Thank you all for the replies! I was the USSR and France in an Allied Victory. The Axis player waited to attack all of the major powers until round three and by that time we were too built up for him to push very far into one area.
Note that for #3, if the UK does not declare war on Japan the battleship could stay in the zone (would not be hostile), but if Japan has declared war on the US, there is almost no reason for the UK not to declare war on Japan… So in 99% of cases I suppose the UK BB would need to move (if UK declared war on Japan since Japan DOW on USA)…
another example of this in action is attacking an enemy sub. He might (and probably will) submerge, but its up to the defender so the attacker needs to send enough hardware to the sz to win if the enemy defends.