Those who argue that historiographical consensus about a past event is impossible to achieve and that any event is always open to revision from another perspective need to exercise caution.
Saluting the Few: The triumph of British Air Power in 1940
‘IF WE LOSE THE WAR IN THE AIR, WE LOSE THE WAR, AND WE LOSE IT VERY QUICKLY’ - Field Marshal Montgomery
Those who argue that historiographical consensus about a past event is impossible to achieve and that any event is always open to revision from another perspective need to exercise caution. Good history, as opposed to journalistic hyperbole, treats facts with scientific rigor, demonstrating proof of cause and effect. In attempting to explain what caused the German hierarchy to postpone indefinitely their plans to invade Britain in the late summer of 1940, the historian’s task is made comparatively easy by the existence of a number of unassailable facts. Most importantly, there is a clear causal connection between the Luftwaffe’s failure to achieve air superiority and failure to force Britain into submission through bombing, coupled with a sustained assault on enemy ports by Bomber Command and aggressive anti-shipping and patrol work undertaken by Coastal Command, and Hitler’s decision to postpone indefinitely and then cancel Operation Sealion. When Churchill saluted ‘The Few’ in his famous speech to the House of Commons in 1940, he made a point of honouring Bomber and Coastal Commands as well as Fighter Command. So, air power in the round was the principal instrument ensuring Britain’s survival in 1940.
In order to prove the causal link between the RAF’s victory in 1940 and Hitler’s decision to postpone and then abandon plans to invade Britain, we must necessarily begin with the Germans’ own threat assessments and decision making in the months leading up to the Luftwaffe’s air assault on Britain. Meaningful planning for an invasion did not commence until after the British Expeditionary Force’s withdrawal from Dunkirk and the French surrender of 22 June 1940. Prior to that point, contingency studies performed by the Wehrmacht and the Luftwaffe were dismissed by Hitler, who argued that the risks associated with an invasion were far too great. Up until the beginning of July 1940, Hitler and other leading party members remained confident of a political solution to the ‘British problem’. This is evident from a memorandum issued on 30 June by Hitler’s chief military adviser, Maj-Gen Jodl, Chief of the Wehrmacht’s operations staff: ‘If political measures do not succeed, England’s will to resist must be broken by force’. Of particular importance to our argument, however, is the fact that Jodl identified the elimination of the RAF as the key to defeating Britain, and that an invasion would only be attempted as a last resort and that an invasion would be entirely dependent upon the Luftwaffe achieving air superiority. Therefore, it is clear that Jodl and others regarded invasion as a coup de grace after the Luftwaffe had rendered Britain defenceless.
A Directive issued on 2 July showed that Hitler was also subscribing to the view that attaining air superiority was the most important prerequisite for an invasion, but Hitler’s lack of enthusiasm for an amphibious landing was also implicit in his decision making: ‘The Fuhrer and Supreme Commander has decided that a landing in England is possible, providing that air superiority can be attained and other certain necessary conditions fulfilled. The date of commencement is still uncertain’. The Kriegsmarine and the Luftwaffe were ordered to provide the Wehrmacht High Command with estimates, but it was plain that preparations for the invasion had not gone beyond the planning stages. The first Joint Army-Navy meeting to discuss the invasion option did not occur until 1 July. The Kriegsmarine’s assessment, based on studies into its fitness in relation to the Royal Navy undertaken since May, concluded that an invasion would prove a difficult and hazardous undertaking. Of particular concern was the need to make good naval losses incurred in the Norwegian campaign, and to increase the merchant shipping tonnage required to ferry an invasion force of 100,000 personnel with all its materiel to Britain. Another Kriegsmarine Naval Staff assessment, also promulgated in July, concluded that it was inadvisable to launch Sea Lion before 1941. But, more ominously for the Wehrmacht, a Naval Staff document prepared at the same time warned that the Kriegsmarine would be unable to protect a Channel crossing from attacks by the Royal Navy. Of particular concern was not only the Royal Navy’s capital ships but also the flotilla of 800 or so fast attack craft, especially Motor Torpedo Boats. In view of these assessments, the Wehrmacht High Command altered its planning assumptions, and not only did they feel compelled to reduce the landing area to half of that originally envisaged (down to a 150 km zone adjacent to Calais), but, by the end of July, the Commander in Chief of the Wehrmacht, Field Marshal von Brauchitsch, and the Chief of the General Staff, Halder, agreed that the Wehrmacht could not carry out its part of the Sealion operation ‘on the basis of the resources furnished by the Navy’.
By 31 July, the enthusiasm for an invasion was at a low ebb. On that day, the Commander in Chief of the Kriegsmarine, Admiral Raeder, informed Hitler that the Navy’s preparations for a landing could not be concluded before the middle of September. This was also the day that Hitler issued his Fuhrer Directive No 17, instructing the Luftwaffe to commence its air assault on Britain. If the results of the air campaign were satisfactory, then an invasion would take place at some point after mid-September, but if the RAF could not be defeated, then preparations for an invasion would cease. On the following day, 1 August, a new Directive instructed the Luftwaffe to defeat the RAF ‘with all means at its disposal’. What this German decision making demonstrates is that Hitler and the Wehrmacht and the Kriegsmarine all regarded the Luftwaffe as the principal instrument for defeating Britain in 1940. Evidence also shows that Maj-Gen Jodl regarded the air war as an important means for Germany to ‘spare her strength and avoid risks’.
