The shootings in Russia proper culminated in the Battalion 45 massacre of 33,000 Jews at Babi Yar.[14] The Order Police battalions became indispensable in the implementation of the Final Solution after the Wannsee Conference of 1942.[15] They rounded up tens of thousands of Nazi ghetto inmates for deportations to extermination camps during the liquidation of the Jewish ghettos in German-occupied Poland, but also participated themselves in the killing of Polish Jews along with the Holocaust executioners known as Trawnikis.[16] During Operation Reinhard mass murders were committed by Battalion 101 against women, children and the elderly in various locations including forced-labour camps and subcamps, most notably during the Aktion Erntefest of 1943, the single largest German massacre of Jews in the entire war, with 42,000 victims shot in the execution pits over the bodies of others.[17]