Even if Russia collapses this winter the German Air Command will have many difficulties to surmount before it can build up the German Air Force into a highly trained and operationally perfect machine to undertake a major operation against the British and American organised air defences in the British Isles. By, say, August 1943 some 4,000 aircraft (I.E. Plus I.R.), which would include about 1,000 single-engined fighters, might be concentrated on the Western Front. Allowance has been made for the retention of approximately 1,750 aircraft for the Mediterranean area, Caucasia, security purposes on the Russian Front, a skeleton force in Norway and for a minimum force refitting in Germany.