We explore the effect of military fatalities from World War I on female labor participation in post-war France. We build a unique dataset containing individual level information for all 1.3 million fallen soldiers, and find that the tightness of the marriage market along with negative income shocks generated by the scarcity of men induced many young single women and older widows to enter the labor force permanently after the war, especially in the industrial sector. These findings are robust to alternative empirical strategies, including an instrumental variables strategy based on idiosyncrasies generated by the recruitment process of the army. (JEL J12, J16, J22, N34)