In 1941, the Germans decided on the Final Solution of the Jewish Question-the extermination of all Jews in Europe wherever they were. Aktion Reinhard was the German code name for the murder of the largest concentration of Jews, those in the General Government. It was named for Reinhard Heydrich, the Chief of the Reich Security Main Office (RSHA) and of the Security Police, who was assassinated by Czech partisans in June 1942. It used carbon monoxide gas in specially built extermination camps. Preparations began in the fall of 1941; operations, the following spring. By the end of 1942, most Jews in the General Government, estimated at 2,284,000 by the Nazis in January, were dead. Some 300,000 were spared for work, and the Germans killed most of them in 1943.