I'm sure it's been asked, but if someone attacks my subs and single DD with no DDs, a ship and some planes and a bunch of TTs doing an amphibious assault, he still has to do battle with my subs even after my DD is killed, right?
And if so, when he no longer has any units capable of hitting my subs, and I can no longer hit his planes, what happens to his TTs?
He retreats. The attacker always has the option to retreat. If you had transports, he could choose to remain, with his planes rolling against your transports and your subs rolling against his transports, but since he has no more legal targets, he either chooses to remain (losing the transports) or he retreats.