The importance of the years of political and social upheaval immediately following the end of the Second World War and coinciding with the beginnings of the Cold War, that is to say, the period from 1944 or 1945 to 1948 or 1949, for the history of Europe (East and West), the Near and Middle East, Asia (Japan, China, South and East Asia), even Africa (certainly South Africa) in the second half of the twentieth century has long been generally recognised. In recent years historians of the United States, which had not, of course, been a theatre of war and which alone among the major belligerents emerged from the Second World War stronger and more prosperous, have begun to focus attention on the political, social and ideological conflict there in the postwar period – and the long term significance for the United States of the basis on which it was resolved. In contrast, except for Argentina, where Perón's rise to power has always attracted the interest of historians, the immediate postwar years in Latin America, which had been relatively untouched by, and had played a relatively minor role in, the Second World War, remain to a large extent neglected. It is our view that these years constituted a critical conjuncture in the political and social history of Latin America just as they did for much of the rest of the world. In a forthcoming collection of case studies, which we are currently editing, the main features of the immediate postwar period in Latin America, and especially the role played by labour and the Left, will be explored in some detail, country by country.1 In this article, somewhat speculative and intentionally polemical, we present the broad outlines of our thesis.