After the fall of France, the Germans needed air superiority over Britain’s Royal Air Force to facilitate invasion under Operation Sealion. There had been mass Allied evacuation across the Channel from the French western ports in June 1940, and the following month the Luftwaffe launched attacks on ships in the Channel and on English coastal towns. The RAF, benefiting from fighting over home territory and the advantage of radar, proved to be tough opposition. After a failed attempt in mid-August to eliminate Fighter Command (‘Adler Tag’ or ‘Eagle Day’), the German bombers focussed their attacks on airfields, factories and radar stations. On 7 September a change of tactic saw bombing begin in London – the start of the Blitz – which continued until a daylight raid on 15 September, known as Battle of Britain Day, when the RAF successfully scattered the Luftwaffe and secured British skies. Although more bombs fell on British cities after the Battle of Britain ended, it was clear that the RAF would not be overcome.