ABSTRACT
Opportunistic aggression commonly means the use of force by a challenger when its enemy is already fighting another war. The logic underpinning this danger is straightforward: if deterrence is a function of the perceived capability and perceived willingness of a defender to uphold the status quo, then involvement in a confrontation with one adversary raises the risk of deterrence failure vis-a-vis another. Opportunistic aggression seems to be a particular bane of global maritime powers. These states often face multiple rivals and have a variety of economic interests and security commitments across multiple regions. The prospect of opportunistic aggression has also created recurring dilemmas for the United States. From the late 1940s through the early 1970s, Washington faced challenges from both the Soviet Union and the People’s Republic of China. Opportunistic aggression has not been a rare or trivial occurrence. In fact, it has been the cause of important wars and the source of serious great-power defeats.
