When and how did the Nazis decide to murder the Jews under their control?

The exact date of the Nazi policy decision to murder all the Jews is not entirely clear. No written order from Hitler to this effect has been found. Currently there is a consensus among historians, however, that before the outbreak of the war the Nazis did not have a definite plan to murder the Jews of Europe. Rather, the policy that came to be known as the Final Solution, which called for the murder of all Jews, developed during the war itself.

At the time of the German conquest of Poland, in the autumn of 1939, the Nazis crossed the line from earlier forms of discrimination to murder. At this point, sporadic mass killings in the Generalgouvernement alone, the area where most Polish Jews were gathered, resulted in the deaths of at least 7,000 in the last months of 1939. With the invasion of the Soviet Union on June 22, 1941, murderous activities against the Jews were greatly intensified. German armed formations, chief among the special units of the SS known as the Einsatzgruppen, began shooting Jewish males as well as Communist political officers in a mass and systematic fashion.

In early July, the “No. 2” man in the SS, Reinhard Heydrich, was made responsible by Hitler's deputy Hermann Goering for a "Final Solution to the Jewish Question in Europe." In mid-August, when the head of the SS, Heinrich Himmler, visited the newly occupied Soviet areas, it was decided to extend the killing to Jewish women and children. Soon thereafter experiments began on the use of Zyklon-B gas as a means for mass murder. These experiments were conducted in Auschwitz on Soviet prisoners of war. In mid-October the deportation of the Jews from the Reich began, and just a few days later, Jewish emigration from the Reich was forbidden. Also in October, sites were chosen for the extermination camps Chelmno and Belzec. In early December, the first extermination camp, Chelmno, went into operation. There Jews began to be murdered with carbon monoxide gas generated by large diesel engines that pumped gas into gas chambers.

On December 12, it is known that Hitler met with some of his intimate circle and told them that the systematic mass murder which had begun in the Soviet Union would be extended to the Jews of Germany, the last group to be included in the plans for murder. From this meeting we know that the decision to include all Jews in the murder was made before December 12 – most likely during the autumn of 1941. On January 20, 1942, after hundreds of thousands of Jews had already been murdered, Heydrich convened various senior members of the German bureaucracy in what has come to be known as the Wansee Conference to discuss and coordinate the "Final Solution."

It is clear from this series of events that Hitler, Goering, Himmler, Heydrich, and other Nazi leaders were closely involved in the decision-making process which led to the mass murder of the Jews.