Adolf Hitler, the German leader, expected Britain to surrender. However, the British, led by Winston Churchill, who had become Prime Minister on 10 May, had already resolved to fight on. Churchill made this clear when he said "the Battle of France is over. I expect the battle of Britain is about to begin".
After the collapse of France on 22 June, the British thought that invasion appeared to be an immediate threat. The situation was now extremely severe. The occupation by German forces of the whole of the European seaboard facing Britain threatened an even greater weight of air attack than had previously been feared.
However, Hitler did not decide until 16 July to proceed with an invasion. There was one obvious task to carry out before such an operation could succeed. The Luftwaffe had to win control of the skies over southern England long enough for German naval and land forces to make landings on the south coast. This aim would be achieved by destroying the RAF's fighter force. Without supporting air cover, the Royal Navy would have been neutralised, unable to oppose invasion forces in the face of overpowering air attack.
The German occupation of Denmark and Norway in April caused the weakening of the RAF fighter defences as squadrons had to be spread across northern Britain to oppose any possible threat from Scandinavia. In May and June, the Battle of France, especially the intensaive action during the evacuation of Allied armies at Dunkirk, had taken a heavy toll with 477 fighters lost and 284 pilots killed. All but three of Fighter Command's squadrons had been engaged.
On 3 June, Air Chief Marshal Sir Hugh Dowding, AOC (army operational command) -in-C Fighter Command, told Britain that if the expected German offensive came at this moment, he could not guarantee air control for more than 48 hours. Nevertheless, he was hopeful that a reasonable break from intensive operations would help to restore his Command to full strength. On 18 June the last fighter squadrons still in France returned to Britain. Measures were taken to extend the air defences to cover the west of England, west coast ports and western industrial areas.
After the Battle of France, in which it had suffered heavy losses, the Luftwaffe needed time to recover and re-equip and to combine its position on all the new airfields it had captured in France and the Low Countries. It suffered from supply problems, as German fighter production was 40% below target by summer 1940.
The break given to Fighter Command was well used. Sharply rising production between June and early August more than made up for the heavy losses in France. On 19 June, 520 aircraft were ready for operations. By 9 August, shortly before the launch of the full-scale German offensive, the number was 715, with a further 424 in storage units, available for use the next day.
Overall Summary
The Battle of Britain took place when the Luftwaffe attempted to win air power over southern England from the Royal Air Force as an essential must have for the invasion of Britain by German naval and land forces. For the British, it ran from 10 July - 31 October 1940. For the Germans it began on 13 August, Adlertag or "Eagle Day".
The key to success for the Luftwaffe was the destruction of the RAF's fighter force. On the other hand, for Fighter Command it was to hold back bombing and inflict losses, preferably before the target was reached. The campaign itself was marked by several distinct phases. As the battle developed, the Luftwaffe attacked targets moving further and further inland from coastal shipping to forward fighter airfields and radar stations, 11 Group sector airfields and finally London.
The crucial period of the battle was between 24 August and 15 September. Fighter Command came closest to losing when its vital sector airfields around London were attacked. The decisive turning point came on 7 September when the Luftwaffe switched its attention to the capital. This tactical mistake allowed Fighter Command to recover its strength rapidly to inflict, on 15 September, losses significant enough to show the Germans the battle could not be won.
