We estimate the causal impact of military conscription on long-term beliefs and personality traits. To address potential endogeneity concerns, we exploit the conscription lottery in Argentina. We combine administrative data from the conscription lottery with data from a survey we designed on beliefs and personality traits. We find that men who were conscripted are more likely to adopt a military mind-set and that the effect is long lasting. Given the many people who go through military conscription, our results are useful for understanding how personality traits and beliefs are formed for a very salient part of the world's population.