Decisively shaped by the turbulent atmosphere of war, occupation and resistance, the years 1943-1955 gave rise to a most unusual flowering of progressive initiatives in Catholic politics, theology and apostolic missions. Though suffering severe setbacks in the deep freeze of the Cold War politics, mid-Century European Left Catholicism was not without influence in the subsequent emergence of Latin Americam Liberation Theology and the deliberations of the Vatican II. This volume constitutes the first attempt to analyse the phenomenon of Western European Left Catholicism from a comparative and transnational perspective.