Yoooo, there were two incidents in which a Soviet service member saved the world by refusing to fire nukes. One was during the Cuban missile crisis. The USA blockaded Cuba in response to the USSR placing nuclear missiles there. A Soviet nuclear-armed submarine went down under a US naval ship. The ship started throwing dummy charges over to scare the submarine to come out. The sub hadn't had any comm with the USSR in days and thought they were under attack. Two of the three officers needed to approve a nuclear torpedo strike argued for the strike. The other, Vasily Arkhipov, declined despite the other officers insisting. Arkhipov was able to convince the other two to not strike and bring the sub up to reconnect comm with Moscow. The immediate conflict eventually ended with no casualties or strikes. Had they fired a nuclear torpedo, it could have led to a nuclear war.
The other was pretty close too. Three weeks before the incident, a Korean airliner full of civilian passengers accidentally flew into prohibited Soviet airspace due to a navigation error. The Soviets thought it was a US spy plane and shot it down, killing everyone on board. Tensions were high af. Three weeks later, Soviet surveillance equipment showed that the USSR was being attacked with 5 nuclear missiles by the US. Stanislav Petrov saw the incoming missiles and decided to not report the info further up the command because he thought there was no way an American first strike would only be five missiles. He waited for confirmation of the missile strike from the ground, which never came. After a while, it was evident that the system had a malfunction. They eventually discovered that a rare coincidence between the Sun, some clouds, and the Soviet satellites resulted in the false alarm. Had Petrov reported the incoming strike, it is quite possible that higher command would have ordered a "counter" nuclear-strike because of their view of the US.
Both of these incidents were scary close to ending the world as we know it. It wouldn't have just destroyed the USA and USSR. Aside from the direct attacks and destruction of infrastructure and institutions in the stated countries, the strikes would have resulted in a nuclear winter and eventual worldwide famine for over a decade.
Damn. Did not expect to read two different stories about Soviet military officers averting nuclear catastrophe in a community where "Tankie" is a slur.
It's insane that one bomb can basically wipe out an entire metropolitan area that spans several counties. I tried dropping the same one on my city to get a more intimate perspective, and holy crap. The people getting 3rd degree burns wouldn't even consider themselves to be in my metropolitan area. They'd be thinking they're entirely somewhere else.
Luckily, no one makes bombs with this high a yield. I think the highest yield of any deployed weapon is ~10% of that Tsar Bomba one. One would still destroy my city, but it wouldn't completely erase it.
So there are layers to the security history of SAC, including a twenty-year period when we had all our Permissive Action Links set to 00000000, on the pretense that not only could we trust any president to be sane, but we could trust any air force officer to be sane as well.
Curiously this has been proven mostly true. Even Ronald Reagan, who believed wholeheartedly the Second Advent was imminent including a nuclear showdown between the US and the USSR in which he would play the role of President of the United States. President candidate Greg Stillson in The Dead Zone by Stephen King (who commands a first strike in a prophetic vision) is inspired by Reagan. Despite Reagan's eagerness to play his very big role in the apocalypse, he wasn't willing to launch a first strike, and despite all his efforts to provoke the Soviets, they wouldn't either.
(In the meantime, as per the Vulcan saying Only Nixon could go to China, Nixon brought back word of Мирное сосуществование or Peaceful Coexistence a Soviet Politburo policy plan that might allow capitalist and communist ideologies to get along more or less, which Carter was pursuing until his term ended. What no-one would know until the collapse of the Soviet Union in the 1990s, the Politburo had long secretly decided to not respond with a retaliatory strike for sake of giving the human species a chance if the unthinkable were ever to occur.)
My ex-roommate had an uncle who was a key turner at a Polaris silo, and every single time he was up for re-evaluation, he promised that nothing, not threats of violence, not acts of god, would drive him to turn that key ever. He was just not going to do it and feel free to write up a reprimand or a transfer. Notoriously (for years) they kept him at his post.
I haven't had my coffee but I'm pretty sure there's a few ethics training that military folks are given. One involving the My Lai massacre and following orders.
I'm sure for nuke launchers, they only want people to push the button.