In the turbulent interwar period, the political ‘Left’ was one of the most visible protagonists, with historians continuing to disagree about the role it played in shaping the outcome of the political struggles. Embedded in strong ‘moral narratives’ about the ‘rise of fascism’, the ‘crisis of democracy’, and the nature of the Bolshevik Revolution, the political Left has been vilified or lionized. For the period from the mid-1920s until 1939, both supporters and detractors agree that the Left was on the defensive, internally divided and weakened by the Great Depression and subject to repression by the state, whether democratic, authoritarian, or Stalinist. This chapter argues that the failure narrative should not subsume the vibrant experimentation and rich and contradictory diversity of the Left experience. A portrait emerges of the interwar Left that wrestled with inevitably imperfect and varied solutions to the ‘problem of community life’ in twentieth-century mass society.