[tharkun__]

We've been very very close (probably more than once).

https://www.vox.com/2018/9/26/17905796/nuclear-war-1983-stan...

In short: Russian early warning system operator sees 5 minuteman ICBMs coming towards them. He does not have time to go check with someone. If they are to retaliate, he has to just launch now. No such thing as "waiting for the president to decide to launch". He didn't. Turned out reflections of the sunlight off clouds set off their sensors.

[GiorgioG]

It’s worse than that: https://en.m.wikipedia.org/wiki/Dead_Hand

Beyond that, during the Cuban Missile Crisis the US warships harassed Russian subs that (unbeknownst to them) had nuclear torpedos. These subs thought the US ships were trying to sink them, and as a result they nearly launched their nukes as a last resort.

[zaik]

The logic behind this was that a first strike is unplausible to be only 5 missiles. Stanislav Petrov knew a first strike would have involved hundreds of missiles launched at the same time.