“Divided priorities: why and when allies differ over military intervention” by Ronald R. Krebs and Jennifer Spindel is an important piece of research. The authors challenge the validity of the claim that weaker allies value their patrons’ hawkish postures in distant conflicts. This claim, first put forward by Glen Snyder in Deterrence and Defense (1961), reasons that a patron’s limited foreign interventions make allies feel reassured of their own defense commitment with their patron state: if their benefactor is willing to fight for places of trivial intrinsic and strategic importance, it will surely also be willing to fight for them if the necessity arises.
The defining characteristic of modern international politics is unipolarity. Never before has one state achieved such a remarkable lead in economic capacity and military capability. American power today is unrivalled and durable, even after the economic crisis of the last decade. It will be a very long time before another state qualifies as a peer competitor.