I usually build a ton of infantry to protect my capital early on. That way for the rest of the game I don’t have to worry about it. Just keep building tanks and hitting Russia in the east. Use every single plane you have no matter where it is located. If it is in Western Europe, fly it over to Ukraine. Hit them with everything you’ve got. This will cripple both of you, but as long as the Japanese player is smart enough to take them in the East, then you will come out on top, because you will have almost twice the economic might and will be attacking them on two fronts.
Also get a tank or two over to Africa and blitz through the open countries there. It will really put the kaybosh on the British player launching any decent offence against you, cause he will have no money