We study the long-term impact of compulsory military service, a powerful nation building tool, on attitudes toward immigrants. Using a regression discontinuity design, we compare cohorts of men required to serve with those exempted due to suspension of compulsory service in 21 European countries. We find that conscripts exhibit more negative attitudes towards immigrants, whereas this is not true for women in the same birth cohorts. The impact is more pronounced in countries with high levels of immigration, and when the military service was done during a left-wing government, and hence provided a stronger change in narrative during a crucial formative period.