The Spectre of War looks at a subject we thought we knew?the roots of the Second World War?and upends our assumptions with a masterful new interpretation. Looking beyond traditional explanations based on diplomatic failures or military might, Jonathan Haslam explores the neglected thread connecting them all: the fear of Communism prevalent across continents during the interwar period. Marshalling an array of archival sources, including records from the Communist International, Haslam transforms our understanding of the deep-seated origins of World War II, its conflicts, and its legacy. Illuminating ideological differences in the decades before World War II, and the continuous role of pre- and postwar Communism, The Spectre of War provides unprecedented context for one of the most momentous calamities of the twentieth century.