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.