAF, as the Director of Plans explained in March 1943, hoped that bombing ‘may well produce decisive results this year’. There was nevertheless no prospect that the two bomber forces would constitute what the Joint Intelligence Committee called after the Ruhr offensive ‘an organic whole’, because of continued American resistance to the idea that bombing cities was strategically useful. The Ruhr battle was one of a long line of Bomber Command campaigns in which the Eighth Air Force was largely absent.99
OPERATION GOMORRAH: THE DESTRUCTION OF HAMBURG
Back in November 1941 the Bombing Operations Directorate in the Air Ministry had concluded from a study of urban targets in northern Germany that Hamburg was the city which presented the best general conditions for a large-scale incendiary attack. Since the area was large, ‘saturation point’ would be harder to achieve. The report continued that if Hamburg was selected for special incendiary attack, ‘the whole of the effort should be confined to the congested city and housing areas North of the Elbe’. To get a clear picture of what saturation point might look like, the Directorate used a map of central London as a model, placing transparencies with a typical incendiary bomb salvo printed on them over the London streets to work out how widely the bombs would spread and how vulnerable the buildings might be.100 Over the winter of 1941–2 a great deal of effort went in to working out how to create a major conflagration with the existing technology. In February 1942 a further memorandum on choosing a German city to burn down had Hamburg at the top of the list, its vulnerability rated ‘outstanding’.101
Harris might well have tried to exploit that vulnerability in May 1942 when he planned the first 1,000-bomber raid, but poor weather prevented it. Had he done so, Hamburg would certainly have sustained far less damage and loss of life than proved to be the case when Harris finally decided, on 27 May 1943, that Hamburg would suffer next what he was inflicting on the cities of the Ruhr-Rhineland. What resulted in a series of raids appositely titled ‘Operation Gomorrah’ was the single largest loss of civilian life in one city throughout the whole European war, exceeded only by the 250,000 Japanese killed in the firebombing of Tokyo and the atomic attacks on Hiroshima and Nagasaki. The destruction of Hamburg in an uncontrollable firestorm on the night of 27–28 July 1943 is often presented as if it were an accident, the result of exceptional meteorological conditions and the failure of German defences, and not a product of deliberate intention. This is to misunderstand entirely the purpose of the city-bombing campaign, which was predicated from the start on causing as much general damage and loss of life as possible by means of large-scale fires. The firebombing of Hamburg was not exceptional. Not for nothing was its vulnerability rated ‘outstanding’; it was expected to burn well.
To understand the capacity of Bomber Command to inflict a conflagration of such intensity on Hamburg, it is useful to place it in the context of the long operational and scientific effort devoted by the Air Ministry to understanding how incendiarism worked. When the RE8 department was established in the summer of 1942, one of the first tasks given to it by the Air Ministry was research into the spread of fire and the role of wind speeds in turning a strong blaze into a conflagration. It was assumed that city fires could be acted upon much as a pair of bellows on a domestic hearth if the wind speed and direction were favourable. ‘Once a large conflagration has become established,’ wrote one of the department’s scientific advisers, ‘the “fire-storm” which it induces is sufficient to ensure its further spread.’102 On the advice of J. D. Bernal, wind trials were conducted by the Porton Down Experimental Station in Wiltshire using models of urban areas, while the RAF Photo-Interpretation section provided night photographs to help in identifying the factors which accelerated the spread of fire.103 It was also necessary to determine scientifically the vulnerability to firebombs of German urban structures, in particular town houses and apartment blocks, and the quantity and mix of bombs necessary to overwhelm the fire services in a single raid. Work on German structures began in 1942 and was more or less complete by the time of the final RE8 report on ‘German Domestic Architecture’ issued early in 1943. Tests on models of different kinds of German roofs were carried out at the Road Research Laboratory at Harmondsworth, outside London, while material on German staircases and stairwells was supplied from a German publication on ‘Residences and Houses of the Middle Classes’.104 The study of German architecture had involved a good deal of argument over the average thickness of wood beams and the penetrative power of the standard 4-lb incendiary bomb, which had only been resolved by recruiting émigré German architects, including the Bauhaus founder, Walter Gropius, to confirm the details of construction. The conclusion from studies of roof coverings, joists and floor density typical of construction in north-western Germany and Berlin was that ‘a German house will burn well’.105
