The Revolutionary Left Movement (, MIR) is a Chilean far-left Marxist-Leninist communist party and former urban guerrilla organization founded on 12 October 1965. At its height in 1973, the MIR numbered about 10,000 members and associates.Historical dictionary of terrorism, By Sean Anderson & Stephen Sloan, Page 447, Scarecrow Press, 2009 The group emerged from various student organizations, mainly from University of Concepción, that had originally been active in the youth organization of the Socialist Party. They established a base of support among the trade unions and shantytowns of Concepción, Santiago, and other cities. Andrés Pascal Allende, a nephew of Salvador Allende, president of Chile from 1970 to 1973, was one of its early leaders. Miguel Enríquez was the General Secretary of the party from 1967 until his assassination in 1974 by the DINA.

Although it was involved in military actions and assassinations, particularly during the Resistance to the 1973 Chilean coup d'etat, the MIR states they reject assassination as a tacticMarcello Ferrada de Noli, "Nelson Gutierrez. In memoriam. Notas sobre la Historia del MIR". [English Summary]. Stockholm, 2008. The author put forward a rationale for this condemnation, which would to be based in both ideological and strategic factors. The author also quotes a MIR official document of the epoch "El MIR a los Estudiantes, Obreros y Soldados. Declaración Pública of 16-06-1971" in which MIR confirmed anew to have "categorically" condemned assassinations as the one carried out by the VOP (referring to Edmundo Perez Zujovic fall): "Hemos sido categóricos en condenar las acciones de la VOP, pues éstos han utilizado el atentado personal como método, hoy en Chile" (Pages 14-15) . (see below on the assassination of Edmundo Pérez Zujovic by the VOP).

Before the coup The Sino-Soviet ideological dispute, the Soviet Union's invasion of Czechoslovakia (and other Warsaw Pact etc. events), the presence of the Cuban Revolution in Latin America, and the emergent global student movement partially inspired by the thought Frankfurt School and the New Left (by the time of the early opposition to the Vietnam War) were the main ideological issues that the traditional Chilean left (the Socialist Party and the Communist Party) had to deal with amid their relative political stagnation in the beginning of the 1960s.Historian Julio César Jobet describes how repeated attempts by the traditional Chilean left ("FRAP", a front formed by the Socialist Party of Chile and the Communist Party of Chile) to win the presidential elections of 1958 and 1964 failed. The author mentions as cause, "the sterile alliance of the working class parties with petty-bourgeois democratic parties". The new Popular Unity (Chile) was only able to access government in the elections of 1970. See pages 57-60 in "El Partido Socialista de Chile", Tomo I, Ediciones Prensa Latinoamericana S.A., Chile, 1971.

By the early 60s, amidst a political dominance of the right-wing and center-right wing parties strongly supporting US policies, the traditional left parties' "reformist" doctrine of a non-revolutionary road to socialism began to be questioned by different militant groups within those parties. The questioning for changes and the opposition against such changes resulted in several small groups or factions.Frank Gaudichaud (2013), "Chili 1970-1973. Introduction Générale". Presses Universitaires de Remnes, C. Camilo Fernández Carrozza & Pablo Garrido González (2016). "Progresistas y revolucionarios: el Frente de Acción Popular y la vía Chilena al Socialismo 1956-1967". Izquierdas, 31:71-101, diciembre 2016

The Maoists left the Communist Party and the Socialist Party group of students. At the same time, since World War II, there were some minor Trotskyist formations and minor left-libertarian groups, which also had a discrete ideological influence in the student movement in Santiago and Concepción. The group led by Miguel Enríquez, temporarily allocated in the cell "Espartaco" at the Socialist Party, called itself the "Revolutionary Socialists" faction. It was formed by Miguel and Marco Antonio Enríquez, B. Van Schouwen, Marcello Ferrada de Noli (a left libertarian and then the leader of the socialist cell "Espartaco" in Concepción), and Jorge Gutiérrez.Pedro Naranjo (2004). "Biografía de Miguel Enríquez". CEME. Page 10 and Note 10 When this fraction was finally ousted from the Socialist Party (Senator Ampuero) in February 1964, it continued as an independent fraction until they merged in the organization VRM. There the young socialists met with Trotskyites, most of them twice their age.Eugenia Palieraki (2008). "L'option des armes. Nouvelle gauche révolutionnaire et violence politique au Chili (1965-1970)". English abstract and full text in Spanish. Polis, 2008, N° 19 Mark Ensalaco (2000). "Chile Under Pinochet- Recovering the truth". University of Pennsylvania Press.

When MIR was founded on 12 October 1965 at the locals of an anarchist union in Santiago, less than 100 participated, and all the above ideological tendencies were represented. Revolutionary socialists (by Miguel Enríquez and B. Van Schouwen), former communists (represented by the Maoist Cares), Trotskyists (by Dr. Enrique Sepúlveda and Marco Antonio Enríquez, Miguel Enríquez's brother), left-libertarians or social anarchists (by Marcello Ferrada de Noli), and anarcho-syndicalists (by Clotario Blest). It took some time before the MIR finally could achieve its ultimate identification as a solely Marxist-Leninist political organization, and this was the work of Miguel Enríquez for the two years to come.

