Germany's 8,000. The replacement of pilots and aircrew was more difficult. Both the RAF and Luftwaffe struggled to replace manpower losses, though the Germans had larger reserves of trained aircrew. The circumstances affected the Germans more than the British. Operating over home territory, British aircrew could fly again if they survived being shot down. German crews, even if they survived, faced capture. Moreover, bombers had four to five crewmen on board, representing a greater loss of manpower. On 7 September, the Germans shifted away from the destruction of the RAF's supporting structures. German intelligence suggested Fighter Command was weakening, and an attack on London would force it into a final battle of annihilation while compelling the British Government to surrender. The decision to change strategy is sometimes claimed as a major mistake by OKL. It is argued that persisting with attacks on RAF airfields might have won air superiority for the Luftwaffe. Others argue that the Luftwaffe made little impression on Fighter Command in the last week of August and first week of September and that the shift in strategy was not decisive. It has also been argued that it was doubtful the Luftwaffe could have won air superiority before the "weather window" began to deteriorate in October. It was also possible, if RAF losses became severe, that they could pull out to the north, wait for the German invasion, then redeploy southward again. Other historians argue that the outcome of the air battle was irrelevant; the massive numerical superiority of British naval forces and the inherent weakness of the Kriegsmarine would have made the projected German invasion, (Operation Sea Lion), a disaster with or without German air superiority. Change in strategy Regardless of the ability of the Luftwaffe to win air superiority, Hitler was frustrated it was not happening quickly enough. With no sign of the RAF weakening and the suffering many losses, OKL was keen for a change in strategy. To reduce losses further, strategy changed to prefer night raids, giving the bombers greater protection under cover of darkness. It was decided to focus on bombing Britain's industrial cities, in daylight to begin with. The main focus was London. The first major raid took place on 7 September. On 15 September, on a date known as Battle of Britain Day, a large-scale raid was launched in daylight, but suffered significant loss for no lasting gain. Although there were