Back in the years of World War I, a left-wing radical wing of internationalists took shape in the world workers’ and social democratic movement. So, in contrast to the majority of the Second International socialist parties, which supported their countries’ governments, the Bolsheviks’ leader, Vladimir Lenin, put forward the slogan of turning the world imperialist war into a civil war, which was to bring the working class to power. The Bolsheviks only considered acceptable cooperation with left-wing parties that opposed the war. Lenin raised the question of establishing a new International back in 1914. During World War I, the Bolsheviks took part in international socialist conferences in Zimmerwald (1915) and Kienthal (1916) and initiated the formation of the Zimmerwald Left group (an international group of left socialists, which included Vladimir Lenin and Grigory Zinoviev, advocating an organizational break with the parties of the Second International).

As the Bolsheviks came to power in Russia, they had the opportunity to lead the world communist movement and create the International Organization of Communist and Left Social Democratic Parties. On March 2–6, 1919, the Founding (First) Congress of the Communist International (Comintern, III International) was held in Moscow. It was attended by delegates from 35 parties and groups from 21 countries. The Congress adopted a platform proclaiming the beginning of the era of the world proletarian communist revolution. It was declared that the working class “must destroy the rule of capital, make war impossible, erase the borders between states, turn the whole world into a community working for itself, and realize freedom and brotherhood of peoples.” The anticipated result of revolutionary transformations in all countries on the model of Russia would be the formation of the Union of Soviet Socialist Republics of the world.

The Second Congress of the Comintern in July – August 1920, adopted the Charter, according to which it acted as the world party of the proletariat, consisting of national sections. The break with the Social Democratic parties, which advocated a reformist, non-revolutionary path to socialism, was emphasized.

In 1919–1926, Grigory Zinoviev held the post of the Chairman of the Executive Committee of the Communist International, which was the governing authority of the Comintern between congresses. The Comintern Executive Committee distributed appeals and directives, sent its emissaries, and allocated funds for the revolutionary struggle in various countries of the world.