'Adlerangriff' was the German all-out air offensive on the southern part of the UK, and known to the British as the Battle of Britain (10 July/31 October 1940).

This campaign was planned by the Germans to obtain a strategically decisive result by the elimination of the fighting strength of the RAF (by flying bomber attacks against coastal convoys, radar stations and fighter airfields to tempt up the British defences on tactical terms advantageous to the German fighters, which would then eliminate an RAF fighter strength that had been woefully underestimated by Luftwaffe intelligence, as had with production and repair rates), and thereby open the way for the intended Germans' planned 'Seelöwe' airborne and seaborne invasion of the UK.

The campaign pitted against the British the men and aircraft of Generalfeldmarschall Albert Kesselring’s Luftflotte II in north-western France and Generalfeldmarschall Hugo Sperrle’s Luftflotte III in north-eastern France and Belgium, supported by Generaloberst Hans-Jürgen Stumpff’s Luftflotte V in Norway. Between them these formations had some 3,320 aircraft (934 single- and 289 two-seat fighters, 1,482 medium bombers, 327 dive-bombers, 195 reconnaissance aircraft and 93 coastal aircraft) on 10 August, of which 2,550 (805 single- and 224 two-seat fighters, 998 medium bombers, 261 dive-bombers, 151 reconnaissance aircraft and 80 coastal aircraft) were serviceable, against Air Chief Marshal Sir Hugh Dowding’s RAF Fighter Command.

This latter’s most important elements in the Battle of Britain were Air Vice Marshal K. R. Park’s No. 11 Group in south-eastern England, Air Vice Marshal Sir Quintin Brand’s No. 10 Group in south-western England and southern Wales, Air Vice Marshal T. Leigh-Mallory’s No. 12 Group in East Anglia and the Midlands, and Air Vice Marshal R. E. Saul’s No. 13 Group in northern England with a total of 903 aircraft (754 single- and 149 two-seat fighters) on 11 July.

The failure of 'Adlerangriff', as a result of Reichsmarschall Hermann Göring’s overambitious attempt to win a strategic victory with what was essentially a tactical air arm, spelled the postponement and ultimately the cancellation of 'Seelöwe', and thus played a decisive part in the outcome of the war. Adolf Hitler was an avowed opponent of the concept of war on two fronts, but the failure of Germany’s plans against the UK meant that unless the proposed 'Barbarossa' invasion of the USSR was postponed, Germany would indeed be faced with two powerful opponents at the same time on different fronts.

With hindsight it is possible to see that the failure of 'Adlerangriff' was perhaps inevitable, for the Germans were attempting to achieve a strategic result with an air force designed specifically for the tactical support of the German army. And although useful results were achieved as long as tactical commanders were left in control of operations, the decision by Göring to tie his fighters to close escort of the bombers, which were being severely mauled by British fighters, meant that the fighters became almost as vulnerable as the bombers, increasing the German losses at a time when the British forces were close to the limits of their endurance. To cap it all, the Germans then decided to switch their forces away from the destruction of RAF airfields and fighters to the destruction of London, a politically motivated decision which gave the British fighters both a breathing space and just the targets they had been trained to tackle.

The Battle of Britain can be divided into a number of phases, the most useful being the four-phase arrangement comprising the 'Kanalkampf' (channel battle) over the English Channel (10 July/11 August), the 'Adlerangriff' or early assault against the coastal airfields (12/23 August), the critical phase against Fighter Command’s airfields (24 August/6 September), and the switch of the day attacks from airfields and fighter-related installations to British cities and towns (7 September until the start of the night 'Blitz').

The 'Kanalkampf' was a series of running fights over convoys in the English Channel, and was started in part because Kesselring and Sperrle were unsure about what else their forces should undertake at this time, and in part because it gave German aircrews some experience in fighting the British air units under new operational conditions and also a chance to probe the British defences. In general, these battles off the coast tended to favour the Germans, whose bomber escorts massively outnumbered the convoy patrols. The need for constant patrols over the convoys put a severe strain on the pilots and aircraft of the RAF, tiring the pilots and wasting fuel and engine and airframe hours, and eventually the number of ship losses rose to the level at which the Admiralty decided to cancel all further convoys through the Channel.

