Enemy subs can be attacked or ignored at will by the acting player. The only effects that a destroyer has are to suppress subs special abilities and to allow air units to hit them.
‘sub’ stall is not a term we’ll be using in this game.
The only way to force combat or make a fleet stay is to drop a surface vessel. Most likely a DD.
Hm - so it is possible for China to rake in 5 infantry per turn after all. Interesting.
Oh, and Wilson2, you didn’t give credit to Japan as being a possible controller of the UK. With long range heavy bombing paratroopers, anything’s possible.