The ERP leadership chose to send Compañía de Monte Ramón Rosa Jiménez to the province of Tucumán at the edge of the long-impoverished Andean highlands in the northwest corner of Argentina.

Ítalo Luder issued the presidential decree 261/1975 which stated that the "general command of the Army will proceed to all of the necessary military operations to the effect of neutralizing or annihilating the actions of the subversive elements acting in Tucumán Province.

The logistical and operational superiority of the military, headed first by General Acdel Vilas, and from December 1975 by Antonio Domingo Bussi, succeeded in crushing the insurgency after a year and by destroying links the ERP, led by Roberto Santucho, had earlier established with the local population.

Brigadier-General Acdel Vilas deployed over 4,000 soldiers, including two companies of elite army commandos, backed by jets, dogs, helicopters, U.S. satellites and a Navy Beechcraft Queen Air B-80 equipped with infrared surveillance assets.

These "annihilation Action decrees" are the source of the charges against Isabel Perón, which called for her arrest in Madrid more than thirty years later, in January 2007, but she was never extradited to Argentina due to her advanced age.

[19] Second Lieutenant Daniel Arias and Corporal Juan Orellana of the combat team were also wounded and two guerrillass were killed in this action, Héctor Enrique Toledo and Víctor Pablo Lasser.

On 11 May, an Army officer, Second Lieutenant Raúl Ernesto García was killed while is unit manned a checkpoint during a fierce exchange of fire with a car-load of guerrillas travelling along Route 301 in Tucumán.

On 28 May, a four-hour gun-battle took place between 117 guerrillas and the 32-strong 1st Platoon from the 5th Mountain Engineer Company that had been assigned to carrying out repairs as part of a hearts-and-mind campaign in the schools of Manchalá, Yacuchina, Yonopongo and Balderrama in the Tucumán countryside, resulting in several casualties on both sides.

[26] In the face of heavy army reinforcements, the guerrillas ceased contact and escaped to their operating base located in El Tiro via three routes, leaving two of their own dead, Domingo Villalobos Campos, a Chilean nation and Juan Carlos Irurtia.

On 5 September an army platoon operating outside Potrero Negro falls into an ERP ambush and the officer in charge, Second Lieutenant Rodolfo Berdina is mortally wounded and Private Ismael Maldonado is killed at the very start of the firefight.

[32] On 10 October, a UH-1H helicopter piloted by Second Lieutenant Oscar Delfino was hit by small arms fire during an offensive reconnaissance mission near Acheral, killing its door gunner, Corporal José Anselmo Ramírez and wounding Captain Armando Valiente (a commando).

On 24 October, during a clash that took place with ERP guerrillas on the banks of Fronterista River, Second Lieutenant Diego Barceló and Privates Orlando Moya and Carlos Vizcarra from the 5th Brigade were killed.

Romero was able to escape in the immediate confusion but he would be shot dead along with another guerrilla, Isidro Fernández, in a confrontation with security forces in the large industrial sector of Avellaneda in the Argentine capital.

[45][46] On 5 May, during night mission, an army UH-1H crashed on the banks of Río Caspichango, killing five of its seven crew members, Captain José Antonio Ramallo, Lieutenant César Gonzalo Ledesma, Sergeant Walter Hugo Gómez and Corporals Carlos Alberto Parra and Ricardo Martín Zárate.

[47] On 10 May, Private Carlos Alberto Fricker was shot dead by nervous sentries while stationed in Famaillá or died by suicide, although journalist Marcos Taire suggested that the Argentine Army was involved in a dastardly action.

[48] Then Second Lieutenant César Milani would be signalled out as the officer responsible for the murder and disappearance of Private Fricker and a number of other conscript soldiers serving in the 5th Brigade at the time, and as future commander of the Argentine Army would face the full wrath of the Argentine press and forced to resign his post and spend time in jail until it was proven in a court of law that he never actually served in Tucumán province and was consequently absolved of charges of having committed crimes against humanity and released from jail.

[54] The officer (César Milani) falsely accused of orchestrating the murders of Second Lieutenant Pimentel, Sergeant Lai and Private Cajal and others would spend considerable time in jail before being proven innocent in a court of law and set free.

He would be hunted down and killed on 9 August 1976 at Banda del Rio Salí, Cruz Alta, Tucumán province in a joint operation involving the army and police.