On 15 September, two massive waves of German attacks were prevented by the RAF, with every aircraft of 11 Group being used that day. The total casualties on that important day were 60 German and 26 RAF aircraft shot down. The German defeat caused Hitler to order two days later a delay of the preparations for the invasion of Britain. In the face of increasing losses in men, aircraft and the lack of good replacements, the "Luftwaffe" later switched from daylight to night-time bombing.