A well-known example is the "Cold War mindset" prevalent in both the U.S. and USSR, which included absolute trust in two-player game theory, in the integrity of command chain, in control of nuclear materials, and in the mutual assured destruction of both in the case of war. Although most consider that this mindset usefully served to prevent an attack by either country, the assumptions underlying deterrence theory have made assessments of the efficacy of the Cold War mindset a matter of some controversy.