In April 1964, a coup d'état overthrew João Goulart's Government, starting the Military Dictatorship in Brazil, Leonel Brizola was the only political leader to support the president, sheltering him in Porto Alegre and hoping a bid to rouse the local army units towards the restoration of the toppled regime could be made.

Promoted by the Revolutionary Nationalist Movement (MNR), an organization initially based in Montevideo, the guerrilla had financial support from Cuba, obtained through negotiations between Leonel Brizola, assisted by the A.P (Popular Action), and the Cuban government.

Its members remained there for a few months, carrying out training and reconnaissance of the region and were arrested by the Minas Gerais Military Police after being reported by the population themselves.

The guerrillas, around twenty exhausted and hungry men - some seriously weakened by the bubonic plague - were arrested at the site where they were sheltering or in neighboring cities.

A large joint operation between the Army and the Air Force was then set up, with support from the police, to eliminate other guerrillas who might be hiding in the mountains.