 On 5 October 1975, the Montoneros carried out a complex operation against a regiment of the 5th Brigade.During this attack named "Operation Primicia" ("Operation Scoop") a Montoneros force numbering an estimated several hundred guerrillas and underground supporters, set in motion an assault on an army barracks in Formosa province.On 5 October 1975, Montoneros members hijacked a civilian airliner bound for Corrientes from Buenos Aires.