De Leonism, occasionally known as Marxism-Deleonism, is a form of syndicalist Marxism developed by Daniel De Leon . De Leon was an early leader of the first United States socialist political party, the Socialist Labor Party of America . De Leon combined the rising theories of syndicalism in his time with orthodox Marxism. According to De Leonist theory, militant industrial unions (specialized trade unions ) are the vehicle of class struggle. Industrial Unions serving the interests of the proletariat (working class) will bring about the change needed to establish a socialist system. The only way this differs from some currents in anarcho-syndicalism is that, according to De Leonist thinking, a revolutionary political party is also necessary to fight for the proletariat on the political field.