Bombing, as Speer recognized, really did come to constitute a “Second Front” by 1943, preventing German military leaders from using airpower effectively at the fighting front as they had done in all the campaigns from 1939 to 1941. Failure in Russia, in the Mediterranean theater, and against the Allied invasion of France owed a great deal to the fact that German fighter aircraft, guns, ammunition, and radar equipment were tied up in the Reich.
