The founding of the Comintern in 1919 was historically destined to be an alternative to the reformism of the Second International. Consequently, the Third International, throughout its life, was confronted with the problem of providing a real Left, Leninist critique of European social democracy, the main exponent of reformism. Ironically, however, it is this very meaning of Leninism which right from the beginning became a kind of thorn in the flesh in the Comintern's life. Sharp disagreements, criticisms and counter criticisms centred around the issue of what would be the correct perspective of the leftism couched in the phraseology of Leninism. The years between 1924 and 1934 witnessed the unfolding of various currents and crosscurrents related to this question and the eventual closure of this issue. The period under consideration is unique in the sense that it signified initially a gradual and then a complete break with the “mass line” and the united front strategy adopted by the Third Congress of the Comintern in 1921. In other words, this was the time which witnessed a crystallization of the Comintern's understanding of leftism, climaxed by the advent of the “third period” after the Sixth Congress in 1928.

Historically speaking, the rising curve of leftism in the Comintern during this period ran parallel to the growth of Stalinism in the USSR and the growing dissension within the CPSU(B), spearheaded most forcefully and systematically by Trotsky and subsequently by Bukharin in the late 1920s and early 1930s.