of Norman Thomas and his associates remaining in the Socialist Party. As early as 1938, Thomas had acknowledged that a number of issues had been involved in the split which led to the formation of the rival SDF, including "organizational policy, the effort to make the party inclusive of all socialist elements not bound by communist discipline; a feeling of dissatisfaction with social democratic tactics which had failed in Germany" as well as "the socialist estimate of Russia; and the possibility of cooperation with communists on certain specific matters." Still, he held that "those of us who believe that an inclusive socialist party is desirable, and ought to be possible, hope that the growing friendliness of socialist groups will bring about not only joint action but ultimately a satisfactory reunion on the basis of sufficient agreement for harmonious support of a socialist program." Following directions from the Soviet Union, the Communist Party USA (CPUSA) and its members were active in the Civil Rights Movement for African Americans. Following Stalin's "theory of nationalism," the CPUSA once favored the creation of a separate "nation" for negroes to be located in the American Southeast. In 1941, after Germany invaded the Soviet Union, Stalin ordered the CPUSA to abandon civil rights work and focus supporting American entry into World War II. Disillusioned, Bayard Rustin began working with members of the Socialist Party USA (SPUSA) of Norman Thomas, particularly A. Philip Randolph, the head of the Brotherhood of Sleeping Car Porters. The Socialist Party and the SDF merged to form the Socialist Party–Social Democratic Federation (SP–SDF) in 1957. A small group of holdouts refused to reunify, establishing a new organization called the Democratic Socialist Federation (DSF). When the Soviet Union led an invasion of Hungary in 1956, half of the members of communist parties around the world quit and in the United States half did and many joined the Socialist Party. Frank Zeidler was an American socialist politician and mayor of Milwaukee, Wisconsin, serving three terms from April 20, 1948, to April 18, 1960. He was the most recent socialist mayor of any major American city. Zeidler was Milwaukee's third socialist mayor after Emil Seidel (1910–1912) and Daniel Hoan (1916–1940), making Milwaukee the largest American city to elect three socialists to its highest office. In 1958, the SPUSA welcomed former members of the Independent Socialist League (ISL), which before its 1956 dissolution had been led