Ben Roberts-Smith knows how it feels to go to war.
But a trip to Vietnam with a group of veterans showed him a side of war he had never experienced.
"It was amazing to see these guys who were shooting at each other 40 years ago and are now able to sit down and have a beer together," he said.
"I can't imagine being able to do that."
Cpl Roberts-Smith, who was awarded the Victoria Cross for bravery in Afghanistan, spent four days revisiting battlegrounds of the Vietnam War and helping reunite the families of fallen Viet Cong with items taken from soldiers' bodies at the time.
Of all the items that were returned, some of which have spent decades tucked away in small military museums, one stuck in Cpl Roberts-Smith's mind.
"It was a picture a Vietnamese soldier had drawn of his wife and on the back of the picture he had written the names of his children," he said.
"When we went back his wife was still alive.
"To be able to give that back to her and see what it meant to her . . . she was overcome with emotion. You can only imagine what that's like.
"It was extremely emotional for them (the Australian veterans) at the point of handing back items to the families." "
The trip, dubbed Operation Wandering Souls, was the work of military researchers at the University of NSW, including Vietnam War veterans.
As well as collecting personal effects to return to the families of lost Viet Cong soldiers, the team has compiled a database of burial sites to help find those Vietnamese still deemed missing in action.
The project was deemed particularly important in part because Vietnamese culture considers those who die in unrecorded graves to be "wandering souls". The personal belongings of someone who has died also have significance.
Vietnam has previously helped Australia find and repatriate its dead soldiers.
Cpl Roberts-Smith said he jumped at the chance to visit.
"To be able to go and see the battlefields was fantastic," he said. "To be able to go with those Vietnamese veterans was a once in a lifetime experience.
"It was a humbling experience to see what it meant to them. I know that feeling, I know why they did what they did.
"From an Aussie point-of-view or a soldier point-of-view I think it was important to go back and pay my respects to the men who lost their lives there."