The Communist Party USA and its allies played an important role in the United States labor movement, particularly in the 1930s and 1940s, but never succeeded, with rare exceptions, either in bringing the labor movement around to its agenda of fighting for socialism and full workers' control over industry, or in converting their influence in any particular union into membership gains for the Party. The CP has had only negligible influence in labor since its supporters' defeat in internal union political battles in the aftermath of World War II and the CIO's expulsion of the unions in which they held the most influence in 1950. After the expulsion of the Communists, organized labor in the United States began a steady decline. Historians disagree why the union movement never formed a labor party and why American workers have never embraced socialist parties in any numbers in the last ninety years. Some have argued that a strain of American exceptionalism made U.S. workers resistant to parties that emphasized class struggle; others have attributed the left's failure to its own successes in building strong unions, but at the cost of downplaying its own political and social agendas for the sake of unity or short-term gains. Others take just the opposite position: that the left lost its power to lead the labor movement by its ideological zig-zags. The CP's history within the labor movement can support all of these theses. CPUSA's founding and early years The Communist Party of the USA was founded in 1919, out of two groups who broke from the Socialist Party of America when it refused to join the Comintern. The original core of the CP believed that the triumph of the Bolshevik Revolution in Russia meant that the revolution was at hand in the West as well. The CP's initial attitude towards unions reflected that millenarian view. At the time of its founding, according to a leader of the party, "it would have been difficult to gather a half dozen delegates who knew anything about the trade union movement." The Party also became a largely clandestine organization during the immediate post-war years, as the Palmer Raids led to the arrest and deportation of thousands of Party members. The CP at that time looked on the American Federation of Labor as an enemy to be destroyed in order to eliminate the temptations of reformism rather than revolution. They also looked