Trotskyism is the theory of Marxism as advocated by Leon Trotsky. Trotsky identified as an orthodox Marxist and Bolshevik-Leninist, and supported founding a vanguard party of the working-class, 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 the idea of Socialism in One Country. Trotskyists also criticise the bureaucracy that developed in the USSR under Stalin.