We study empirically how past exposure to conflict in origin countries makes migrants more violent prone in their host country, focusing on asylum seekers in Switzerland. We exploit a novel and unique dataset on all crimes reported in Switzerland by nationalities of perpetrators and victims over 2009-2012. Our baseline result is that cohorts exposed to civil conflicts/mass killings during childhood are 40 percent more prone to violent crimes than the average cohort. We exploit cross-region heterogeneity in public policies within Switzerland to document which integration policies are able to mitigate the detrimental effect of past conflict exposure on violent criminality.