Trotskyism is the political ideology and branch of Marxism developed by Russian revolutionary Leon Trotsky and by some other members of the Left Opposition and Fourth International. Trotsky self-identified as an orthodox Marxist, a revolutionary Marxist, and Bolshevik–Leninist, a follower of Marx, Engels, and of 3L: Lenin, Karl Liebknecht, Rosa Luxemburg. He supported founding a vanguard party of the proletariat, proletarian internationalism, and a dictatorship of the proletariat based on working class self-emancipation and mass democracy. Trotskyists are critical of Stalinism as they oppose Joseph Stalin's theory of socialism in one country in favor of Trotsky's theory of permanent revolution. Trotskyists also criticize the bureaucracy that developed in the Soviet Union under Stalin.