However, perhaps most striking of all is Jodl’s belief that the RAF posed not merely a tactical or operational level threat to German aspirations in Europe, but that its very existence threatened Germany at a fundamental, strategic, level. He stated: ‘The war against the British air force must be the very first task in order to reduce and finally to stop the destruction of the foundations of our war economy’. In other words, the successful outcome of the air campaign launched against Britain meant everything to the Germans. They saw a clear connection between the RAF’s survival and Britain’s survival, and that an intact Britain spelled the end of Germany’s long term ambitions. In retrospect, with the full weight of evidence at our disposal, we know that this judgement was correct. By staying in the fight, Britain was able to bomb Germany and later contribute to the Combined bomber offensive; the Royal Navy and Coastal Command went on to play decisive roles in the Battle of the Atlantic; and Britain provided the crucial staging point for D-Day and the eventual liberation of Europe.
The direct connection between the RAF’s effort and the German decision to postpone and then cancel Sealion also cannot be disputed easily. Although the RAF as a whole suffered appalling losses throughout what is generally considered to be the whole Battle of Britain period (10 July – 31 October 1940), a total of 1,535 aircrew, the Luftwaffe lost more heavily (2,662 men). Crucially for the purposes of this argument, the Luftwaffe suffered the greatest losses in the month leading up to 15 September. It lost 1,132 aircrew and 862 aircraft. While losses across all the RAF Commands are difficult to discern in the same period, we know that Fighter Command had 201 killed and 493 aircraft shot down or effectively lost during the same period. German intelligence, while less successful than British intelligence in this phase, had sufficient material derived from SIGINT and other communications intercepts to know that Fighter Command had not been beaten. (The extent to which Fighter Command was almost fatally weakened, however, was not appreciated by the German analysts). This partial intelligence understanding prompted Hitler to order the Luftwaffe to redirect its attacks away from Fighter Command’s sector stations in the southeast of England to assaults on the cities, especially London in the hope of delivering a finishing blow to British morale. Thus, a new phase of the air campaign, and a new strategy for defeating Britain, began on 7 September.
This change in strategy prompted by the Luftwaffe’s failure to eliminate Fighter Command was fatal for the Germans. Fighter Command’s continued existence had two very serious implications for the German effort. First, it gave Fighter Command and 11 Group in the southeast, in particular, a vital breathing space and enabled a vigorous riposte to any attempt to bomb London or other cities. Second, the prime prerequisite for an invasion, namely, air superiority, had not been achieved.
For a week after the change in German strategy, preparations were still underway for an invasion. On 17 September, however, Hitler postponed Sealion indefinitely. In the intervening time, the RAF as a whole had stepped up its effort. The RAF’s Photographic Reconnaissance Unit (PRU) revealed that the Germans had mustered some 1,600 invasion craft in ports and anchorages between Boulogne and Antwerp. While Enigma decrypts of German high grade signals provided few clues as to a probable invasion date, what this SIGINT did reveal was that a new invasion support organisation had been placed on a high state of readiness. In light of these two major sources of intelligence, Coastal Command was tasked with continuous patrol work and anti-shipping operations in the Channel. The enemy occupied coastline from Dunkirk to Dieppe and from Le Havre to Cherbourg was covered at least twice in a 24 hour period; between the Hook of Holland and Ostend there was a continuous patrol, including during the hours of darkness; and major patrols were mounted off the Norwegian coast and North Sea to cover a potential secondary invasion route from Norway. Bomber Command, meanwhile, was directed to attack the German occupied ports along the Channel coast. The RAF’s Air Intelligence branch recorded that vast sections of the French coastline had been set on fire by Bomber Command’s attacks. The German record for the same period shows that there were particularly heavy bombing raids on 14, 15 and 16 September, and that there had been significant shipping losses at Le Havre, Calais, Dunkirk and especially at Antwerp, where a large ammunition depot had also been hit. Although post-war weapons effect research showed that only 10-12% of the German invasion fleet had been destroyed by this bombing, the Germans were sufficiently startled by the bombing to begin withdrawing their invasion shipping to German ports beyond the range of the RAF’s bombers. But, most significantly for the purposes of our argument, surviving German records show that reports on the bombing were sent to Berlin by both the Wehrmacht and the Naval High Command staff.
