Earlier quoted context omitted.
In some cases, this was because of a single person's brave decision (Vasily Arkhipov prevented Soviet nuclear escalation in response to US aggression in the Cuban Missile Crisis, and Stanislav Petrov prevented it in 1983 when Soviet missile detectors misreported sunlight reflecting from clouds as 5 incoming American ICBMs -- credit to commenter folkrav). In general, though, there's an incentive: Mutually Assured Dest…
Unfortunately and fortunately, MAD and "launch it or lose it" are far-too-simplistic descriptions of the situations facing the decision makers. Unless a side's leaders are very narrow fanatics (vs. mere posturing as such for political benefit), "winning" an all-out nuclear war via first strike is a pretty shitty victory. Whether or not you believe in nuclear winters, the world would be a huge radioactive mess, with e…
1. When a nation perceives a threat as severe and imminent, attitudes harden quickly. This perception can be achieved independently of whether the threat is real. Nuking the other guy first, consequences be damned, could quickly become a very popular policy.
2. I think the "nuclear winter would harm us all" argument depends on how geographically large the target is. It's a strong argument against trying to strike all of Russia, China, or the US, but less strong against, say, the UK or (at the extreme end) Taiwan or Singapore.