From Wikipedia

A World At War

The Final Solution

In a February 26, 1942, letter to German diplomat Martin Luther, Reinhard Heydrich follows up on the Wannsee Conference by asking Luther for administrative assistance in the implementation of the "Endlösung der Judenfrage" (Final Solution to the Jewish Question). English translation

The Final Solution (German: Die Endlösung) was Nazi Germany's plan and execution of the systematic genocide of European Jews during World War II, resulting in the final, most deadly phase of the Holocaust. Heinrich Himmler was the chief architect of the plan, and the German Nazi leader Adolf Hitler termed it: "the final solution of the Jewish question" ("die Endlösung der Judenfrage").

Many historians view the Kristallnacht (Night of broken glass) as the genesis of The Final Solution as this event was triggered by the assassination of Ernst vom Rath by a 17-year-old Jewish youth.

Mass killings of about one million Jews occurred before the plans of the Final Solution were fully implemented in 1942, but it was only with the decision to eradicate the entire Jewish population that the extermination camps were built and industrialized mass slaughter of Jews began in earnest. This decision to systematically kill the Jews of Europe was made either by the time of or at the Wannsee conference, which took place in Berlin, in the Wannsee Villa on January 20, 1942. The conference was chaired by Reinhard Heydrich. He was acting under the authority given to him by Reichsmarshall Göring in a letter dated July 31, 1941. Göring instructed Heydrich to devise "...the solution of the Jewish problem..." During the conference, there was a discussion held by the group of German Nazi officials how best to handle the "Final Solution of the Jewish Question". A surviving copy of the minutes of this meeting was found by the Allies in 1947, too late to serve as evidence during the first Nuremberg Trials.

By the summer of 1942, Operation Reinhard began the systematic extermination of the Jews, although hundreds of thousands already had been killed by death squads and in mass pogroms. In Heinrich Himmler's speech at the Posen Conference of October 6, 1943, Himmler, for the first time, clearly elucidated to all assembled leaders of the Reich to what the "Final Solution" referred.