Heydrich, Reinhard (1904–1942), a German Nazi official. As head of the Reich Security Office (a part of the SS, the Nazi party police), he was responsible for the arrests and executions of many opponents of the Nazi regime. Heydrich was the chairman of the Wannsee Conference, where the Holocaust was planned. He was known as the “Hangman” because of his brutality. In 1941 Heydrich became Reich Protector (governor) of Bohemia and Moravia. He was killed by Czech underground agents; in retaliation, the Nazis put to death hundreds of Czechs and wiped out the village of Lidice.