There is a piece in today's NYT about nuclear submarines, arguing that they are no longer necessary. The idea is that our enemies are not nuclear states but non-state actors against which nuclear deterrence will not work. there is something to this--that ballistic missiles in nuclear powered subs are not going to impact the calculations of a Bin Laden. But, in the debate about new wars versus the wars we are fighting, we do have to keep in mind that there are good reasons why we are not fighting against major powers. And part of that answer is, indeed, deterrence. Nuclear subs are a big part of that since these subs are much more survivable in a first strike than land-based missiles. This means that the key element of deterrence--being able to outlast a first strike and thus making such a strike relatively ineffectiveness--is in the hands of the "squids" (the submariners).
I have far less faith in the future intentions of Russia and of China than the authors of the piece. And I have far less faith that nuclear weapons will not be used as a bargaining tool down the road. Having a secure means to retaliate makes it very hard for potential adversaries to imagine nuclear war with the US. The reason we are fighting the wars of today, asymmetric wars with insurgencies rather than conventional or nuclear wars is that these are the only kinds of wars that folks can win against the US.
We do need to make wise and hard decisions about what to invest in--how many carriers do we need? Do we need manned bombers in an age of drones? Do we need more or better artillery if we cannot have lots of the best? But nuclear subs are here to stay as long as there are other countries out there that have the ability to hit land based missiles. Perhaps we need to go to smaller, cheaper nuclear subs rather than having big boomers. But no subs ain't going to happen.