Research on remedies for affective polarization has primarily focused on psychological interventions, and limited studies consider how state institutions might depolarize voters. I argue that compulsory military service—a central state institution—can depolarize voters because it prevents early partisan sorting and increases the likelihood of contact between partisans during their impressionable years. Leveraging the staggered abolition of mandatory conscription laws in fifteen European countries and employing a regression discontinuity design, I show that men exempt from mandatory conscription report higher levels of affective polarization than men who were subject to mass conscription. This effect is mainly driven by partisan parochialism among men exempt from service and is unrelated to ideological change. My findings emphasize the potential depolarizing effects of state institutions and illustrate how the abolition of mandatory service contributed to intensified patterns of affective polarization in Europe, contributing to the literature on the institutional origins of affective polarization.