Putin has made thinly veiled threats about using nuclear weapons against those who interfere with Russia’s invasion of Ukraine. The logic of nuclear deterrence suggests that it’s never in the interest of a nuclear power to engage in war with another country possessing nuclear weapons, as that would lead to mutually assured destruction. But preventing nuclear war is not the sole goal of any nuclear power. Putin might well believe that a world without Russia in its rightful position of power is not worth existing. We can’t be sure of what Putin is thinking, or whether his decision making is compromised – all we can do is prepare for the possibility of Russia’s use of nuclear weapons, writes Herbert Lin.