A century ago the Communist International held its first Congress in the context of historical events of great content and complexity: the end of the First War, the Great October Socialist Revolution, and the German Revolution. Those who attended the convening of the International Communist Conference had years of confrontation with opportunism, first within the Second International and then against its anti-worker and anti-Marxist drift; confrontation that began in the field of theory and that passed to the political scene in a context of sharpening of international class struggle and in each country with the First World War, an imperialist war.
The Communist International began its gestation in the debates in defence of Marxism against the distortions of Bernstein, in the famous controversy between reform and revolution, that is, in the ideological front against revisionism, waged not only within the German Social Democratic Party but in all parties. It is worth remembering that opportunism theorists grotesquely deformed the revolutionary ideology of the working class, in a permanent and methodical attack: hiding the texts of Marx and Engels, or mutilating them, while erecting a theory away from the tasks for the overthrow of capitalism. The communist parties and groups that rebelled against the opportunist direction of the Second International understood very well the need to rescue Marxist theory, and for that reason they gave themselves to the tireless task of publishing the classic works and to making them known, such as the correspondence, the unpublished manuscripts, which showed that the general meaning of Marx and Engels was the proletarian Revolution. They also understood that opportunism sought to make Marxism a dogma as a way to debase it, and that it was necessary to enrich it in terms of new economic and social developments, including the passage of capitalism from free competition to monopolies, which led them to acquire a leading role in the plane of theory to have an arsenal of heavy calibre in the events to come, that is, the beginning of a new era of social revolution.
Such a prognosis, due to the great revolutionary theoretical effort of Lenin and the Bolsheviks, and the Marxist currents of other countries, is what allowed the bold approach of a new international despite going against the flow, even when they were a minority  even though social-chauvinism and social patriotism seemed to be hegemonic or even absolute in the years 1914-1918.
It is that one of the abandoned elements of Marxist theory by opportunism is that of proletarian internationalism. Abandoned and also betrayed, as evidenced by the conduct of the Second International in decomposition, in the First World War. Proletarian internationalism not only conceived as fraternity among workers in all countries, as the necessary actions of solidarity and common action, but also as a framework for political elaboration, that is, for the design of a unified revolutionary strategy.
In the Letter to the workers of Europe and America dated January 21, 1919, Lenin describes very well that the political reality that underpins the existence of the Communist International, even before its founding Congress, the First Congress, is the rupture with the Second International of the Bolshevik Party, strengthened by the decision of the German Spartacists to form the Communist Party of Germany; and together with them the proletarian communist detachments of Latvia, Finland, Poland, Austria, Hungary, the Netherlands.
All of them positioned themselves against the platform consisting of “The defence of class collaboration, the abandonment of the idea of socialist revolution and revolutionary methods of struggle, adaptation to bourgeois nationalism, the forgetting of the historically transitory borders of the nationality or of the homeland, the fetishism of bourgeois legality, the renunciation of the class point of view and the class struggle for fear that the 'broad popular masses' will depart (read the petty bourgeoisie): such are undoubtedly the ideological foundations of opportunism” 
The fight against opportunism, revisionism and reformism, permanent and without concessions to rescue Marxism, restoring its characteristics of revolutionary ideology of the proletariat, was a fundamental premise for the emergence of the Third International.
The decision to keep the flag of proletarian internationalism high in the face of its abandonment by the majority of the Second International, was another fundamental premise. The pressures were very strong and literally had to be against the current. It was a crime of the opportunists to endorse the war and take the workers to the carnage.
Of course, the example that in defence of principles we should not fear to be in minority is of great validity.
Lenin also emphasizes that another important characteristic of the Third International is to put into practice, after the Paris Commune, the dictatorship of the proletariat, with the Great Socialist Revolution and Soviet power.
Once the Communist International has been formed, its presence and activity qualitatively nourished the international class struggle of the proletariat. The First International, and the Second International, despite their great efforts, did not have the global impact that the Communist International did.
For the first time the dissemination of the ideas of scientific socialism, enriched as Marxism-Leninism, was universalized. An extraordinary effort to translate and print the classics, organizing their distribution, even in conditions of secrecy throughout the Continents, in all languages and in a good part of the dialects. Millions of workers have therefore had contact with communist ideas.
On all continents and in most countries when the sections of the Communist International were formed, the working class had its vanguard detachment, its political party, the communist party. In some countries, for example those in Europe, there were parties that were the result of the struggle between opportunists and revolutionaries within the framework of the organizations of the Second International, but in Latin America, Asia and Africa, at least, the proletariat counted for the first time with its class party. Over the course of a century the importance of this contribution of the Third International is demonstrated, since the workers with their Chiefs of Staff have carried out revolutionary processes, have organized themselves better and have accumulated an experience for their historical objective.
In addition, such parties resulting from the work of the COMINTERN, depending on the 21 Conditions to enter it, were forged as new-type parties, based on the Leninist theory of organization, which meant a gigantic advance in relation to existing forms of the social democratic parties. As the backbone of the communist parties, thousands of militants were trained as cadres at the Leninist International School.
In the Congresses and Plenary sessions, as well as in all its commissions and organizations, the III International carried out a constant study of the class struggle, of the economic situation and its tendencies, of the reactionary policies, of the political actions of the revolutionaries in each country, of the socialist construction and its difficulties, of the inter-imperialist contradictions, of the antagonism between the exploited and the exploiters, between the oppressed and the oppressors, and designed the strategy and tactics, the slogans. A world brain of the working class worked in the fight against capital.
It should not surprise us that the class enemy attacks the Communist International, but it is serious that some leaders and cadres in the communist movement, including the contemporary, assume the false idea that the orientations were taken in a centre and were alien to reality, or plagued by Eurocentrism. It is possible today to discuss in particular the elaborations of the COMINTERN and to verify the seriousness and foundation of their positions. Under no circumstances should we tolerate slander that seeks to caricature the elaboration of common positions, the elaboration of a unified revolutionary strategy, in the way that the Communist International did in its existence, but also the need that exists for it, and not only today, but in the past years and decades that followed the dissolution of the COMINTERN.
Studying the materials of the COMINTERN, the Magazine The Communist International, The International Correspondence, the drafts of agreement of the Executive Committee and of the Plenary, Expanded Plenary and Commissions by region, we will appreciate a deep discussion and the modification of points of view according to the changing reality of the class struggle, as well as the constant adaptation of the orientations. The versions of history of the III International that present it as distant from the events of each of its sections are false.
The workers and communist movement in Mexico took a leap in quality by receiving the enrichment of their perceptions, with the discussions, orientations and advice of the Third International, quickly leaving behind the burden of apoliticism, abstentionism, sectarianism, and other deviations that had cemented the anarchism that took root in the last quarter of the 19th century among the Mexican working class.
The working class of Mexico will forever have a debt with the contribution of the Communist International for the formation of its revolutionary political party, the Communist Party.
 Lenin writes in 1914: “The Second International fulfilled its mission, carrying out a useful preparatory work for the prior organization of the proletarian masses within the long period 'pacifies' the cruellest capitalist slavery and the fastest progress capitalist of the last third of the nineteenth century and the beginning of the twentieth. The Third International has before it the task of organizing the forces of the proletariat for the revolutionary offensive against capitalist governments, for the civil war against the bourgeoisie of all countries for political power and for the victory of socialism. ”
 Lenin, Vladimir Ilich; The situation and tasks of the Socialist International; Complete Works Volume 41; Progress Editorial, Moscow