While defeat in a foreign war is a common cause of political and social revolutions, not all wars end in uprisings. When and where does war lead to mass rebellion? I address this question by studying how the exposure to the Russo-Japanese War through military conscription and mobilization affected the number of peasant revolts and industrial workers' strikes during the First Russian Revolution of 1905-07. Using original historical data, I leverage plausibly exogenous variation in military conscription quotas and partial mobilization waves by province-year to show that coercive military service increased citizen grievances and led to unrest. Further examination of the heterogeneous treatment effects suggests that conscription resulted in mass uprisings after the defeat in the war and in the presence of ethnic and religious minorities.