In June 1941, Lanz led his division in the invasion of the Soviet Union. On 30 June, his division conquered Lvov. There, the Germans discovered several thousand bodies of prisoners who had been executed by the NKVD, as they could not be evacuated. As the news spread, a large-scale anti-Jewish pogrom broke out, in which the town's Ukrainian population participated, stirred up in part by German and OUN posters and proclamations calling for revenge against the "Jewish Bolshevik murders".