Japan would have to declare war at the beginning (before any units are moved) of its combat movement phase. So it would not be allowed to go through sz8, it would have to stop and battle that DD.
correction in 112 reason, you will need to judge whether you can afford to lose air or a ship if he is lucky enough to get 2 hits. Just remember what you bought and how much you can afford to replace air. I would lose a ship over air cause a ship does not help you sealion or barb as much as your air does.
Land and sea units that made a combat movement or participated in combat may not move during noncombat movement. Only one rocket attack per turn may be made against an individual industrial complex.
What stops US or UK placing 4-5 fighters in Gibraltar. Each would roll a 2 vs a 1 the escorting fighters if any(lack range i think) might get. Each Bombing raid would cost the attacker 1-2 bombers from defending fighters before you roll AA.
