An old man, thin and stooped, raised a wooden stick over his head and swung it down with both hands. This, he said, was how he executed fellow villagers 37 years ago, striking their necks with an iron bar. The kneeling victims, tied together by their thumbs, tumbled two by two into a hole, now a mass grave.

"I was ordered to kill these people by the army," said Katirin, 75. "If I refused, they would shoot me. . . . I was so afraid, I just did it."

As Katirin demonstrated how he executed people in the 1960s, a widow, Supiyem, watched silently, her eyes cold. Her husband was among those slain on this remote hill at the eastern end of the Indonesian island of Java.

Supiyem, a petite woman of 60, had trudged a mile through the forest with Katirin and four other victims of the violence, crossing a brook and passing a verdant rice paddy, until they reached this place, known as Luweng Tikus, or the Rat Hole. The relatives of the victims expressed a burning desire to reveal the truth. For Katirin, the killer, it apparently was a gesture of atonement.

From 1965 to 1971, perhaps half a million people were killed during the dictatorship of Gen. Suharto, who governed the country for three decades. Hundreds of thousands more were imprisoned in a purge of supposed communists and leftists. Many victims were peasants like Supiyem's husband, Duryadi, who knew little of Marx or Mao.

No independent investigation has ever been conducted; no one has been held to account. Indonesian officials have been loath to face the past. The survivors, emboldened by the end of the Suharto dictatorship in 1998, have only recently begun breaking their silence to set history straight. They want the world to know about the mass killings and to get Indonesia to face its past.

Katirin is one of the few living witnesses to the 1968 massacre of at least 100 villagers over several weeks at the Rat Hole, in the woods of Lorejo village. The unmarked mass grave is among hundreds of stony, muddy and watery tombs.

Today, survivors are taking action on various fronts. One group this year filed a class action suit against the government, seeking $40 trillion in reparations -- a symbolic sum -- and an apology for policies that banned them and their children from state jobs or running for office. A youth wing of the country's largest Muslim civic group, which participated in the killings, is trying to reconcile with victims' families. A few researchers are trying to identify mass grave sites. Historians are recording survivors' stories in a bid to preserve memories before this generation dies.

The task is monumental. Militant groups threaten violence against those who want to bring this past to light. Local military and government officials have tried to thwart researchers' efforts. Sometimes the survivors' own families ridicule them. In one case, a former political prisoner's family has him under virtual house arrest in Jakarta to prevent him from publicizing his story.

Tension on a recent Saturday at the Rat Hole was evident between Katirin and Supiyem, who live in neighboring villages. They were here at the invitation of Putmuinah, 76, a tough-minded former political prisoner who is encouraging survivors to speak out.

"What happened?" Supiyem said, sitting on the wheat-colored grass under an acacia tree, demanding to know more.

"The situation wasn't clear," replied Katirin, sitting a few yards away, his words tumbling out in agitation. "This was not what I wanted." His voice trailed off.

Katirin estimated that he killed 10 people (he had previously told a researcher he killed dozens), but none was Supiyem's husband, whose murder left Supiyem a widow with an infant son, Pujianto or "Puput.''

"Did you see Puput's father?" Supiyem asked again.

"It was almost impossible to know since everything was in chaos," he said, avoiding Supiyem's gaze.

Supiyem said that Katirin's role in the killings disgusted her but that she did not hold him accountable. She blames the Indonesian army and the Suharto regime, who bade villagers like Katirin to do their dirty work.

Throughout the early 1960s, bad feelings built between the Communist Party, which supported land reform in rural areas, and small landlords. In October 1965, following the murder of six top generals under murky circumstances, Suharto took control of the Indonesian army. The army then waged a ruthless campaign to wipe out the Communist Party and its supporters, who were blamed for the murders. Though the party members were nominally Muslim in this predominantly Muslim country, their opponents demonized them as bloodthirsty atheists bent on seizing land and power.

Suharto and his successors have never acknowledged the army's involvement in the massacres.

The killings here in south Blitar, were part of state-sanctioned brutality against people in thousands of villages across Indonesia, said Albertus Suryo Wicaksono, a researcher who in 2002 spent one week excavating Luweng Tikus. The 1968 massacre here was part of a four-month army campaign ordered by Suharto to finish off the party. No one knows the overall death toll from the purges -- guesses range from 300,000 to more than 1 million, but the most credible estimate, several academics said, is 500,000.

For a long time, schoolchildren were shown a documentary each year that blamed the generals' murders on the Communist Party, though who really was at fault is still debated by historians. State media reported that Communist women danced as the generals were castrated and their eyes gouged out. Despite autopsies showing no torture or mutilation, the myth has never been corrected in text books or films and still has currency.

Supiyem had been married only one year when, in August 1968, her husband was killed. Duryadi, a rice farmer, belonged to a farmers group that supported the Communist land reform program. Two of Supiyem's younger brothers were arrested and marched away, never to return. A third brother was detained and released, by his count, 11 times that year.

To save that brother from death, she recalled, she forced herself to serve as "a wife" for the new village head. For seven years, she said, she endured Sarmin, who moved in with her at her parents' house. She cooked and cleaned for him. She slept with him. "I shut down my feelings," she said, staring into the distance. "It was unthinkable."

Sarmin left the village in 1975, when his term ended, she said. He died in the late 1990s.

For years Supiyem dared not speak about what happened, fearing retaliation from authorities. In 2001, an Indonesian human rights group began an investigation. It was her son, Puput, who urged her to talk.

"I said, 'Speak up, Mom,' " he recalled. " 'This is something you should do. If we can bring the truth to light, let's do it!' "

Though nearly 40 years have passed, Supiyem has kept her pledge never to remarry. Her only surviving brother, whose life she saved by sleeping with Sarmin, has recurrent nightmares of drowning in a river. Even Katirin, who was forced to kill, says he is still haunted by the look of "surrender" on his victims' faces.

In 2002, when Wicaksono was excavating the Rat Hole, a natural underground cave some 45 yards deep, a local military officer's son warned him to stop. His team kept going. They hit the first set of bones at 21 yards and found three skulls, enough to prove the mass grave existed. Wicaksono removed a jawbone and a tooth for forensic testing. A farmer, Damin, keeps the bones in a plastic bag in his closet. The bones, Damin said, often make a "clacking" noise at night.

The Rat Hole was the first of 27 mass graves Wicaksono has identified on Java. He has vowed to expand his search, despite efforts to intimidate him.

Near the site, the military erected a monument to the execution of the Communists. Supiyem and other relatives want the mass grave turned into a memorial honoring their dead.

Supiyem knelt next to the Rat Hole. She tossed in handfuls of bougainvillea blossoms and reflected quietly as the magenta and lavender petals fluttered down. She said she took solace in how her husband died: As he was about to fall in, the story repeated in the village goes, he grabbed hold of a soldier and dragged him down with him. Her husband, she said, had died a hero.

Special correspondent Yayu Yuniar and staff researcher Robert Thomason in Washington contributed to this article.

Supiyem, 60, mourns her husband at a mass grave in eastern Java. He was killed during a purge that swept Indonesia in the 1960s.