The last time that Americans were in this part of Laos they were fighting an undeclared secret war, unknown to the American public at the time and barely remembered today. The older women recall hiding from the B52s that rained bombs.

This time there isn’t an M16 or a uniform in sight. What is unfolding in the jungle is part duty, part catharsis. It is a slow, painstaking pursuit against the longest of odds. It is integral to understanding the US and its military.

The young Americans have come because of unfinished business from their nation’s most harrowing military engagement. Their mission is to find the bodies of 1,800 servicemen still unaccounted for in the Vietnam War.

Many of those digging and sifting have come after serving in Iraq, anxious to do the right thing by their forebears while also hoping that the generation of soldiers that follows will not forget them.

Denny Danielson first arrived in South-East Asia as a scared 20-year-old “grunt” from Iowa on a search-and-destroy mission. He is now a forensic anthropologist on his 54th mission, dedicated to finding the remains of his brothers-in-arms who didn’t make it home.

He sees comparisons in the war that he fought and the conflict in Iraq, though not necessarily those of their detractors. “Iraq is like Vietnam in some ways. We are trying to help people who don’t always want to be helped,” he said.

Those they are searching for, the missing in action, or MIA, were soldiers or special forces teams killed in remote jungles, or the dead left during retreats from the battlefield. In Laos many of the MIA were aviators shot down over the Ho Chi Minh trail.

But they are more than names, ranks and serial numbers. Those who never returned hold a powerful grip on the national psyche. America promises the soldiers that it puts in harm’s way that it will always bring them home — alive or dead. It is a question of national honour, the commitment of a nation that prizes the life of each of its warriors and promises them a resting place in the beautifully tended gounds of Arlington National Cemetery. And it is this that makes the men and women of the Joint POW/MIA Accounting Command (JPAC) determined to search for the remains of every last one of them and, if possible, bring them home for a military funeral and burial on American soil.

Mr Danielson’s Marine Corps unit spent a year fighting and dying in Vietnam in 1966. After his military service he became an archaeologist specialising in Native American sites.

As the Marines dig and the hill folk shift buckets Mr Danielson strides restlessly across a jungle clearing stripped bare of vegetation and carefully marked into squares, deciding where to excavate next. Buried somewhere on a hillside hundreds of square metres in area he hopes to find the remains of the pilot and navigator of a Phantom jet shot down by North Vietnamese cannon during a reconnaissance mission in 1969.

The aircraft’s fuselage was long ago sold for scrap metal and after a high-impact crash and explosion, followed by decades lying in acidic soil, there will not be much more to find than rusty lumps of metal, charred bone fragments and teeth, although if the team is lucky they may unearth a wedding ring or a watch. Bereaved families often receive no more remains than enough to fill a matchbox.

Tonnes of soil must be laboriously excavated to find enough human remains for a positive DNA test at the JPAC forensic anthropology laboratory in Hawaii, the biggest of its kind in the world. Burnt bone fragments rarely provide enough material, so finding a molar or a piece of skull in the sieve is a cause for whoops of celebration from the diggers.

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