The horrors of the extermination camps, such as Auschwitz-Birkenau, are what most people primarily associate with the Holocaust. Yet the attempted liquidation of European Jewry began with mass shootings outside the camps, on the Eastern Front, after the Nazi invasion of the USSR in June 1941.
Mobile SS killing squads, called Einsatzgruppen, followed the German military’s rapid advance across today's Belarus, Ukraine, and the Baltic states. Initially killing political opponents such as communists, they were soon massacring entire Jewish communities.
Generally Jews in a town or city were marched to pits outside the settlement, where they were systematically shot. The most notorious of these atrocities was at Babi Yar, on the edge of Kiev (Ukraine). The Nazis ordered Jews in Kiev to assemble on 29 September 1941. In just two days over 33,000 people were marched to a ravine outside the city where they were murdered. Over the following months other groups such as Red Army soldiers, civilians and Roma were massacred in a similar fashion – it is estimated that around 100,000 people were murdered at this single site.
In some areas, particularly Lithuania and western Ukraine, local nationalist collaborators assisted with or carried out the shooting of Jewish populations. Historic, widespread and virulent local anti-semitism was accentuated by propaganda which linked the Soviet occupation (from 1939-41) with Jewish communists.
More than one million Jews had been murdered by mobile killing squads by the end of 1941. Nearly all of the 200,000 Jews in Lithuania were killed in this way.
SS leaders began to become concerned that the scale of the slaughter their men were carrying out could affect their mental health – so began experimenting with alternative methods of killing. Vans were adapted which pumped their interiors full of carbon monoxide. Killing by gas had been pioneered by the Nazi killing of severely disabled people between 1939 and 1940.