The Initiation and Termination of Enduring Rivalries: The Impact of Political Shocks

An enduring rivalry is a competition between states that involve six or more militarized disputes between the same two states around 1960 might be associated with the onset of new rivalries.
Political shocks were found to be a modest necessary condition for the initiation and termination of enduring rivalries with the strongest impact from world wars, civil wars and national independence.
Shocks may be exogenous (world wars) or endogenous (regime change). But in their model, they ignore endogenous aspect.
A shock starts a rivalry. Then, in spite of fluctuations the rivalry stays stable until another shock ends the rivalry.
Of the MIDs (Militarized Interstate Disputes), 45% occur in enduring rivalries, and over half of the wars take place between rivals. Territorial changes occurring in an enduring rivalry are also 3 times as likely to involve military conflict.
Major power rivalries are more sensitive to system shocks than their minor power counterparts. Almost half of minor power rivalries end shortly after a civil war.
Rapid changes in the power distribution at the system level do not affect the end of rivalries, perhaps because only a few rivalries existed at the time of the only shock in 19th century.
They find support for the argument that some ongoing rivalries will end as the state in civil war turns its attention and resources to consolidation of power and to domestic problems.
They also suggest Basic Rivalry Level (BRL). Each pair of adversary nation-states has a BRL around which their relations fluctuate.