Nuclear peace is a theory of international relations that argues that under some circumstances, nuclear weapons can induce stability and decrease the chances of crisis escalation. In particular, nuclear weapons are said to have induced stability during the Cold War since both the United States and the Soviet Union possessed mutual second-strike retaliation capability, which eliminated the possibility of nuclear victory for either side. Proponents of nuclear peace argue that controlled nuclear proliferation may be beneficial for inducing stability. Critics of nuclear peace argue that nuclear proliferation increases the chance of nuclear war and of nuclear material falling into the hands of violent non-state actors that are free from the threat of nuclear retaliation.