Got this game a few weeks ago, going as Britain is too easy, hammered the Italians in North Africa and nicked it all off them, and battered the Japanese and Siam (who tried invading Singapore while my back was turned).
Just park the Home Fleet outside Wilhelmsaven and the Kriegsmarine can’t get out (they’re not strong enough to fight the RN), put the reserve fleet outside Brest (if the Germans capture the French Navy) for the same result. Then all you have to do is sit and build your army up until you’re strong enough to recapture France (I was on my way to doing it without America joining the war and 2 years early).
Tried it as the Germans, and it’s bloody hard. You cannot build your fleet up to try and fight the British without weakening your army and air force (both of which need to be very big to try and take Poland, France and the Low Countries).