The first document approved at MIR foundation congress was the "Tesis Insurreccional", the political-military theses of MIR. The document was written by Miguel Enríquez (Viriato), Marco Antonio Enríquez (Bravo), and Marcello Ferrada de Noli (Atacama),Pedro Alfonso Valdés Navarro (2008) "Elementos teóricos en la formación y desarrollo del MIR durante el periodo 1965-1970". Universidad de Valparaíso, Chile. Tesis de grado. Pages 1-121 all three from Concepción. Two reasons explain this document and its co-authorship: The first is that the group of young students from Concepción led by Miguel Enríquez was the most numerous. The second is that the group from Concepción internally had some different ideological profiles, which were represented in the document written by the co-authors. The differences in ideologies are due to the wide support base it drew from. The MIR in Concepión utilized its grassroots approach by relying on a diverse group of organizations to make up its supporters. Students from the university would hold debates and often be open to hearing others opinions on issues that were at hand. The supporters in Concepción have been highlighted by historian Marian Schlotterbeck in her book Beyond the Vanguard: Every Day Revolutionaries in Allende’s Chile. In her book, she described the structure that was used to organize the sub-groups of the MIR, she said, "delegates would be drawn from the labor federation (CUT), unions, peasants councils, student federations, and pobladores' organizations," pointing towards the diversity of supporters that the movement was able to gather. The successes of this branch at the first People's Assembly was in part owed to the many different speakers from separate organizations and their ability to connect with and mobilize their own supporters. Several tendencies were represented on the Central Committee, but later, the only line that prevailed was the Marxist-Leninist. Both Maoists and Trotskyites abandoned MIR or were ousted by the new Secretariat led by Miguel Enriquez. The few anarchist and left liberal cadres supporting the "tendencia social-humanista" and that remained in the organization, were confined to academic tasks and trusted the ideological polemic with the emergent "Christian Humanism" and old Stalinists.

After the second congress in 1967, MIR considered itself not only a revolutionary vanguard party as established in the 1965 foundation congress, but also clearly advocated a Marxist-Leninist model of revolution in which it would lead the working class to a "dictatorship of the proletariat".

Yet in recent years, some scholars have cast doubt if the MIR was completely uniform ideologically across all its constituents. Dr. Marian Schlotterbeck in her book Beyond the Vanguard: Everyday Revolutionaries in Chile points out differences in party allegiances between national and regional MIR groups. For instance, the Concepción Peoples Assembly on July 27, 1972 saw the Concepción regional MIR directly collaborating with the Popular Unity coalition. The contemporaneous national MIR did not work with the Popular Unity, meaning that the regional party effectively created "a new political alliance that didn't exist at the national level." Moreover, Schlotterbeck also shows how events within the Concepción province attributed to the MIR organization were begun by grassroots actors on their own initiative rather than organized by the party itself, such as the conversion of the private bakery "El Progreso" into the communal bakery "El Pueblo." So, while national party members at Santiago nearly all believed in the Marxist-Leninist style of revolution, the on the ground reality in some cases was distinct with the working class leading the MIR into a socialist revolution rather than the other way around.

The Soviet Invasion of Czechoslovakia, 1968 was a divisive issue for the Chilean left. Whilst the Allende faction of the Socialist Party remained neutral, the far-left militants of this party opposed the Eastern bloc invasion, as did MIR.

In 1969, following the "Osses case", a direct (non-fatal) operation acted by four militants of MIR in Concepción against the right-wing tabloid Noticias de la Tarde, the Christian Democratic Party government used the incident to ban the MIR and begin persecution of its known leaders. The government publicized a national list of 13 young MIR leaders for their capture.Diario "El Mercurio", Santiago de Chile, "A Través de la Historia Terrorista del Movimiento de Izquierda Revolucionaria (MIR)", 25 August 1973. Among them, all between 22 and 26 and with links to the University of Concepción, were Doctors Miguel Enríquez and Bautista van Schouwen, Professor Marcello Ferrada de Noli, medical student Luciano Cruz, sociologist Nelson Gutiérrez, lawyer Juan Saavedra Gorriategy, civil engineer Aníbal Matamala, and economist José Goñi (Goñi later became a Minister of Defense and ambassador of Chile in the USA). Some of them were captured after spectacular operatives coordinated by the central headquarters of the Chilean Political Police in Santiago, tortured, and imprisoned in the Cárcel of Concepción and in Santiago.

On 1 May 1969, fifteen armed MIR guerrillas stormed the Bío-Bío radio station of Concepción and transmitted a discourse urging the people to take up arms and overthrow the current government.Determinants of gross human rights violations by state and state-sponsored actors in Brazil, Uruguay, Chile, and Argentina, 1960-1990, By Wolfgang S. Heinz & Hugo Frühling, Page 423, Martinus Nijhoff Publishers, 1999 On 21 May, a group of local MIR sympathizers took to the streets of Concepción and attacked the branches of 'The City Bank' in the city and the offices of the La Patria newspaper.