Media playback is unsupported on your device Media caption After 50 years, the Indonesian government is going to investigate one of the worst massacres of the 20th Century.

Indonesia has decided to investigate one of the darkest chapters of its own history. In 1965 at least 500,000 people died in organised killings of suspected communist sympathisers. But, as BBC Indonesian's Rebecca Henschke reports, the new investigation into that bloody time is re-opening old wounds.

A mass grave in the middle of a forest

There is a spot in the middle of a teak forest, the ground covered with leaves, on the outskirts of Pati in Central Java. Radim, a thin farmer in his 70s, describes what happened here one night in 1965.

Image caption Local intelligence officials were clearly nervous of media at the site of the purported mass grave

"They came on carts pulled by cows...their hands were tied together with rope. They were forced to kneel, then shot in the back by soldiers and kicked into mass graves."

The violence was unleashed after communists were accused of killing six generals in an attempted coup. It was the peak of the Cold War and a power battle between communists, the military and Islamic groups was in full swing.

The army and local militia went on an anti-Communist rampage, killing, it is estimated, at least half-a-million and up to three million people within a year.

Media playback is unsupported on your device Media caption BBC reporter is questioned by officials during visit to alleged grave site

Image caption Radim says he was too frightened to speak out until now

For almost 50 years speaking about that time has been taboo and official history books gloss over the killings.

Where previous governments refused to apologise or even accept that it happened, President Joko Widodo's investigation has seen senior ministers meet with survivors. There is even talk of digging up mass graves such as this.

"I am not afraid anymore, I am proud to tell you the truth. I never thought there would be a time like this. Before I only knew fear," Radim says.

But this clearly doesn't come without risks.

How the investigation makes many nervous

As Radim reveals the location of the grave, 15 men in plain clothes - local intelligence officials - surround us and the atmosphere is tense. The investigation has angered and unsettled many in the military elite and Muslim organisations accused of taking part in the killings.

Image caption Local intelligence officials appeared as the BBC visited the site of an alleged mass grave

In central Java where most of the killings took place anti-communist banners have been erected. Vigilante groups have shut down discussions about Marxism at universities. Soldiers even briefly detained some students for wearing red T-shirts with a picture of a hammer and sickle inside a coffee cup.

It's also creating divisions in the government.

Defence Minister Ryamizard Ryacudu has met with Islamic vigilante groups and resists these moves to dig up the past.

"I am responsible for security in this country. I need to make sure there are no more conflicts. ...if we keep looking back we are not going to go forward," he told the BBC.

He is worried that those responsible for the massacre could be indicted for crimes against humanity.

Those with a stake in keeping the status quo fear the consequences of reviving the divisions of that time. But even if it does re-open old divisions, many welcome the chance to embrace the truth.

Those happy to admit they killed

It is easy to find someone who will proudly tell you how many they killed in 1965 and how they did it.

Image caption Burhanaddin is among those who killed at the time

Burhanaddin ZR says he killed more people than he could count and shows no remorse.

"There is no need for reconciliation."

"The only path is they need to let go of their angry feelings," he says of those that lost relatives. "They just want revenge because their family members were victims in our raids."

In the Oscar-nominated documentary The Act of Killing a group of men acted out the murders in horrific detail. In many areas killers live close to the families of the dead. Land and property that was illegally confiscated has never been returned.

Until recently they have always thought of themselves as heroes because they were supported by the government and mainstream media. Many of the executions were directly committed by the security forces. The largest Muslim organisations are also accused of taking part.

President Widodo's move has made them all nervous.

The stigmatised still feel pain

Thousands were tortured and imprisoned for years without trial. When they were released their identity cards marked them as former political prisoners. It was not until 2004 that the label was officially removed from the ID's.

For decades they and their families were banned from holding government jobs, entering the military or the police. Their children were stopped from going to school and university. Families were torn apart as children stayed away from their parents in an attempt to live without stigma.

Only in 2005 did this change.

Image caption The events of 1965 have remained taboo in Indonesia for almost 50 years

The survivors afraid to speak out

In the 1960s the Indonesian Communist Party was the second largest in the world. Its members were mostly intellectuals, farmers, artists and social activists. To escape the purge some went into exile in the Netherlands and Russia.

For decades they weren't allowed to come home, even to bury their loved ones. Even now when high-profile exiles return they are monitored by intelligence agents.

The youth who don't know their own history

Under General Suharto, who effectively took power shortly after the attempted coup and remained until 1998, school children were forced to watch a graphically violent three-hour-long government film about the brutal alleged coup by the communists.

Image caption Accused of being communists or communist sympathisers, hundreds of thousands, possibly millions were murdered

Children were indoctrinated to believe that communists were evil. The favourite uncle of Eric Sasona, a film critic and political scientist, was one of the killers. He used to boast about murdering suspected communists with a hatchet. It wasn't until recently that he heard a different story.

"When I watched the documentary The Act of Killing - where the killers performed what they did so proudly - I thought of my uncle. I felt sick in the stomach and I had to turn it off after a few minutes," Mr Sasona said.

He believes his uncle was simply a product of the time, but he does think Indonesia needs to talk about what happened.

"We have to end the culture of impunity that still exists; we have to end this because people can get away with their crimes. Coming to terms with our past is the key to solving today's problems like corruption."

Given the deep divisions, hopes of justice or national reconciliation are slim. But the government has made the decision to open up a Pandora's Box, something many thought would never happen in their lifetime. But where it will lead is not clear.