Russia Ukraine war, page-9693

Short answer is that if US or NATO territories are attacked with nuclear weapons, there is a NATO submarine close to the aggressor that would respond in kind. So if Putin nuked Warsaw, Moscow would cease to exist shortly afterwards. Is that what you wanted to know?

But Putin and his military and advisors also DO KNOW it, so that even if Putin in a demented rage decided to do it, you would hope that his generals and advisors would fail to follow his orders and remove him.