Latin America has been one of the less successful arenas for the international communist movement. Until Castro's victory, Iberian America repeatedly proved the graveyard of communist hopes. The explanations given for this failure have been various: inability of Moscow to understand the regional differences in Latin America, Russian unwillingness to risk defeat at the hands of American intervention (as in Guatemala in I954), and a stubborn and unimaginative commitment to the 'legal path' by Latin American communists loath to risk their respectable careers.1 All these explanations have merit, but they should not obscure the question inherent in communist doctrine: how to apply the Marxist-Leninist theory of revolution in greatly varying historical circumstances. When is armed insurrection to be preferred to a patient 'legal' strategy ? The answer has varied according to the changing position of the Soviet Union and the shifting opportunities presented by communist parties and their host countries. Latin America during the I930s offers an interesting example of the communist revolutionary's perennial dilemma. During 1934 the Comintern began to move away from the 'sectarian' attitude adopted in I928 and to ponder seriously the extent to which communist parties should co-operate with the noncommunist left. By 1935 the popular front strategy had emerged as official Comintern policy. Although Latin America hardly occupied the centre of Comintern attentions, it offered challenging theoretical and practical problems.