@frimmel:
If the UK player does not move his BB during combat movement he is forced into combat with the sub. He is free to move it and avoid combat with the sub. He may move it to another enemy occupied sea zone to begin combat, a freindly sea zone or an empty sea zone.
You described the only situation where you can have opposing units in the same space at the end of turn.
If the UK BB stays and combats the sub and misses and the sub submerges then on the sub’s owner’s turn the sub is in the same situation as the BB ship was. It must move away or stay and fight the BB. Hope that helps.
Just to follow up on this scenerio…
Say the UK BB then stays to fight the sub, but misses and the sub submerges so you still have the sub and BB in the same sea zone.
Now, a US DD attacks the sub. The UK BB is NOT included in the battle, right?
So the US DD attacks, but the sub scores a hit, you cannot take the hit on the UK BB, right?