Radymno fell under German occupation, and the "Einsatzgruppe I" entered the town to commit various atrocities against the populace. Officers of the local Polish military unit were among the victims of the large Katyn massacre, which was carried out by the Russians in April–May 1940. During the war, groups of the Organization of Ukrainian Nationalists, which operated in the area, murdered 59 Poles, including 29 killed in the village of Michałówka. Of the estimated 1,200 Jews in Radymno prior to the World War II only a handful survived, many were handed over by the Ukrainian's collaborators to the Germans and their Nazi regime. Some of the Jews were murdered by the Nazis outside the village in September 1939. The story of the Jewish residents of Radymno is documented in Dov Hister book The Power of Survival.