The 'Cominternians' who staffed the Communist International in Moscow from its establishment in 1919 to its dissolution in 1943 led transnational lives and formed a cosmopolitan but closed and privileged world. Full of sympathy, eager to learn, hopeful of emulating Bolshevik success 'at home', they were first-hand witnesses to the difficulties of the young Russian Revolution, before seeing it descend into the terror to which many of them fell victim. This book tells of their experience through these decades, of the encounter between utopian imagination and the real, and how the Party as institution sought to bend subjectivity to its needs, even as they became ever more questionable. Opened some 25 years ago, the Comintern archives provide a surprising wealth of autobiographical materials generated by these militants, and it is on these that this account of political commitment and its vicissitudes is based.