The most important issue was to decide what mix and weight of bombs would best achieve a conflagration that was beyond the control of the ground defences. The quantity of incendiary and high-explosive bombs judged to be necessary to destroy each square mile of the target city was cranked up regularly during the two year
s before Operation Gomorrah. Initial research suggested that between 100,000 and 200,000 4-lb bombs would swamp any fire-watching and firefighting force, but they had to be dropped in large salvos, not in small packets.106 By late 1942 incendiary technique was better understood. Its purpose, as one Air Ministry report put it, was ‘the complete destruction by fire of the built-up area of a city’. This required a fire-raising group to isolate the target and start fires pronounced enough for the follow-up force to drop 25,000 incendiaries for each square mile attacked as well as high-explosive bombs to destroy windows, crater the streets, and intimidate civil defence and fire-workers. In order to start a conflagration the target area had to be the most densely packed residential areas of the city centre, Zones 1 and 2A on the zone maps supplied to Bomber Command. Igniting the ‘terraces of box-like buildings dating from the Middle Ages’ was, according to the Bombing Directorate, expected to ‘yield good dividend’.107
To prevent effective firefighting the incendiary load had to contain not only regular incendiaries but also the delayed-action explosive incendiary, capable of maiming or killing enemy civil defence workers and deterring them from action. These devices were deliberately timed to detonate at irregular intervals, some after three minutes, a small proportion only after ten.108 In late 1942 a small anti-personnel high-explosive bomb with a trigger fuse was developed, which could be activated by any object, even a jet of water, and would kill those immediately around it without warning.109 It was suggested that a high proportion of delayed-action bombs should be used in ‘incendiary attacks on virgin towns’ to create a powerful deterrent effect on the enemy emergency services.110 There was also considerable argument about the merits of complementing the conventional magnesium bomb with larger oil-based incendiaries, which were also subjected to rigorous scientific testing. The result was the selection of the 30-lb Mark II containing a mix of white phosphorous and benzol gel, capable of greater penetration than the 4-lb incendiary, and effective in spreading fire quickly over a wider area.111 All of these bombs were eventually produced and used in substantial quantities over the last three years of war, peaking in 1943 (see Table 6.3).
Table 6.3: Incendiary Bombs Dropped by the RAF, 1940–45
Year 4-lb bomb 4-lb explosive bomb 30-lb bomb No. 14 IB Cluster (106 × 4-lb)
1940 508,993 – – –
1941 2,082,669 – 758 –
1942 8,010,920 – 309,200 –
1943 25,898,290 1,469,853 1,728,949 –
1944 18,392,077 1,498,723 979,182 6,288,460
1945 6,761,544 690,523 – 3,764,670
Source: TNA, AIR 22/203, Bomber Command, War Room Manual of Operations 1939–1945, 54.
There was strong American interest in the development of incendiary bombing. The conventional view that the Eighth Air Force used predominantly high-explosive bombs for precision air attacks in contrast to the fire-raising tactics of Bomber Command is not borne out by the evidence. The Bombing Directorate in the Air Ministry collaborated closely with the American Office of Scientific Research and Development, which produced studies on the ‘Theory and Practice of Incendiary Bombing’, and supplied the British with illustrated volumes on major conflagrations in American cities, which were more common and more destructive than in Europe. The photographs resemble closely the aftermath of the major city-bombing in Germany.112 In October 1942 America’s foremost expert on fire in foreign countries, Boris Laiming, filed a report which was passed on to the Air Ministry in December. He argued that the only way to start a major conflagration under conditions normally prevailing in Germany was to start a great many smaller fires simultaneously on long strips of urban territory on a day when there was a reasonable wind and low humidity.113 In the United States, experiments were made at the Chemical Warfare Service depot in Utah in burning down different kinds of structure and at a facility in New Jersey on penetrating simulated German roofing with incendiaries.114 American expertise was also invited to Britain. Horatio Bond, chief engineer of the National Fire Protection Association, visited London for four months in late 1942 to give advice on large-scale fire destruction, followed a few months later by James McElroy, another senior NFPA engineer, who worked for the rest of the war at the RE8 headquarters at Princes Risborough in Buckinghamshire, first producing so-called ‘fire division maps’ of German cities, showing each urban ‘cell’ that needed to be set alight, then going on to produce vulnerability maps of major industrial targets for the Eighth Air Force Operational Research Section, to show what proportion and what type of incendiary bomb should be carried by aircraft.115
