 Complete the following phrase:  German air doctrine had seen little need for the development of an nocturnal night air defence system and the Luftwaffe concentrated on the offensive use of air power. The failure of the Luftwaffe in the Battle of Britain in 1940 ended hopes for an early conclusion of the war. Faced with German domination of the continent, the only weapon the British could use to exert immediate military pressure on Germany was the night bombing operations of RAF Bomber Command. Bomber Command had been forced to operate at night since December 1939 and the 