I do similiar moves with China. I don’t allow any walk ins, I want a chance to kill an infantry unit in every territory Japan walks into. I’ll keep a mass (or as many as I can mass up) of infantry behind the front lines with the fighter as a counter attack force. If Japan can muster a ground force larger then I think I can counter attack and kill I’ll move my mass further back and to the north so ultimately it will cost Japan an extra turn of movement when China does die and they go after India. I’m always looking to counter attack. If you can get the Brits and China working together to keep Yunan from falling to the Japanese that’s great too, but, it really depends on how the game progresses.
