When Do Militaries Fight Battles Together?

Why, and under what conditions, do members of wartime coalitions decide to fight together on the battlefield? We argue that belligerents’ shared stakes and logistical capacity condition the formation of battlefield coalitions. When potential battlefield coalition members regard fighting together in a particular looming combat operation as high stakes and can logistically support that specific effort, they are especially likely to form such a group; when one or more do not regard the combined operation as high stakes, and they cannot muster and sustain the necessary forces, they are almost certain not to try. The likelihood of formation declines when one or both conditions are absent, with logistical capacity more conducive to the creation of battlefield coalitions. We assess our claim by examining of two Allied attempts to form a battlefield coalition during the Burma Campaign in World War II: Operation Anakim, which the Allies abandoned, and a strike at Myitkyina, which the Allies carried out.