Deter together or deter separately?: time horizons and peacetime alliance cohesion of the US-Japan and US-ROK alliances/ Do Young Lee

What explains the degree of peacetime alliance cohesion? Why do some alliances maintain cohesion regarding common external threats while others do not? I argue that the interaction of allies’ threat-specific time horizons determines whether allies are cohesive or incohesive in deterring common threats. I demonstrate that allies’ behavior towards common threats differs depending on the length of their threat-specific time horizons, which can be categorized as either ‘short’ or ‘long.’ Based on this demonstration, I predict that high alliance cohesion occurs when the lengths of allies’ time horizons are mutually congruent, whereas low alliance cohesion occurs when they are incongruent. To systematically measure allies’ time horizons, I propose a novel typology. To test my argument, I conduct cross-case analyses of peacetime alliance cohesion in the US-Japan and US-ROK alliances over the past two decades in response to the rise of China.