How did the Holocaust start? 

The Holocaust started gradually. Centuries of ingrained theological anti-Judaism led to racial antisemitism, which resulted in the desire to eliminate the Jews from within Christian lands. The exterminationist aspect of the Holocaust started in earnest in 1941, after the German invasion of the Soviet Union, when the Germans instituted the systematic process of murdering all Jews under their jurisdiction first by shooting and then by gassing them.

The Start of the Holocaust

After the invasion of Poland in 1939 the Germans established ghettos in several Polish cities, where Jews were effectively imprisoned. This is how the Holocaust started. Living conditions in the cramped ghettos was appalling, and disease, hunger and overcrowding killed tens of thousands. The Germans deported Jews from all over occupied Europe to these ghettos, modeled after the ghettos the Catholic Church had established all over Europe since the Middle Ages.

With the invasion of the Soviet Union in 1941 the Germans began the systematic extermination of the Jews, the “Final Solution of the Jewish Question”. The Nazis established special mobile killing squads called the Einsatzgruppen which were attached to the German armed forces and whose only purpose was to follow the army into the Soviet Union and murder all Jews and political undesirables in their wake. This they did with unrelenting efficiency, but shooting thousands of men, women and children at close range every day, day after day, took a toll on the German murderers. So, the Germans set up special concentration camps where they could deport millions of Jews and impersonally kill them systematically by cramming hundreds of them at a time into specially constructed gas chambers, and dispose of their bodies in industrial crematoria. At Auschwitz-Birkenau, the largest of the 20,000 German concentration camps, the Germans murdered about 10,000 Jews every day during the campaign to exterminate the Jews of Hungary in 1944. In the end, between disease, starvation, forced labor, the killing squads, the concentration and death camps and the death marches the Germans murdered 6,000,000 Jews.