Reinhard Tristan Eugen Heydrich (German: ( listen); 7 March 1904 – 4 June 1942) was a high-ranking German Nazi official during World War II, and a main architect of the Holocaust. He was an SS-Obergruppenführer und General der Polizei (Senior Group Leader and General of Police) as well as chief of the Reich Main Security Office (including the Gestapo, Kripo, and SD). He was also Stellvertretender Reichsprotektor (Deputy/Acting Reich-Protector) of Bohemia and Moravia. Heydrich served as president of the International Criminal Police Commission (ICPC; later known as Interpol) and chaired the January 1942 Wannsee Conference, which formalised plans for the Final Solution to the Jewish Question—the deportation and genocide of all Jews in German-occupied Europe.
Many historians regard him as the darkest figure within the Nazi elite; Adolf Hitler described him as "the man with the iron heart". He was the founding head of the Sicherheitsdienst (SD), an intelligence organisation charged with seeking out and neutralising resistance to the Nazi Party via arrests, deportations, and murders. He helped organise Kristallnacht, a series of co-ordinated attacks against Jews throughout Nazi Germany and parts of Austria on 9–10 November 1938. The attacks, carried out by SA stormtroopers and civilians, presaged the Holocaust. Upon his arrival in Prague, Heydrich sought to eliminate opposition to the Nazi occupation by suppressing Czech culture and deporting and executing members of the Czech resistance. He was directly responsible for the Einsatzgruppen, the special task forces which travelled in the wake of the German armies and murdered over two million people, including 1.3 million Jews, by mass shooting and gassing.