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Argentina's last dictator and 14 other former military officials were sentenced Friday to prison for human rights crimes committed during the Operation Condor conspiracy. Here is a look at the clandestine program's main features:

WHAT WAS OPERATION CONDOR?

It was a coordinated effort by the military dictatorships in Argentina, Chile, Paraguay, Bolivia, Uruguay and Brazil to hunt down and eliminate opponents and leftists across the continent and beyond. It operated from the mid-1970s to the early 1980s.

HOW DID IT WORK?

Operation Condor officially began in 1975, when South America's dictatorships agreed to start exchanging information on political dissidents, trade unionists, students and anyone suspected of being leftist, especially those who had sought refuge in other countries. According to declassified documents, various U.S. government agencies were aware of the plan.

The covert operation involved the deployment of special transnational teams to kidnap subversive "targets," who were then interrogated and tortured in seven clandestine prisons located on military or police bases in Argentina, Paraguay, Uruguay and Chile. The dissidents were sometimes returned to their country of origin and disappeared.

Condor's agents also assassinated political leaders seen as influencing public opinion against the military regimes. Some of their targets were in the United States and Europe. The September 1976 assassination of Orlando Letelier, the ex-foreign minister of Chile's socialist President Salvador Allende, was the best-known case. Letelier, and his U.S. aide Ronni Moffitt, were killed by a bomb placed in his car in Washington D.C. Investigators found that the Chilean dictatorship's spy agency, known as DINA, and an anti-Castro group, many of whose members had been trained by the CIA, were behind the assassination.

WHO WERE CONDOR'S MASTERMINDS?

Chilean dictator Augusto Pinochet, Paraguay's Alfredo Stroessner, Bolivia's Hugo Banzer, Argentine dictator Jorge Videla and Juan Maria Bordaberry of Uruguay. While no representative of Brazil signed the operation's charter, its government cooperated with the program and dissidents were killed and kidnapped in its territory.

HOW MANY VICTIMS?

According to a 2015 report by UNESCO's International Center for the Promotion of Human Rights, Operation Condor had 376 victims: 177 Uruguayans, 72 Argentines, 64 Chileans, 25 Paraguayans, 15 Peruvians, 12 Bolivians, five Brazilians, three Cubans, two Americans and a Spaniard.