Hitler ordered the German Army to enter Prague on 15 March 1939, and from Prague Castle proclaimed Bohemia and Moravia a German protectorate. For most of its history, Prague had been a multi-ethnic city with important Czech, German and (mostly native German-speaking) Jewish populations. From 1939, when the country was occupied by Nazi Germany, Hitler took over Prague Castle. During the Second World War, most Jews were deported and killed by the Germans. In 1942, Prague was witness to the assassination of one of the most powerful men in Nazi Germany—Reinhard Heydrich—during Operation Anthropoid, accomplished by Czechoslovak national heroes Jozef Gabčík and Jan Kubiš. Hitler ordered bloody reprisals.