Does partisan disagreement impact expectations of victory in war? We conjectured it could by degrading military cohesion. We registered two main predictions: (a) soldiers fight less effectively if they observe political parties disagree during a crisis about whether to initiate war and (b) the effects of (a) are amplified when soldiers are affiliated with a dissenting opposition party. With some nuance, we found broad support for these predictions through two preregistered survey experiments that recruited South Korean military cadets and soldiers of appropriate ranks for warfighting. Our novel design estimated effects on the will to perform six essential battlefield tasks given land-battle doctrine, unit structures, and force employment of modern democratic armies. Thirteen exploratory tests yield findings consistent with arguments that military institutions provide nonpartisan socialization, but surprising for research on nationalism, soldier-to-soldier trust, and the psychological and dispositional determinants of military effectiveness. We also introduce and calibrate rifle shooting outcomes for experiments.
Joseph et al. (Tue,) studied this question.