Any idiot can say that in 2017.
In 1967 you'd have to special kind of idiot to discount it as ineffective.
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.