Atop a half-mile-high mountain deep in the heart of the A Shau Valley in central Vietnam, a poisonous worm snake winds itself onto the edge of a spade. After a fleeting glance, the U.S. sergeant holding the spade, Tammi Reeder, 34, flicks her wrist and flings the vermilion serpent into the double-canopy jungle surrounding this mountaintop enclave. It is the fourth such snake in an hour and about the millionth over the past several weeks, so this group of 10 U.S. military personnel, 2 civilian anthropologists, and more than 70 Vietnamese workers have developed a resigned tolerance for reptiles.

We are in a cloud forest, three miles from the Laos border in the A Luoi District, an hour’s helicopter ride from anything. Verdant trees—banana, banyan, traveler’s palm, and cassia—are rooted in curried mud. A wet layer of humidity wilts the jungle. The group’s mission is to find and repatriate a warrant officer whose Huey helicopter went down in May of 1967 with three other crew members. Those three were rescued within 48 hours. In the days afterward, several attempts were made to retrieve him too, but heavy enemy fire made it impossible.

This search is one of more than 15 that take place annually under the charge of the Department of Defense’s Joint POW/MIA Accounting Command (JPAC) in Hawaii—400 military personnel and civilian anthropologists and archeologists who so far have conducted more than 80 Prisoners of War/Missing in Action operations in the Philippines, Cambodia, Laos, Vietnam, North Korea, Burma, and many other places. On average, JPAC identifies 2 soldiers a week in its forensic laboratory, which is the largest in the world. There remain today more than 78,000 missing soldiers from World War II (of which 35,000 are deemed recoverable), more than 1,800 from Vietnam, 8,100 from Korea, 126 from the Cold War, and 1 from the 1991 Persian Gulf War.

Clara Barton answered 44,000 inquiries about the missing, and located 22,000 soldiers.

To decide which of this multitude to try to locate, JPAC’s Casualty Data section analyzes each case, assessing such factors as the political stability of the country, available weather windows, safety, and accessibility. Once adequate information has been collected and analyzed, the intelligence, operations, and laboratory sections decide whether or not to pursue a recovery. Basically, they go for the easiest to reach—an approach that gets more difficult with every passing year.

All the cases involve the dead. The wistful, angry conviction that grew up in America after Vietnam that prisoners were still being held has spurred JPAC to pursue thousands of reports of “live sightings” throughout Southeast Asia. Not a single case was found to be credible. While they continue to follow up any such leads, investigators do not believe that any living soldiers are being held from past wars.

Augustus Goodman, the 30-year-old anthropologist in charge of this mission, has the regal stance of a nineteenth-century explorer and the quiet manner of a philosopher. “It’s an amazing endeavor. Not many other cultures go as far as—” He stops. Perching on a small rock, he gazes out to the jungle and away from the work going on behind him, where the sound of shifting, sifting earth is constant and quiet and Peter, Paul & Mary songs from a generation ago filter from a tiny tape player hung on a tree limb. Goodman wears a baroque wedding band of gold and gunmetal on a parachute cord around his neck, and a torn-off corner of a T-shirt tied kerchief-style over his shoulders. He speaks Greek and is learning Vietnamese. “How far we go to honor those who died,” he continues after the pause. “It says a lot about our society.”

The United States has not always gone so far. The search for missing soldiers postwar is relatively new. Historically, U.S. soldiers were given a burial only when time, family connections or money, and manpower would allow, and even then it tended to be unceremonious and expeditious. The missing, however, remained eternal mysteries to their families.

It wasn’t until the Civil War that any attention was afforded the missing at all. Then the Army’s Quartermaster General’s Office published lists of burial rosters from 72 national cemeteries and over 300 local cemeteries to aid families in their search for missing soldiers. Roughly half the 316,000 Union dead who had been buried were eventually identified, but Confederates were far more elusive. Few were buried in marked graves, and typically only officers were afforded proper burial with identification.

The most earnest effort to find missing Civil War soldiers, however, came not from the military or the government but from Clara Barton. Famous for founding the American Red Cross, Barton, who had also been the country’s first battlefield nurse, was perhaps the nation’s best known woman in the immediate after-math of the war. With President Lincoln’s blessing, and very limited congressional funding, she began the Office of Correspondence With Friends of the Missing Men of the United States Army inside her own living quarters in a boardinghouse on the corner of Seventh Avenue and E Street, NW, in Washington, D.C.—and thus became the first female to head a federal agency.

A one-woman operation, Barton’s effort would change the manner in which soldiers who had disappeared in war were handled by the United States military (among other things, she began labeling soldiers with their personal information, a practice that would result in dog tags by the turn of the century). More than 60,000 letters passed through her little office before it closed in 1868, and Barton not only answered more than 44,000 of these inquiries but also helped locate and identify 22,000 missing Civil War soldiers, most of whom had perished from wounds or disease.