Of course if the US hadn't been experiencing so much political upheaval, they might have tried responding in kind.
The global nuclear arsenal is still over 2500 MT, I bet :(
The crazy bastards.
It was purely a dick measuring contest at that point.
Why is that not feasible? If they could get it on a submarine they could detonate in most of the worlds major cities.
All in all, you're mostly likely to nuke the nearby ocean, rendering it mostly a radiological/environmental weapon. When you consider that you can far more easily launch a combined 100MT in smaller payloads, with a higher resulting degree of destruction than a single 100MT warhead...
I'm not arguing effectiveness. I was arguing against the "not under water" bit, after the person you responded to suggested a sub over a ship.
So, a sub 1,000 miles from shore can hit you faster than you can get out of the blast range when you include a modest detection > reaction delay unless your sitting in an airport. It's vaguely possible you could get into a bunker in that time period, but unless you sleep in a bunker even that's not really viable.
However, by setting up things to respond in the event of a nuclear attack it does not really matter if you take out DC / Moscow as the other subs can respond anyway.
Any idiot can say that in 2017.
In 1967 you'd have to special kind of idiot to discount it as ineffective.