The outcome of the war in Ukraine has always been a game of chicken, being which side is willing to escalate to nuclear weapons, and whether the other side may or may not back down. The logic of escalation has always been that no possible gain exceeds the losses caused by a nuclear exchange. The Madman theory ( en.wikipedia.org/wiki/Madman_theory ) is about convincing one’s opponent that is one is not rational, and is willing to use nuclear weapons despite the losses. The threat then, is that Putin, seeing himself politically vulnerable because of his losses, but still powerful enough to command the military to use nuclear weapons, would demonstrate his willingness to use nuclear weapons, even if not directly against a military target, in a demonstration (perhaps in the Black Sea) or an exoatmospheric test.