Anti-Semitism was an integral part of European twentieth-century nationalisms, and Bandera’s Organization of Ukrainian Nationalists was no exception. The OUN conducted terrorist attacks in pre-war Poland, was persecuted by the Soviets after they occupied Eastern Poland in 1939, allied itself with the Nazis after they invaded the Soviet Union in 1941, and slaughtered thousands of Poles and Jews in a drive to “purify” Ukraine.