The United States had a monopoly of nuclear weaponry only a few years before other nations challenged it, but from 1949 until roughly the 1990s deterrence theory worked—nations knew that if they used the awesome bomb they were likely to be devastated in the riposte. Despite such examples of brinkmanship as the Cuban missile crisis and numerous threats of nuclear annihilation against non-nuclear powers, by and large the few nations that possessed the bomb concluded that nuclear war was not worth its horrendous risks. Today, by contrast, weapons of mass destruction or precision and power are within the capacity of dozens of nations either to produce or purchase. With the multiplicity of weapons now available, deterrence theory is increasingly irrelevant and the equations of military power that existed in the period after World War Two no longer hold.