OTOH, relying on ICMB's is contingent on enough people at SAC being sober, which may not be a safe bet.
A first strike can target ICBM launch facilities and effectively neutralize them, meaning those birds either fly when the balloon goes up or they don't fly at all. SSBNs have to be hunted down and destroyed individually. This provides a retaliation capability that cannot easily be destroyed by a massive first strike. They are "second strike" in the sense that they will be available to respond to any nuclear attack, no matter how overwhelming, thus ensuring MAD remains an effective deterrent to nuclear weapons use.
Their missiles don't have the range to hit launch sites that are far inland in North America or Eurasia. Even if they did the missiles would be vulnerable to anti defence. Additionally they are slow moving, which is very undesirable in first strikes.
However they can get really close to major population centers near the oceans and kill millions. Thus second-strike forces are supposed to act as deterrence. Area denial can make them much less effective if combined with proper air defence to take down the missiles.
You're severely underestimating the range of SLBMs. The Russian RSM-56 can cover the entire continental US from both Saint Petersburg and Vladivostok.
This is just wrong. We're talking about ballistic missiles here, not cruise missiles. There isn't a spot on the face of the earth that can't be nuked by a sub from a safe distance.
>Even if they did the missiles would be vulnerable to anti defence.
Also mostly wrong. Only a handful of countries have any defense at all against an IRBM, those defenses only cover a tiny portion of their respective territory, and are both unreliable and relatively easily defeated.
>Additionally they are slow moving, which is very undesirable in first strikes.
Why? If I launch a missile hundreds of miles from enemy ships they're not going to find me. The only thing I have to worry about is a nuclear response, which is a hazard for any platform conducting a first strike.
>However they can get really close to major population centers near the oceans and kill millions.
If by "close" you mean 4000 miles. I guess it's a relative term.
>Area denial can make them much less effective if combined with proper air defence to take down the missiles.
Air defense that wasn't specifically designed to take down ballistic missiles won't have any effect at all.
You're confusing ballistic missiles with cruise missiles. The former are an order of magnitude more difficult to deal with from a planning perspective.
Right but their survivability is contingent upon their not being detected.