why would we care if a nuclear armed sub is 10 km off our shores? what's it going to do... it's not going to for them, and of it is them lions spent on MPA will have solved nothing because they could still fire ICBM from home, what another 10 minutes flying time..
Well, not saying this is whats going to happen, but.
Thats ten minutes you have to launch every thing you have, or get into motion the ability to get back at them.
I would hazard a guess, that getting in a first knockout punch is the name of the game.
So bad guys MO is, to develop the ability to limit your responce. The good guys, thats us, is to make sure they don't get that ability, or at least make the response we do give not worth the effort to them.