However, these early fights provided both sides with experience. They also gave the first indications that some of the aircraft, such as the RAF’s Boulton Paul Defiant turret fighter and the Luftwaffe’s Messerschmitt Bf 110 heavy fighter, were not suited to the type of dog-fighting which would characterise the main phases of the battle.

The weather, which was to prove an important feature of the campaign, delayed the launch of 'Adlertag' (eagle day) until 13 August. On 12 August the first attempt was made to 'blind' the radar-based control system used by Fighter Command when aircraft of a specialist fighter-bomber unit, the Erprobungsgruppe 210, attacked four radar stations, of which three were damaged but restored to serviceability within six hours. The raids appeared to show British radars were difficult to knock out for any length of time, and indeed the Luftwaffe’s failure to mount repeated attacks on them provided the RAF with the time to get the radar stations back on the air.

'Adlertag' opened with a series of attacks on coastal airfields, used as forward landing grounds for the RAF fighters. As the week continued, the airfield attacks moved farther inland and repeated raids were made on the chain of radar stations. The key day of this phase of the battle was 15 August, when the Luftwaffe mounted the largest number of sorties of the campaign.

This day also saw the one major intervention by the Norway-based Luftflotte V in the battle with an attack on northern England. Wrongly believing the strength of Fighter Command to be concentrated away in the south, raiding forces from Denmark and Norway ran into strong resistance. Inadequately escorted by Bf 110 fighters, bombers were shot down in large numbers. As a result of the casualties, Luftflotte V did not appear in strength again in the campaign.

On 18 August the battle reached an attritional peak with the greatest number of casualties on each side. After this, exhaustion and the weather reduced operations for most of a week, allowing the Luftwaffe to review its performance: on 18 August, for example, the Junkers Ju 87 dive-bomber made its last appearance in the campaign, having proved to be dangerously vulnerable to fighter attack over the UK, so to preserve the Stuka force, which was considered an essential adjunct to the German concept of land warfare, Göring withdrew it from the fighting. This removed the Luftwaffe’s main precision bombing weapon and shifted the burden of pinpoint attacks on the already hard-pressed Erprobungsgruppe 210.

The Bf 110 had also been revealed as too clumsy for dog-fighting against nimbler fighters, and its participation in the Battle of Britain was also reduced from this time onward, the type being used only when the range of a mission required its involvement or when sufficient numbers of escorts could not be provided.

Another fateful change ordered by Göring at this time was the use of the Bf 109 fighter for close escort of the bombers rather free-hunting sweeps. This limited the fighters' essential tactical flexibility, and the need to remain with the bombers meant flight at speeds which were uneconomical and therefore reduced the fighters' range and endurance over southern England. To achieve this the weight of the attack now fell on Luftflotte II, and many of the Bf 109 fighter units in Luftflotte III were transferred to Kesselring’s command, reinforcing the fighter bases in the Pas de Calais.

Stripped of its fighters, Luftflotte III now concentrated its efforts on the night bombing campaign.

Disappointed with the performance of the fighter units thus far in the campaign, Göring also made a large change in his fighter units' command structure, replacing many experienced Geschwaderkommodoren (group commanders) with younger, more aggressive pilots like Adolf Galland and Werner Mölders. Göring also ordered an end to the attacks on the British radar chain. These attacks had come to be seen as unsuccessful and indeed unnecessary as neither Göring nor his subordinates realised how vital the 'Chain Home' radar stations were to the defence. It was known that radar provided some early warning of raids, but the belief among German fighter pilots was, anything bringing up the British to fight was to be encouraged.

