In 1980, a young, left-wing Argentine militant named Horacio Campiglia was abducted in Rio de Janeiro and then taken to a military base in Buenos Aires, never to be heard from again.

In the southern cone, Mr. Campiglia's story is a familiar one – he is one of tens of thousands of dissidents who were "disappeared" – abducted and murdered – by military dictatorships in the region in the 1970s and 1980s.

Now, the former government officials responsible for those disappearances are being put on the stand for the first time.

A Buenos Aires courthouse heard charges today against 25 defendants accused of human rights abuses during Operation Condor, a secret, decade-long campaign by six allied military governments to do away with left-wing subversion. Crucially, they conspired in order to track down activists who were in exile in neighboring countries.

"The trial is historic as it's the first to deal with the repression coordinated between Latin American dictatorships," says Carolina Varsky, the lawyer representing Campiglia's relatives.

The regimes of Augusto Pinochet, military leader of Chile from 1974 to 1990, and Alfredo Stroessner, Paraguay's former strongman president, colluded with leaders in Uruguay and Argentina, documents known as the "Archive of Terror" show. Bolivia and Brazil later joined the operation as well.

The trial is expected to last two years and will call on around 500 witnesses. Judges will rule on the cases of 106 victims of Operation Condor and 65 more in a related operation. The majority are Uruguayans disappeared in Argentina, but there are also Paraguayan, Chilean, Bolivian, Argentine, and Peruvian victims.

The defendants include Jorge Videla and Reynaldo Bignone, former de facto presidents during Argentina’s 1976-83 military rule, who are already serving life sentences for their role in the dictatorship’s "Dirty War."

They sat motionless in court as they were accused of "illicit association" and "deprivation of personal liberty." They cannot be accused of homicide since the victims' bodies were never found.

The only non-Argentine among the defendants was Uruguayan Manuel Cordero, a former colonel charged with human rights violations at the Orletti torture center in Buenos Aires.

“This is a huge step to achieve the truth internationally,” says Atilio Borón, an Argentine political scientist who studies social movements and democracy. Human rights have become a cornerstone of Argentine politics since Néstor Kirchner, the predecessor and late husband of current President Cristina Kirchner, overturned impunity laws.

“Argentina has been able to push for justice because civil society is today stronger than the military, but other countries have not managed to swing the balance,” Mr. Borón says, referencing the difficulties President Dilma Rousseff has experienced in putting leaders from Brazil’s 1964-85 military rule in the dock. Mr. Pinochet also died in impunity, and Uruguay’s supreme court ruled last week that a law overturning amnesty on dictatorship crimes was unconstitutional.

Operation Condor was also backed by the United States, as American author John Dinges revealed in his 2004 book, "The Condor Years." Indeed, last year, an Argentine federal judge requested that former Secretary of State Henry Kissinger be interrogated as part of the investigation but, according to local media reports, he did not receive a reply.

Get the Monitor Stories you care about delivered to your inbox. By signing up, you agree to our Privacy Policy

The investigation into Operation Condor began in the late 1990s, when the impunity laws were still effective.

"We're delighted that after years of struggle this has finally come to trial," says Alcira Ríos, the lawyer of a Paraguayan victim.