Question: Esther Norma Arrostito (January 17, 1940 – January 15, 1978) was an Argentine political activist and leftist militant, initially close to communist ideology, In 1970, she became one of the founders of the peronist revolutionary movement of which organization, along with Fernando Abal Medina, what was an Argentine leftist terrorist and urban guerrilla group, active during the 1960s and 1970s?
Context: Juliet Caroline Belmas was a Canadian anarchist activist, and the youngest of those involved in acts of eco-terrorism and militant direct action with the urban guerrilla group Direct Action (organization) whom the media dubbed the Squamish Five in the 1980s. Esther Norma Arrostito (January 17, 1940 – January 15, 1978) was an Argentine political activist and leftist militant, initially close to communist ideology.  In 1970, she became one of the founders of the peronist revolutionary movement Montoneros along with Fernando Abal Medina, who developed a romantic relationship with her.  She played a key role in the kidnapping and killing of General Pedro Eugenio Aramburu. The Revolutionary Movement 8th October (MR8) (in Portuguese: "Movimento Revolucionário 8 de Outubro") was formerly a Brazilian urban guerrilla group. The Movimiento Nacionalista Tacuara (MNT, Tacuara Nationalist Movement) was an Argentine far right movement in the 1960s, which later integrated Juan Perón's right-wing “Special Formations”.  Linked to the more conservative sectors of the Peronist movement, and directly inspired by Julio Meinvielle's Catholic pronouncements, Tacuara defended nationalist, Catholic, anti-communist, antisemitic and anti-democratic ideas, and had as its first model the Spaniard Primo de Rivera's fascist Falange.  Its main leaders were Alberto Ezcurra Medrano, Joe Baxter, Oscar Denovi and Eduardo Rosa.  Various contradictory movements emerged from this group.  After three important splits in the early 1960s, the police cracked down on most factions on March 1964.  A year later, the entire MNT was outlawed by President Arturo Illia (UCR).  Composed of young people from right-wing backgrounds, it has been called the "first urban guerrilla group in Argentina". David Graiver (1941 — 1976) was an Argentine businessman and banker who was investigated in the 1970s for alleged money laundering of US$17 million for the Montoneros, a leftist guerrilla group.  He was indicted for embezzlement after his reported death by Manhattan District Attorney Robert Morgenthau, who had thought he might have faked his death, because of the September 15, 1976 failure of American Bank & Trust.  This was the fourth-largest bank failure in United States history at the time, and Graiver's banks in Argentina and elsewhere also failed.  A New York court declared Graiver officially dead on January 15, 1979, clearing the way for resolution of some outstanding financial issues. The Peronist Armed Forces (in Spanish: "Fuerzas Armadas Peronistas" - FAP) was an Argentine Left-wing Peronist urban guerrilla group created in 1968 active during the 1960s and 1970s.  The organization apply terrorism and strike directly against the Argentina state forces.  Led by Envar "Cacho" El Kadri.  His appearance came on 17 September 1968 with an unsuccessful armed action in Taco Ralo, Tucumán. The Liga Comunista 23 de Septiembre (English: September 23rd Communist League ), or LC23S, was a Marxist-Leninist urban guerrilla movement that emerged in Mexico in the early 1970s.  The result of the fusing of various armed revolutionary organizations active in Mexico prior to 1974 in hopes of creating a united front to combat the Mexican government; the name was chosen to commemorate an unsuccessful guerrilla assault on the barracks in Ciudad Madera in the northern state of Chihuahua led by former schoolteacher Arturo Gámiz and the People's Guerrilla Group on September 23, 1965.  The LC23S' militancy was made up mainly of young university students who saw any hope of a peaceful political transformation die in the aftermath of the 1968 student movement and them be buried in 1971.  Its long term objective was the “elimination of the capitalist system and bourgeois democracy, which would be replaced by a socialist republic and the dictatorship of the proletariat”. Juan Manuel Abal Medina (born March 1, 1945) is an Argentine journalist and politician who served as Secretary General of the Peronist Movement between 1972 and 1974, and would later become a prominent lawyer in Mexico. The National Liberation Army (Spanish: Ejército de Liberación Nacional, ELN) is an armed group involved in the continuing Colombian armed conflict, which has existed in Colombia since 1964.  The ELN advocate a composite communist ideology of Marxism and liberation theology.  They conduct military operations throughout the national territory of Colombia; in 2013, it was estimated that the ELN forces consisted of between 1,380 and 3,000 guerrillas.  The ELN is the lesser known of two communist guerrilla armies who operate in Colombia; the other guerrilla army is the Revolutionary Armed Forces of Colombia (FARC–EP) who are Marxist–Leninist in their approach to the national liberation of Colombia.  According to former ELN national directorate member Felipe Torres, one fifth of ELN supporters have taken up arms.  The ELN has been classified as a terrorist organization by the governments of Colombia, Peru, United States, Canada and the European Union. Montoneros (Spanish: "Movimiento Peronista Montonero-MPM" ) was an Argentine leftist terrorist and urban guerrilla group, active during the 1960s and 1970s.  The name is an allusion to the 19th century cavalry militias, called Montoneras, who fought for the Partido Federal during the Argentine Civil Wars.
Answer: Montoneros