He was a member of the National Socialist German Worker's Party and later a high-ranking leader of the Schutzstaffel. As an associate of Adolf Eichmann, he had a leading role in Operation Reinhard, which saw the murder of over one million mostly Polish Jews during the Holocaust in Nazi extermination camps Majdanek, Treblinka, Sobibór and Bełżec.[5][6][7] Historian Michael Allen described him as "the vilest individual in the vilest organization ever known".[5]