In 1996, renowned U.S. defense expert Fred Iklé proposed that the nuclear drama of the past decades had entered its more volatile second act. Soon after, the term "second nuclear age" began to be widely used among nuclear strategists.
Unlike the first age, marked by bipolar competition with the Soviet Union, the main challenge of the second age would come from belligerent regional powers equipped with weapons of mass destruction (WMDs) and ballistic missile technology. However, this era was not thought to last forever-for Professor Colin Gray, even in 1996, wrote the "second nuclear age can be seen as a period of interregnum between irregular cyclical surges in the kind of great power rivalry that organizes many strands in the course of strategic history."