This issue of Revolutionary History presents for the first time in the English language material on revolutionary Marxism in Poland from the 1920s onwards. Poland was one of the few countires in which the Trotskyist movement managed to establish a substantial working class base in the 1930s. Ludwik Hass shows how the Trotskyists operated in Poland under a harsh military dictatorship, as they suffered harassment not merely from the police, but from the Stalinists of the Communist Party. After Poland was partioned by Stalin and Hitler in 1939, the Trotskyists continued to work clandestinelu under conditions of appaling repression.