Is Mutual Assured Disposal a Deterrent?

I think the idea, the idea of mutual ist destruction, is born out of a lack of understanding of human, human behaviour and nature. Because of that doctrine, and it's held for so long, why nobody has launched a nuclear war against anybody else? It would lead to that kind of situatiti where fere nobody wins and everyone loses. The us could use surreptitious methods to wipe out russia. They're not doing anything that we know of. Yes, there's low scale stuff like arain slum down or somethingunding or anding. So i'm not sure a a safe example that, say, we you hack the the water supply,