World War II air battle part of the greater Battle of Britain
The Hardest Day was a Second World War air battle fought on 18 August 1940 during the Battle of Britain between the German Luftwaffe and British Royal Air Force (RAF). On that day, the Luftwaffe made an all-out effort to destroy RAF Fighter Command. The air battles that took place on that day were amongst the largest aerial engagements in history to that time. Both sides suffered heavy losses. In the air, the British shot down twice as many Luftwaffe aircraft as they lost. However, many RAF aircraft were destroyed on the ground, equalising the total losses of both sides. Further large and costly aerial battles took place after 18 August, but both sides lost more aircraft combined on this day than at any other point during the campaign, including 15 September, the Battle of Britain Day, generally considered the climax of the fighting. For this reason, Sunday 18 August 1940 became known as "the Hardest Day" in Britain.
By June 1940, the Allies had been defeated in Western Europe and Scandinavia. After Britain rejected peace overtures Adolf Hitler issued Directive No. 16 ordering Operation Sea Lion, the invasion of the United Kingdom. However, before this could be carried out, air supremacy or air superiority was required to prevent the RAF from attacking the invasion fleet or providing protection for any attempt by the Royal Navy's Home Fleet to intercept a landing by sea. Hitler ordered the Luftwaffe's commander-in-chief, "Reichsmarschall" Hermann Göring, and the "Oberkommando der Luftwaffe" (High Command of the Air Force) to prepare for this task.
The primary target was RAF Fighter Command. In July 1940, the Luftwaffe began military operations to destroy the RAF. Throughout July and early August, the Germans targeted convoys in the English Channel and occasionally RAF airfields. On 13 August, a major German effort, known as "Adlertag" (Eagle Day), was made against RAF airfields, but failed. The failure did not deter the Germans from persisting with air raids against the RAF or its infrastructure. Five days later came the Hardest Day.
Background.
The Luftwaffe was detailed to destroy Fighter Command before the planned invasion of Britain could take place. The "OKL" hoped that the destruction of the British fighter defence would force the British to come to terms by air power alone and the very risky Operation Sea Lion would not be needed. The enormous numerical superiority of British naval forces over their German opponents made a crossing of the Channel very dangerous, even with air superiority. Furthermore, the aircraft losses of the spring campaign had weakened the Luftwaffe before the Battle of Britain, and it could not begin its campaign against Fighter Command immediately. It was forced to wait until it had reached acceptable levels before a main assault against the RAF could be made in August 1940.
Until the Luftwaffe was ready to begin operations over the mainland, the first phase of the German air offensive targeted British shipping in the Channel. The raids rarely involved attacks against RAF airfields inland, but enticed RAF units to engage in battle by attacking British Channel convoys. These operations lasted from 10 July to 8 August 1940. The attacks against shipping were not very successful, and only 24,500 GRT was sunk. Mine laying from aircraft had proved more profitable, sinking 38,000 tons. The impact on Fighter Command was minimal. It had lost 74 fighter pilots killed or missing and 48 wounded in July, but British strength rose to 1,429 by 3 August, leaving it short of just 124 pilots. Still, the attacks succeeded in forcing the British to abandon the Channel convoy route and to redirect shipping to ports in north-eastern Britain. With this achieved the Luftwaffe began the second phase of its air offensive, attacking RAF airfields and support structures in Britain.
The month of August witnessed an escalation in air combat, as the Germans made a concentrated effort against Fighter Command. The first major raid inland and against RAF airfields came on 12 August, and the Luftwaffe quickly escalated its offensive. The Germans did not achieve a degree of success commensurate with their exertions on this date. Nevertheless, in the belief they were having considerable effect on Fighter Command, they prepared to launch their all-out assault on the RAF the following day. By 13 August, German air strength had reached acceptable levels. After bringing its serviceable rates up, the Luftwaffe carried out heavy attacks under the codename "Adlertag" (or Eagle Day), with 71 per cent of its bomber force, 85 per cent of its Messerschmitt Bf 109 fighter units, and 83 per cent of its Messerschmitt Bf 110 heavy fighter/fighter-bomber units operational. The day went badly for the Germans, who failed to impair Fighter Command and its bases or command and control system. This was due in large part to poor intelligence, which failed to identify Fighter Command airfields and distinguish them from those of Bomber and Coastal Commands. Still, the Germans pursued their strategy against Fighter Command on 15 August, suffering 76 losses. Undeterred, they prepared to make another large-scale attack on RAF bases on 18 August.
Luftwaffe plan.
German intelligence suggested that the RAF was down to just 300 serviceable fighters on 17 August 1940, taking into consideration German pilots' claims and estimates of British production capabilities. In fact, there were 855 machines serviceable, with another 289 at storage units and 84 at training units. These resources were included in a total of 1,438 fighters, twice as many as at the beginning of July 1940. Expecting weakening opposition, the Luftwaffe prepared for a major action against RAF Sector Stations on 18 August.
