Why is the Second World War not followed by a wave of victorious socialist revolutions? This volume examines the strategy and political role of Trotskyists and left-wing socialists worldwide between 1938 and 1948. Drawing on extensive documentation, including numerous previously unpublished primary sources, the author explores the relationship between the wartime policies of these two international currents and the development of class struggle and the partisan movement. Offering a sweeping account that also examines the perspectives of the principal enemies of a workers’ revolution, the book also provides the first general history of the first ten years of the Fourth International.