I've always been interested in nuke sub vs conventional sub tatics and theory. True, a lot of people state that "this conventional sub" evaded "some naval group", but I'm pretty skeptical (the Mississippi? Say what?
) . In war exercise conditions, with rules and boundaries, conventional subs look viable. But in general enagements, those capabilities would be stretched. I've talked to a few naval people, and they coyly suggest tactics that would make any non-nuke sub null and void, a nonfactor. Even with 2 week AIP capability, the diesel sub is limited in speed and range. And if the US were to engage a country in war, those subs would be tracked and targeted pretty quickly. They have to snorkel sometime and when the do, they aren't silent--they would be taken out by combined forces.
Of course, US sub officers and captains I've talked with will be biased toward their branch of the service. Even so, I spent an hour discussing everything I could think of regarding sub tactics and capabilities with the Captain of the Texas, and the XO and PCO, among others. I just don't see a diesel sub posing a threat of any kind to a Virginia class except in very limited, special circumstances. And they made it clear they have options to avoid those type of situations.