The Luftwaffe's plan of attack was simple. German bombers were to strike at the RAF airfields in the south-east corner of England. The most important airfields in this region, under the command of AOC (Air Officer Commanding) Keith Park and his No. 11 Group RAF, were the Sector Stations at RAF Kenley, Biggin Hill, Hornchurch, North Weald, Northolt, Tangmere and Debden. The first five were on the periphery of Greater London. Tangmere was in the south near the coast at Chichester, while Debden was north of London near Saffron Walden. Each of these airfields housed two to three squadrons and had its own sector operations room. From there, its fighters were directed from its satellite airfields into combat. There were six satellite airfields at Westhampnett, Croydon, Gravesend, Manston, Rochford and RAF Martlesham Heath; Manston and Martlesham Heath each housed two squadrons, the remainder each housed one. Finally, there was RAF Hawkinge, just inland from Folkestone. Not all of these airfields were targeted on 18 August.
Despite the failure of "Adlertag" and considerable loss rates on 15, 16 and 17 August, Kesselring convinced Göring that the only sound strategy was to continue to send heavily escorted bombers to destroy British airfields. Kesselring also advocated the use of "Jagdgeschwader" (fighter wings) in free-chase tactics. Messerschmitt Bf 109 single-engine fighters were to be sent out in advance of the main raids to force the British fighters into large-scale air battles which, in theory, would destroy RAF aircraft in combat and deplete the British defences. However, this time, Kesselring changed his operational methods. In consultation with Hugo Sperrle, commanding "Luftflotte 3" (Air Fleet 3), he chose not to scatter his effort against a large number of targets. Instead, he narrowed down the targets to a short list in order to concentrate his strength and striking power. Sector stations RAF Kenley, North Weald, Hornchurch and Biggin Hill were chosen as the prime targets.
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RAF defences.
Initial strategy and tactics.
Up to the late spring of 1940, Fighter Command had been preparing to meet a possible air attack on the British Isles coming only from due east, from Germany itself; prior to the German victory in Western Europe. The possibility that France might fall and Britain would continue to fight on had not been considered. An air attack from Germany meant the Luftwaffe's bombers would operate beyond the range of their fighters and be vulnerable to attack. If twin-engine fighters, such as the Messerschmitt Bf 110s were used, they would be fighting at the limits of their range.
It was also doubted that fast fighter aircraft could engage in dogfights. The g-force effect on the human body also seemed to suggest the prospect of air-to-air combat between fighters was impractical anyway. The threat they saw related only to the return-fire of the bomber's gunners. Before the war the effectiveness of return, or cross-fire, from bombers had been exaggerated by the Air Staff and Air Ministry.
This short-sighted belief had a detrimental impact on the tactical effectiveness of RAF Fighter Command until the summer, 1940. With German bombers perceived as the only prey, AOC Fighter Command Hugh Dowding and his planners devised a system and tactics which used unwieldy and tight fighter formations to bring the RAF fighters into combat with bombers, followed by set-piece tactics for the engagement. Because the bomber's return fire was considered so dangerous, fighter pilots were trained to open fire at long range, 300 to 400 yards, then break away without closing to short-range. These tactics, practised so thoroughly over the years, proved totally useless in the battle situation facing them over Britain in 1940.
The tactics were also unsuitable for fighter-versus-fighter combat. Packed in tight formation, the RAF pilots were more concerned with keeping their position and not colliding with each other than they were keeping watch for the enemy. It made them vulnerable to surprise attacks by Bf 109s and Bf 110s. Even if the British fighters reached the bombers without interception, the chaos of modern aerial combat made it impossible to concentrate attacks with large, rigid formations. Pilots were also forced into paying far too much respect to the bomber's defensive capabilities. Attacks were broken off far too early and caused little damage to bombers. These tactical failures were evident during the battles in Belgium and France. Moreover, rushed training with pilots who were barely able to use the old tactical methods meant that airmen could not cope with much needed radical changes.
The V or Vic formation was developed in June, which made a greater emphasis on each pilot looking for the enemy, search capability and avoiding being taken by surprise. Still, it was inferior to German fighter tactics.
German fighter tactics were more flexible. In the Spanish Civil War, Werner Mölders developed a new system of fighter tactics. The primary deployment was to use large numbers of Bf 109s on free-hunting missions, or sweeps, over the battle area. Instead of flying the standard V formation, used by many air forces, the Germans paired their fighters into "Rotte". It consisted of two fighters; a pilot and his wingman 200 yards abreast. Flying this way meant each could cover the others blind spots. If an enemy made an attack, the other could move in behind it to protect the other "Rotte" member. The "Rotte" could be expanded into a "Schwarm" (Swarm or Flight). The formation was eventually given the name "Finger-four". It offered maximum protection and all members of a "Schwarm" were on the lookout for threats and targets.
C3: Command, communication and control.
At the operational level the British fighter defences proved to be far more sophisticated. The RAF defences were not just based on the combat power of Fighter Command. Just as important as the "teeth" of the defence was the "eyes and ears" – its nervous system which carried intelligence and information between them to position the "teeth" to strike.
By the summer, 1940, the Chain Home radar stations along the English and Scottish coasts were able to track incoming aircraft from continental Europe at all but the lowest altitudes. The best detection altitude was . Aircraft at this height could be detected over away. To assess their identity, IFF (Identification Friend or Foe) could, by means of a distinctive blip on radar screens, distinguish German and British aircraft.
The radar technology was not flawless. It struggled to gauge heights of incoming formations above and could not measure their numerical strength. It could also take several minutes to assess the line of advance for aircraft on a zigzag course. Moreover, the radar looked out to sea and was unable to track aircraft overland. That was the job of the Royal Observer Corps. Tens of thousands of volunteers, the length and