Hahn and his "Einsatzkommando" took part in the arrests and executions carried out as part of "Intelligenzaktion", the Nazi extermination campaign targeting the Polish intelligentsia. Between September and November 1939 Hahn and "Einsatzgruppe I" were involved in the mass-killing of Polish public officials, activists, intellectuals and army officers in the cities of Katowice, Sanok and Podlesie. They also played a leading role in the expulsion of the Jewish population from the town of Dynow and managed their subsequent deportation into Soviet-occupied eastern Poland.