German Communists were among the first to be imprisoned in concentration camps. Their ties to the USSR concerned Hitler, and the Nazi Party was intractably opposed to communism. Rumors of communist violence were spread by the Nazis to justify the Enabling Act of 1933, which gave Hitler his first dictatorial powers. Hermann Göring testified at Nuremberg that Nazi willingness to repress German Communists prompted Hindenburg and the old elite to cooperate with them. Hitler and the Nazis also despised German leftists because of their resistance to Nazi racism. Many German leftist leaders were Jews who had been prominent in the 1919 Spartacist uprising. Hitler referred to Marxism and "Bolshevism" as means for "the international Jew" to undermine "racial purity", stir up class tension and mobilize trade unions against the government and business. When the Nazis occupied a territory, communists, socialists and anarchists were usually among the first to be repressed; this included summary executions. An example is Hitler's Commissar Order, in which he demanded the summary execution of all Soviet troops who were political commissars who offered resistance or were captured in battle.