The Montonero Peronist Movement (Movimiento Peronista Montonero) was an Argentine left-wing Peronist guerrilla group, active during the 1960s and 1970s. Its motto was venceremos ("we will win"). After Juan Perón's return from 20 years of exile and the June 20, 1973 Ezeiza massacre, which marked the definitive split between left and right-wing Peronism, the Montoneros were expelled from the Justicialist party in May 1974 by Perón. The group was almost completely dismantled in 1977, during Videla's dictatorship.
Montoneros initiated a campaign to destabilize by force what they deemed was a pro-American regime. Claiming retaliation against the June 1956 León Suárez massacre and Juan José Valle's execution, Montoneros kidnapped and executed former dictator Pedro Eugenio Aramburu (1955–1958) and other citizens who they said collaborated with him, such as unionists, politicians, diplomats, and businessmen. They financed their operations by kidnapping and collecting ransom for businessmen or executives, making as much as $14.2 million in a single abduction for an Exxon executive in 1974.
On March 11, 1973, Argentina held general elections for the first time in ten years. Perón loyalist Héctor Cámpora became president, before resigning in July to allow Perón to win the new elections held in October. However, a feud developed between right-wing Peronists and Montoneros. The right-wing of the Peronist party, the unions, and the Radical Party led by Ricardo Balbín, favoured a social pact between trade unions and employers rather than a violent socialist revolution. Right-wingers and Montoneros clashed at Perón's homecoming ceremony during the June 20, 1973 Ezeiza massacre, leaving 13 dead and more than 300 wounded. Perón supported the unions, the radicals led by Ricardo Balbín and the right-wing peronists, among whom José López Rega, founder of the Alianza Anticomunista Argentina ("Triple A") death squad, which had organized the massacre, along with the Peronist right-wing.
In May 1974, Montoneros were expelled from the Justicialist movement by Perón. However, Montoneros waited until after the death of Perón in July 1974 to react, with the exception of the assassination of José Ignacio Rucci, general secretary of the CGT (General Confederation of Labour) on September 25, 1973, and some other military actions.
Montoneros claimed to have what they called the "social revolutionary vision of authentic Peronism" and started guerrilla operations against the government. In the government the more radically right-wing factions quickly took control; Isabel Perón, President since Juan Perón's death, was essentially a figurehead under the influence of former federal police corporal José López Rega.
On July 15, 1974, Montoneros assassinated Arturo Mor Roig, a former foreign minister. In September, in order to finance their operations, they kidnapped two members of the Bunge and Born business family. They demanded and received as ransom $60 million in cash and $1.2 million worth of food and clothing to be given to the poor. This ransom is the highest ever paid according to the Guinness Book of Records.
The Triple A under López Rega's auspices began hunting down, kidnapping, and killing Montoneros and members of Ejército Revolucionario del Pueblo (ERP) as well as other leftist militant groups, or anyone in general considered a leftist subversive, be it deputies or lawyers.
Montoneros and ERP went on to attack business and political figures throughout Argentina as well as raid military bases for weapons and explosives. The Montoneros killed executives from General Motors, Ford and Chrysler. The group also sank an Argentine destroyer, the ARA Santisima Trinidad in 1975. On July 2, 1976 they detonated a powerful bomb in the Argentine Federal Police in Buenos Aires, killing 24 and injuring 66 people. Their numbers (at their strongest, just a few thousand) were no match against the highly organized and ruthless branches of the military, who under the cloak of paramilitary forces (operating out of uniform and without any accountability) didn't hesitate to kidnap and kill even remote acquaintances of militants, or force captured members, through torture, to become informers and turn in their comrades-in-arms.
By the time Videla's military Junta took power in March of '76, approximately ten thousand political prisoners were being held in various prisons around Argentina, some with political connections and some just guilty by association. These political prisoners were held throughout the years of the dictatorship, many of them never receiving trials, in prisons such as La Plata, Devoto, Rawson, and Caseros.
On 24 March 1976 Isabel Perón was ousted and a military junta installed, led by General Jorge Rafael Videla. The Junta reinforced counter-revolutionary operations, leading to the so-called "Dirty War", which saw approximately 30,000 victims. The Junta relied on mass arrests, torture, and executions without trial to stifle any political opposition. The victims' bodies that were not helicoptered out into the Atlantic Ocean were left on the streets as an example to militants still at large. The Montoneros suffered heavy losses in 1976 - 1980 out of around 7000 active supporters were killed, with the rest forced to scatter.
Montoneros were effectively finished by 1977, although some did fight on until 1981. During the Falklands War against Great Britain, the Argentine military conceived the failed Operation Algeciras, a covert plan to support and convince some Montoneros (appealing to their patriotism) to sabotage British military facilities in Gibraltar. Argentina's defeat led to the fall of the Junta, and Raul Alfonsin became president in December 1983, thus initiating the democratic transition.