From 24 August the battle became an attritional campaign between Kesselring’s Luftflotte II and Park’s No. 11 Group of RAF Fighter Command. The Luftwaffe concentrated all of its power on knocking out Fighter Command and made repeated attacks on the command’s airfields in south-eastern England. Of the 33 heavy attacks in the next two weeks, 24 were flown against airfields. The key sector stations were hit repeatedly: Biggin Hill and Hornchurch four times each; Debden and North Weald twice each; and Croydon, Gravesend, Rochford, Hawkinge and Manston were also attacked in strength. No fewer than seven attempts were made against Eastchurch, which was not a Fighter Command aerodrome but was nonetheless believed to be so by the intelligence-starved Germans. At times these raids knocked out the sector stations, threatening the integrity of the Dowding command and control system.

These were desperate times for the RAF, which was also suffering a high level of losses in the air. Aircraft production could replace aircraft, but the flow of replacement pilots was barely keeping pace with losses, and novice fighter pilots were being shot down at an alarming rate. To help remedy the situation, at least in the short term, some 58 Fleet Air Arm fighter pilot volunteers were seconded to RAF squadrons, and a similar number of former Fairey Battle light bomber pilots, familiar with the Merlin engine, were utilised. Most replacements from operational training units had as little as nine hours flying time and no combat training.

At this point the multi-national nature of Fighter Command came to the fore. Many squadrons and individual personnel from the air forces of the dominions and empire were already attached to the RAF, in the form of Australians, Canadians, New Zealanders, Rhodesians and South Africans, and these were supplemented by the arrival of fresh Czechoslovak and Polish squadrons. These last squadrons had been held back by Dowding, who mistakenly thought the non-English speaking aircrew would have trouble working within his control system. In addition there were other nationals, including Free French, Belgian and even a Palestinian Jewish pilot serving amongst the squadrons. Polish pilots proved themselves to be very effective (the pre-war Polish air force had possessed lengthy, extensive and high standards of training) and with Poland conquered and under German occupation the battle gave the expatriate Polish pilots ample opportunity to vent their hatred of the Germans. They reportedly had no qualms about flying directly over the parachutes of bailed-out Germans, collapsing them and sending them falling to their death, or simply machine gunning them as they descended to earth.

The RAF also had the enormous advantage of fighting over home territory, so pilots who bailed out of their falling aircraft could be back at their airfields within hours. For Luftwaffe aircrews, exit from their aircraft over England meant capture, while parachuting into the English Channel often meant drowning or death from exposure.

Morale began to suffer and 'Kanalkrankheit' (Channel sickness, a form of combat fatigue) started to appear among the German aircrew. The German replacement problem was even worse than that of the British. Though the Luftwaffe always maintained its numerical superiority, the tardy appearance of replacement aircraft and pilots put increasing strain on the resources of the remaining attackers.

The Luftwaffe was nonetheless winning this battle of the airfields. Another fortnight of this pounding might have forced the RAF to withdraw its squadrons from the south of England. This fact was not clear to the Luftwaffe command, which had watched its bomber force being whittled away and had grown desperate to achieve the result desired for the launch of 'Seelöwe'. The Luftwaffe command could not understand why Fighter Command had not collapsed, or how it was always able to get fighters to the places needed, no matter how many raids were sent. Something needed to be done to force a decisive battle, therefore.

On 4 September, Hitler ordered the Luftwaffe to bomb London, following a RAF attack on Berlin launched on the night of 25/26 August after London and its suburbs had been unintentionally damaged by German bombs on several occasions late in August. The Berlin raid was a severe blow to the pride of Göring, who had previously claimed that the British would never be allowed to bomb the city. Kesselring seized his chance and proposed a strategy change. In the face of Sperrle’s arguments that the attacks on airfields should continue, Kesselring persuaded Göring to authorise attacks on London. The raids would either panic the British population into submission, or force the 'last 50 Spitfires' into the sky, where they could be annihilated. This attack was no longer seen as a prerequisite for 'Seelöwe', but was meant to be decisive in itself.