Hitler’s decision to postpone Sealion also followed some of the Luftwaffe’s heaviest casualties and hardest fighting in the skies over England. Daylight attacks on London began in earnest on 7 September, and although this switch to the capital caught 11 Group by surprise, it was never caught unawares again. Each subsequent attack on London met with stiff opposition by Fighter Command, especially on 9 and 15 September (the date usually commemorated as ‘Battle of Britain Day’). On 15 September, the Luftwaffe lost over 50 aircraft, one of its heaviest defeats since the start of the war. This turn around in the Luftwaffe’s fortunes was not only the result of the breathing space afforded 11 Group by the change in German strategy, nor even merely the consequence of an integrated air defence organisation now working like a very well oiled machine. The improved circumstances also reflected intelligence support to Fighter Command. Most accounts of the Battle of Britain pay scant attention to the intelligence aspects, beyond a brief mention of Ultra. Enigma decrypts were extremely useful for providing an accurate picture of the Luftwaffe’s Order of Battle. However, what Fighter Command needed on a day to day, and hour by hour, basis was intelligence of use to operations. By the beginning of July 1940, the Government Code and Cypher School at Bletchley Park had broken the codes used by German aircraft in Wireless Telegraphy (W/T) transmissions. As the Battle of Britain progressed, this lower grade SIGNINT could be calibrated with returns from radar stations. However, the most valuable intelligence started to appear in the last half of August, when Luftwaffe aircraft regularly flouted operational security measures, and broadcast W/T and radio signals in plain language. Such SIGINT frequently betrayed not only the direction and altitude of enemy aircraft, but also vital indications of where these aircraft would rendezvous for the flight back to bases in France. Luftwaffe accounts from this period often expressed surprise at the regularity and success of Fighter Command interceptions.
By 10 September, the Luftwaffe’s High Command staff were reappraising the air situation, and concluded that Britain was absorbing its losses and would be able to hold out until either the Luftwaffe was destroyed or the United States intervened. The Luftwaffe did not appreciate it at the time, but the tide had, indeed, turned in another significant way by mid-September. The week beginning 7 September was the first week in the Battle of Britain period where losses of Hurricane and Spitfires did not exceed the output of the British aircraft industry. The significance of the Luftwaffe High Command’s assessment of 10 September should not be under-estimated, and it is surprising that this evidence receives only a passing mention by the German official historians. Although Goring outwardly remained optimistic that the Luftwaffe could achieve a psychological blow against the British population, Hitler and other senior command figures were more cautious. On 14 September, Hitler stated that one of the reasons he had not officially cancelled Sealion was that he wanted to maintain the psychological pressure on the British populace. So, in a strange reversal of what was originally expected from an air campaign, the threat of invasion was now being used to support the air war. Hitler went on to say that ‘outbreaks of mass hysteria may yet occur in Britain’. But it is clear that Hitler’s hopes of the air war subduing Britain in the way he wanted now resided in the realms of wishful thinking. The Chief of the General Staff, General Halder, also commented that there had been no ‘mass panic’ in London or elsewhere.
Thus, by the middle of September 1940, not only had the Luftwaffe failed to achieve the air superiority identified as the chief prerequisite for an invasion, but the British people refused to be cowed into submission. These basic facts, plus shows of force and tenacity by Bomber and Coastal Commands, all fed into German decision making about Sealion. While the Royal Navy had been a major concern to both the Wehrmacht and the Kriegsmarine when ideas of an invasion were first mooted, and remained an underlying deterrent, the campaign, and arguably the whole war’s, fulcrum was in the air.
Author: Christina J.M. Goulter
Dr. Christina J.M. Goulter is Senior Lecturer in Defence Studies, King’s College London, and Air Warfare Historian on the Higher Command and Staff Course, Joint Services Command and Staff College, Defence Academy of the UK.
 House of Commons Debates, Vol. 364, Col.1167.
 Taylor, T.& The Breaking Wave (Simon and Schuster, New York, 1967), p.44. See also Umbreit, H., ‘Plans and Preparations for a landing in England’, in Germany and the Second World War (Clarendon, Oxford, 1991),, Vol.II, pp. 367-368.
 Taylor, T. op. cit., p.54. See also pp.57-70; Umbreit, op. cit., p.369; Von Plehwe, F. ‘Operation Sealion, 1940’, RUSI Journal (March 1973), p.51.
 Maier, K. ‘The Battle of Britain’, Germany and the Second World War, p. 374. See also p. 375, and Butler, J.R.M. Grand Strategy, Vol.II (HMSO, London, 1957), p.284.
 Quoted in Maier, op. cit., p. 374.
 Terraine, J. The Right of the Line (Hodder and Stoughton, London, 1985), p. 206f; Hinsley, H. et al, British Intelligence in the Second World War (HMSO, London, 1979), Vol.I, pp.168-190.
 Hinsley, F. op. cit., Vol.I, pp. 188-189; Goulter, CJM, A Forgotten Offensive: Royal Air Force Coastal Command’s Anti-Shipping Campaign, 1940-1945 (Frank Cass, London, 1995), pp. 121-123; Terraine, J. op. cit., p. 210; Taylor, T. op. cit., p. 276; Maier, K. op. cit., p. 396.
 Richard, D. Royal Air Force 1939-45, Vol. I, ‘The Fight at Odds’, (HMSO, London, 1974), p.190f; Taylor, T. op. cit., p.275; Hinsley, F. et al op. cit., pp. 180-182.
 Maier, K. op. cit., pp. 389-391, 396; Richard, D. op.cit., pp. 191 and 180f.