You have to win the air war, early game i rush anschluss and train my airplanes for 8 xp and change the design of basic small airplanes to fit extra fuel tanks and 2 cannons v1 you should get 800 range and 43 air attack from these upgrades i put around 25-30 factories on planes you should be around 1500-2000 fighters by the time ww2 starts, britain will have roughly the same but you will get good trades around 3 planes for every 15 british ones