When the Argentine military began seizing power on March 24, 1976, it was the beginning of the darkest hour in the country's history -- and marked another chapter in the brutal wave of repression and torture across South America.
As in Uruguay and Chile, the military hunted down everyone who appeared to be on the political left. Terrorists disappeared along with idealists -- lost forever to torture chambers and eventual death.
Human rights activists estimate as many as 30,000 people were killed.
"Thirty years later, Argentina has achieved amazing progress in coming to terms with the aftermath of the dictatorship, and in Uruguay and Chile there also is a new dynamic to watch," said political scientist Ruth Fuchs of the Institute for Ibero-American Studies in Hamburg.
In Argentina, amnesty for the military has been lifted and suspects must stand trial. Facilities where people were tortured have been converted to memorials and victims have been compensated.
In Uruguay, under the new President Tabare Vazquez, the bodies of people labeled "disappeared" have been exhumed, and Chile has elected a new socialist president, Michelle Bachelet, who personally suffered torture and horror under dictator Augusto Pinochet's reign.
After years of legal wrangling, the tables have turned and Pinochet faces court trials for his involvement in ordering killings and torture of his opponents.
"We are the children of the Mothers of Plaza de Mayo," said Argentine President Nestor Kirchner, referring to the fundamental changes.
Kirchner was 27 years old when the mothers of the disappeared risked their lives with their first demonstration on Plaza de Mayo in 1977, the famous public square in Buenos Aires, to demand information about their loved ones.
"Currently in power is a generation that was dissatisfied with the previous politics," Argentine sociologist Horacio Verbitsky said.
The presidents who followed the end of the dictatorship in Argentina in 1983, Raul Alfonsin and Carlos Menem, both now in their late 70s, belonged to a generation that had suffered under military rulers, but was also willing to make an arrangement with them to see them step down.
Fuchs said that while there were differences among the three countries, they all had in common the long period of time that has been needed "to completely work through the past."
Human rights organizations had to get up and running to make the long strides over the past three decades in setting standards for human rights at the international level, said Fuchs, who has studied the subject for years.
Just after the end of the dictatorships, there was an initial push to uncover the brutality and injustice, and there were attempts to punish the offenders. Then there were years of silence until a new cycle of remembrance was placed on the political agenda, Fuchs said.
The most recent progress is closely linked to the generational change of the politicians in power. At the same time the results of human rights groups' reappraisal of the crimes of the past have come to the fore.
Verbitsky stressed the importance of prosecuting the people who committed the crimes.
"Letting such crimes go unpunished results in all other possible offenses going unpunished and undermines the entire political and judicial system," Verbitsky warned. "One cannot come to an arrangement with such a past because it infects everything."