It's a murky story little known even to Brazilians, a small-scale rebellion violently crushed deep in the Amazon jungle.
For years, military chiefs pretended it had never happened. But pressure is mounting on authorities to open files, summon witnesses and finally disclose the fate of guerrillas who fought against a military dictatorship in the early 1970s.
Families of the dozens of people missing from the rebellion are raising old questions: How many died in battles with the army? Were some summarily executed? Most important, where are the bodies?
Little is known of the events beyond that communist militants recruited peasants for the uprising along the Araguaia River, in a sparsely populated region in northwestern Brazil. The military's silence and the exuberant jungle growth have made it nearly impossible to find evidence of the fight.
A few weeks ago, only a few empty cartridges and scattered boxes of medicine were found in the first official search for remains of any of the rebels who tried to overthrow the military government in 1972-73.
"There were indications of a military action in that place. But no bones were found," said Nilmario Miranda, the government's human rights secretary.
Suzana Lisboa, a rebel's widow who took part in the search, contended that it would be different if the military would disclose possible grave sites and discuss the events of the 1970s.
"Without that help, this search was like looking for a needle in a haystack," she said in an interview. "Besides, people in the region are still afraid of the army. They don't help either."
The seven-day search was led by two former soldiers who had told a weekly magazine that they believed they knew the place where five guerrillas were buried three decades ago.
More than 60 guerrillas fought in the rebellion, and most did not return.
The little available information suggests the army knew of the uprising in advance and attacked first. For more than a year, soldiers and three bands of guerrillas fought in skirmishes and ambushes. Yet there are no official records of rebels' deaths -- or even of the rebellion itself.
Demands by relatives for the rebels' remains were ignored for years.
They got new hope with last year's inauguration of President Luiz Inacio Lula da Silva, a democratically elected former union leader whose allies include some who supported or fought with the guerrillas. But earlier this year, a government lawyer objected when a judge ordered the military to open files and summon witnesses, and the case is now before an appeals judge.
Uncovering the history of the revolt is difficult, because democracy came about gradually in Brazil, and without the demands for retribution and an accounting that marked the end of military rule in other South American countries such as Argentina and Chile.
"There were no vendettas, no trials here," said Luciano Dias, an analyst at the Institute of Political Studies in Brasilia, the capital.
"But I must also say that there were not so many deaths either. Officially, those who died under the dictatorship were close to 200. Not so many if you compare this with the figures of neighboring countries, where missing and killed ones were in the thousands."
The instigators of the Araguaia rebellion hoped their peasant war would create a "liberated zone" in northern Brazil that could be the base for the eventual conquest of the rich south.
The rebels had to deal with savage wilderness, lack of food and scarce water, as well as fighting the army. By the end of 1973, more than a year after fighting broke out, the uprising was defeated.
"There were no more guerrillas, and the armed forces was not interested in having prisoners," said Crimeia Almeida, a survivor who said she left the campaign in August 1972 because she was pregnant. "The army was simply hunting those who were still alive. Most were executed and their bodies beheaded while others had their hands cut off."
She said she was taken into custody by the military that December and forced to view pictures of the headless bodies of some of her comrades. "It was part of torture sessions; it was grotesque."
The government did not formally admit that the rebellion had occurred until the early 1990s, when it decided to make compensation payments to relatives of some dead rebels.
No government records of the revolt ever turned up, and recently Defense Minister Jose Viegas shocked human rights groups by declaring that all guerrilla-related documents had been burned in the late 1970s.
Elizabeth Silveira da Silva, who lost a brother in the rebellion and heads the Brazilian human rights group Torture Never Again, said civilian governments have helped keep the rebellion's events secret because they fear military leaders.
"There was no combat at all in the final days of the campaign, when the guerrillas were being hunted down," she said. "It was simply an extermination. They don't want to show that."