If UK and US are idiots, and the Germans and Japs geniuses, the Allies will lose.
If you attack a country with ground forces, whatever ground forces you attack with are committed.
For this reason, I like to have three USSR fighters and some artillery.
Tanks are a must-have; if Germany does massive infantry push, the tanks can rush back east to mess with Japan.
Basically, I usually build a fighter, LOTS of infantry, and a couple of artillery every so often.
