Trotskyism (from 1917)
Trotskyism was initiated by the Russian revolutionary Leon Trotsky, who contributed to the development of Marxist debates by distancing himself from Stalin, on the basis of a critique of the development of bureaucracy in the Soviet Union, while continuing to endorse Lenin. Trotskyism – the term has sometimes been used polemically, to denounce positions that deviated from Moscow's positions – is committed to the international and "permanent" character of revolution.
One key text is The Revolution Betrayed: What is the Soviet Union and Where is it Going?, published by Trotsky in 1936. Comprehensive anthologies of other texts by Trotsky can be found, among other places, at the Marxist Internet Archive, on the website Stimmen der Proletararischen Revolution ("Voices of the Proletarian Revolution") and at the Trotsky Archive, whose website is however no longer updated. There is also a rare audio document of a speech of Trotsky held in German in 1932.
Ernest Mandel, Michel Pablo and Tony Cliff are considered important exponents of Western European Trotskyism since World War Two. Texts can be found at the Pablo Internet Archive, the Marxists Internet Archive (on Cliff) and the Ernst Mandel Internet Archive, among other places.
Today, there are numerous Trotskyist organisations and associations dispersed around the world. They are mainly concerned with political and strategic/tactical issues, pursue "revolutionary Marxism" and continue to be committed to the working class as a "revolutionary subject." The degree of fragmentation that characterises Trotskyism can be seen from a list of Trotskyist parties (in 2005) and Wikipedia's overview of Trotskist organisations.