1939 Japan

I like to sit back and play defensive for the first few rounds. Knock out the Chinese generals as they rush your troops in Manchuria (if you must, send reinforcements like Itagaki to push back the Chinese). Once you knock out most of their generals, start taking the cities. Meanwhile, you can send Yamashita and a few others (I sent Okamura and a couple of tanks) to Moscow once you're confident that Asia has been secured. The Soviets should be busy with the Germans by then, so don't expect them to be guarding Moscow unless you attack too early.

The admirals should focus on annihilating the US Pacific Fleets. Once that was over with, I had them enter passive mode (until the mop-up phase of the conquest), where they just sat back and destroyed any Australian/US ships that came to challenge them. You can send them to Australia, though, but be careful of the artillery general (Blamey) in Brisbane.

Rest of the conquest should be easy. Japan starts off with so many generals and admirals, so it shouldn't be too difficult.