Presumably that the risk of nuclear strike was higher

In 1967 US had something like 30,000 nuclear warheads deployed and USSR had 6,o00. Today both countries have around 1,500. Both countries had bombers with nuclear payload continuously up in the air. The risk was much bigger then.

[1] https://www.energy.gov/nnsa/transparency-us-nuclear-weapons-... [2] https://en.wikipedia.org/wiki/Historical_nuclear_weapons_sto...

The bulk of the risk wouldn't really scale with number of warheads though would it? I was thinking it is more of a binary. There is some number of warheads that is enough.

The experience in the Cuban Missile crisis suggests that the number deployed on submarines is probably more of a concern when it comes to miscalculation than the total. And for deliberate attacks the militaries have probably calculated that the number currently deployed is reasonable to wipe out a major power.

The risk of an accident or otherwise unintentional initiation goes up with the number of warheads deployed.

https://en.wikipedia.org/wiki/Soviet_submarine_B-59#Nuclear_...

(or of course Dr Strangelove)