For several months before 7 September 1940, when the first major raid on London was launched, the Luftwaffe had bombed a series of British cities, killing more than 1,250 civilians in July and August. The 7 September raid targeted the dock area in the East End of the city, and over the following days large raids were launched, some targeting the docks but others bombing indiscriminately. The RAF did come up to contest the German effort, as the Germans had expected, but in altogether larger numbers than the Luftwaffe had thought possible. The 'big wing' (grouped squadrons of Leigh-Mallory’s No. 12 Group in East Anglia) was deployed for the first time, giving the German pilots a severe cause for concern. Over the coming days the attacks on London continued, but the break from bombing the airfields gave the RAF critical breathing space, and this was the turning point of the battle.

The most difficult part of the switch to attacks on London was the longer range. The Bf 109 escorts had a limited fuel capacity, especially when forced to fly as close escort for the bombers, and by the time they arrived over London they had a combat endurance of a mere 10 minutes before they had to turn for home. This left many raids completely undefended by fighter escorts.

The Battle of Britain culminated on 15 September with two massive waves of German attacks that were decisively repulsed by the RAF. The total casualties on this critical day were 60 German aircraft shot down versus only 26 British.

The German defeat caused Hitler, two days later, to order the postponement of 'Seelöwe'. Henceforth, in the face of mounting losses in men and aircraft, when there was also a lack of adequate replacements, the Luftwaffe switched from day to night bombing. The threat of a German invasion of the UK was essentially over, although the German night Blitz on London and other British cities continued into 1941.

Although the battle had been small in terms of the number of combatants and casualties, the Battle of Britain was of huge strategic importance as it marked the first defeat of Hitler’s military forces as air superiority had been seen as the key to victory. The British success was also reflected in a shift in US opinion at a time when many Americans believed the UK could not survive, a view promoted by Joseph Kennedy, the essentially anti-British US ambassador in London.

During the battle each side made exaggerated claims of numbers of enemy aircraft shot down. In general, claims were two to three times the actual numbers, largely as a result of the confusion inevitable in a fast-moving three-dimensional battle. Post-war analysis has shown that, between July and September, the RAF claimed more than 2,698 'kills' for 1,023 of its own fighters lost to all causes, while the Luftwaffe claimed 3,198 'kills' for 1,887 (including 873 fighters) of its own warplanes lost. To the RAF figure should be added an additional 376 Bomber Command and 148 Coastal Command aircraft conducting bombing, mining, and reconnaissance operations in defence of the country. The British lost 544 aircrew killed and 422 wounded, while the Germans lost 2,698 aircrew killed, 638 missing and 967 taken prisoner.

Some modern military historians have suggested the battle was unwinnable for the Luftwaffe because its numerical majority was not sufficient to achieve air superiority. The strategy of Dowding, who had the operational benefit of 'Ultra' intelligence as well as the tactical advantage of a superior radar-based command and control system, and his most important subordinate Park in choosing when to engage the enemy while maintaining a coherent force was vindicated. The much-vaunted current theories of strategic bombing’s importance, which predicted the collapse of public morale, were undone by British defiance in the face of the day and night Blitzes. The switch to a terror bombing strategy allowed the RAF to recuperate and to defend against the attacks. Even if the attacks on No. 11 Group’s airfields had continued, the British could have withdrawn to the Midlands, out of German fighter range, and continued the battle from there.

Post-war records show that the British were able to replace lost aircraft faster than the Germans could manage, and thus the RAF maintained its strength even as that of the Luftwaffe declined. The British were also aided by the fact that with the benefit of 'Ultra' intelligence, Dowding was also able to rotate his most exhausted units to quieter sectors to win the breathing space in which they could effect at least a partial recuperation before being cycled back into the front line once more.

In losses of aircraft and experienced aircrew the battle was a blow from which the Luftwaffe never fully recovered. The Germans launched some spectacular attacks against important British industries, but they could not destroy the British industrial potential. Hindsight does not disguise the fact the threat to Fighter Command was very real and for the participants, it seemed as if there was a narrow margin between victory and defeat. The victory was as much psychological as physical. The end of the Battle of Britain allowed the UK to start realistically on the task of rebuilding of its military strength after the disaster of the defeat in France during 'Sichelschnitt', the establishment of itself as an Allied stronghold and ultimately the base from which the 'Overlord' invasion of Europe could be launched.