By John Sudworth
BBC News, Daegu, South Korea
Experts have been sifting through earth to find human bones
For decades, Lee Tae-joon has wondered what became of his cousin, his childhood companion, who disappeared without trace at the start of the Korean War.
Now he thinks he knows the answer.
At an abandoned cobalt mine near the South Korean city of Daegu, evidence of a massacre is being slowly uncovered.
With brushes and trowels, working ankle-deep in water, a team of archaeologists is sweeping away the top-soil to reveal a mass of human bones.
It is thought that this cold tomb contains the bodies of up to 3,000 people who were executed and then thrown into a vertical mine shaft.
Mr Lee believes his cousin was one of them.
"My heart really breaks when I think that all this killing took place without any judicial process, and by our own forces," he said.
'Hostility and hatred'
At the outbreak of the Korean War, his cousin, like many thousands of suspected Communist sympathisers, was rounded up by the South Korean police.
That large numbers of these political prisoners were shot to stop them joining troops advancing from the north is the grim truth now being pulled from the country's soil.
It has taken this long to unearth because, for much of the post-war period, South Korea's military dictatorships made this kind of investigation impossible.
The families of those who disappeared suffered in silence.
Mr Lee wants to know what happened to his cousin, missing for over 50 years
"It was very difficult," Mr Lee said. "After the war, even the slightest suggestion that your family had leftist sympathies would leave you open to hostility and hatred."
In 2005, South Korea finally established a Truth and Reconciliation Commission. Its 240 staff have interviewed hundreds of witnesses and relatives of the victims.
Last year, they started digging. Just a handful of 160 suspected mass-grave sites have been uncovered so far.
In total, they are estimated to contain the remains of more than 100,000 civilian prisoners and suspected leftists.
And there is strong evidence to suggest that the 1950 summer of slaughter took place in the full view of South Korea's American allies.
Photos of the executions, taken by US soldiers, were stamped "secret" and filed away in Washington for years.
Their eyewitness accounts were passed to the top of the chain of command.
"There is proof that it was reported to the very top," said Kim Dong-choon, of the Truth and Reconciliation Commission. "US soldiers took pictures and reported back to their superiors."
News reports have suggested that the Americans saw it as an "internal matter".
The British, though, did take some action, seizing "Execution Hill", outside Seoul, to prevent further killings.
But 82-year-old Kim Man-sik, one of the few South Koreans left alive who admits to having taken part in the executions, pleads for a fuller understanding of the circumstances of war.
In the midst of a civil conflict, with the front line just a few miles away, he says the military policemen under his command felt they had little choice but to follow orders.
"On two occasions my unit was told to collect suspected leftists from the police, and we conducted group executions," he said.
"But you have to understand the situation at the time, our forces were in a very disadvantaged situation and cornered."
The Truth and Reconciliation Commission has until 2010 to complete its task.
An uncomfortable truth has been airbrushed from the history of the Korean War, which has long attributed almost all atrocities to the communists in the North.
More than half a century on, it is a new generation in the South that are coming to terms with the thought that in war terrible deeds are not only the preserve of the enemy.
But the commission cannot compel witnesses to give evidence, nor can it impose any sanctions on the perpetrators.
There is concern amongst its supporters that its mandate is too short, and its powers too weak, to do justice to its cause.