The American Air Force was impressed by British incendiary practice. In April 1943 Arnold spelt out for his assistant chief of staff for materiel the ways in which the Eighth Air Force would be expected to use incendiary bombs: first, for burning down precise industrial targets when a greater degree of destruction was possible using fire; second, by starting fires ‘in the densely built-up portions of cities and towns’ to create a beacon for RAF attacks at night on the same city or town; third, for burning down densely built-up areas ‘when the occasion warrants’.116 American forces used principally the 4-lb incendiary (renamed the M-50), the M-17 110-bomb cluster, the M-47 70-lb oil and rubber bomb, and the M-76 473-lb oil bomb. Extensive plans were laid in 1942 for incendiary bomb production, 39 million bomb cases in that year, 107 million in 1943, divided between the different services and Lend-Lease supplies for Britain.117 Extensive research on the effects of incendiary bombing resulted in a set of recommendations for the Eighth Air Force in September 1942, which differed from RAF practice principally by preferring the 473-lb oil bomb over the 4-lb incendiary and identifying weather as a vital condition: ‘a high wind is still the best weapon’. Bomb patterns were to be dense enough ‘to guarantee real conflagrations’.118 Extensive experiments were carried out in Britain on the use of oil bombs of different weights, and in April large quantities were finally shipped to American bases for operational use. They were first employed extensively in July 1943, the month of Operation Gomorrah. By the end of the war the Eighth Air Force had dropped a total of 90,357 tons of incendiaries and incendiary clusters, totalling 27 million 4-lb bombs and 795,000 heavy incendiaries.119
The two-thirds load of incendiary bombs aimed at the residential areas in Hamburg north of the River Elbe to try to stimulate an uncontrollable conflagration was thus no accident. The choice of Hamburg is not difficult to explain. The Air Ministry Target Committee in April 1943 defined Hamburg as ‘No 1 priority’ because of its shipbuilding industry.120 It had been attacked repeatedly since 1940, usually in small raids which inflicted light damage on Germany’s second-largest city. There were 126 small raids between 1940 and the end of 1942; the 10 raids in 1943 before Gomorrah resulted in just 100 deaths and the destruction of 220 buildings.121 Hamburg was fourth on the MEW list, behind Berlin, Duisburg and Bochum, all three of which had been attacked in the late spring. The MEW rankings in the ‘Bomber’s Baedeker’ had 21 industrial targets ranked 1+ or 1 and 25 ranked 2, substantially more than most other cities.122 The vulnerability of Hamburg was magnified by its proximity to British bases, the conspicuous coastline and its sheer size. In a survey of German cities already subject to incendiary attack, the ratio of incendiary to high-explosive damage in Hamburg was judged to have been 13:1, higher than any other except the port of Wilhelmshaven.123 It is not clear whether Harris was ever shown these figures, but his desire to launch a spectacular operation fitted with the geographical pattern of the new attacks and Air Ministry ambitions. Not to have attacked Hamburg in force would have been more difficult to explain.
The decision was nevertheless not easily endorsed and rested in the end on Churchill’s approval. The chief argument was over the decision whether to use a simple tactical device to temporarily blind all German radar, known by the codename ‘Window’. The tactic consisted of dropping very large quantities of small aluminized strips which would create a confused blur of echoes on enemy radar screens and make accurate
detection of the bomber stream impossible. It was first developed in late 1941 by Robert Cockburn at the Telecommunications Research Establishment in Malvern, and early trials led to the manufacture of the material with a view to using it against German radar in May 1942. Frederick Lindemann persuaded Portal to cancel the instruction and a fresh set of tests showed that the latest British ground and airborne radar was highly susceptible to ‘Window’ if the Germans retaliated with it. Lindemann insisted that it should not be used operationally until an antidote could be found. The Germans did develop the same technique, known as Düppel, but like the RAF, hesitated to develop and use it. However, by late 1942 new British AI radar for night-fighters and GCI radar for ground control, together with a new American airborne radar, SCR-270, all had the capacity to survive a ‘Window’ assault. American experiments also showed that maximum effect would come from a large number of narrow strips, about half as long as the wavelengths of the German Würzburg radar, which controlled the German air defences. ‘Window’ was manufactured in 30-cm strips, 1.5-cm wide, with paper on one side and aluminium foil on the other, in bundles of 2,000 for release from each aircraft in the bomber stream.124
The Bombing War: Europe 1939–1945 Page 45