A representative of the Vietnam War at the Tomb of the Unknowns at Arlington National Cemetery is gone, probably forever.

Some of the remains formerly there were identified last year through DNA testing as belonging to Air Force 1st Lt. Michael J. Blassie, and they were returned to his family for reburial. And several weeks ago, Defense Secretary William S. Cohen approved a Pentagon recommendation that the crypt reserved for a Vietnam serviceman remain empty because advances in DNA testing make finding another unknown unlikely.

Now, a new exhibit at a military medical museum in Washington is trying to fill a little bit of the void by explaining how it all happened.

The exhibit at the National Museum of Health and Medicine is called "Naming the Vietnam Unknown: Michael Joseph Blassie Comes Home." It explains the science of DNA testing, the role of the Armed Forces Institute of Pathology at Walter Reed Army Medical Center in solving the mystery, and the story of Michael Blassie.

Blassie, 24, was flying an A-37 when he was shot down over An Loc, about 60 miles north of Saigon in South Vietnam, on May 11, 1972. Although the military initially suspected that some remains discovered near An Loc were those of Blassie, the remains eventually were classified as unknown because of a lack of corroborating information.

President Ronald Reagan presided over an emotional Memorial Day ceremony in which the remains were interred in the Tomb of the Unknowns.

But Blassie's family believed that the remains could be identified and for years pressed for a disinterment. After a lengthy debate and a review of the case, Cohen ordered an exhumation last year.

On May 14, 1998, the Tomb of the Unknowns was opened, and after a solemn ceremony, the remains, consisting of six bones, were removed for DNA sampling. Forensic scientists at the Armed Forces Institute of Pathology (AFIP) studied the remains and took samples for DNA testing. Further study at the Armed Forces DNA Identification Laboratory in Rockville established that the remains were Blassie's.

"This particular exhibit demonstrates how the AFIP sets the gold standard in DNA identification," said Adrianne Noe, director of the museum.

Blassie was reburied with full military honors in Jefferson National Cemetery in Missouri, where his father is also buried.

The new exhibit has the blessing of the Blassie family. "It is a privilege for my brother's story to be part of this very important display because research matters to the Blassie family," said Pat Blassie, the pilot's sister. "If it wasn't for the work of the scientists at the AFIP, my family's claim that it was Michael Blassie in the Tomb of the Unknowns would still be questioned today."

The exhibit includes items that were found with Blassie at the crash site and were interred with him in the Tomb of the Unknowns. Artifacts include fragments of Blassie's Air Force flight suit and holster, remnants of his parachute and identification tag chain, an ammunition pouch and a signal marker and fire starter.

Also included are the flag used to drape Blassie's casket, as well as his ribbons, medals and Purple Heart.

The National Museum of Health and Medicine was founded as the Army Medical Museum in 1862 to study and improve medical conditions during the Civil War and is now a division of AFIP. The free museum is open daily except Christmas and is at Walter Reed Army Medical Center.

Reaching the End of the Road

Battered but unbent, four local Marine officers finished a month-long running and bicycling journey across the United States on Sunday afternoon at--appropriately enough--the Iwo Jima Memorial.

The team was greeted with a champagne spray by a crowd of several hundred family members, colleagues, friends and well-wishers. To get there, the officers had to survive the Mojave Desert, bicycle accidents, an unrelenting 100-miles-per-day pace, and, at the end, the mountains and humidity of Virginia.

The idea was the brainchild of Maj. Mike Monroe, a Marine stationed at Quantico working at the Officer Assignment Branch. Monroe was inspired by the example of a colleague who had skied across Iceland to raise money for charity.

Monroe came up with the idea of biking and running across America to raise money for the Children's Hopes and Dreams Foundation, a charity that fulfills the last wishes of terminally ill children and supports their families.

Monroe talked three friends into joining him: Maj. Mark Johnson, a colleague at the Officer Assignment Branch; Maj. Stu Helgeson, an infantry officer on the staff of the U.S. Naval Academy; and Maj. Art Bornschein Jr., an engineer at Marine Corps Systems Command in Quantico.

They dubbed their journey "The Mission" and trained for a year before setting off June 1 from El Toro Marine Corps Air Station in the Southern California desert.

"The first couple of days, there was a little bit of self-doubt going on," Johnson said.

The team soon achieved a rhythm, biking 90 miles and running 10 miles a day. But Johnson was knocked out of action midway through the trip when the team had a bicycle pile-up in Kansas. Johnson went flying over his handlebars and hit the pavement, breaking his collarbone. But he remained with the team throughout the journey, riding in a support van and coordinating media coverage.

Although they crossed the entire country, the toughest terrain was back home in Old Virginia, team members said. The ride along the Blue Ridge Parkway and Skyline Drive had spectacular views.

"Unfortunately, the route was marked with more long climbs than I care to recall right now," Monroe wrote on the team's daily posting on its Web site. "In short, it was just plain hard and I mean it."

There was little rest for the weary, though. Johnson was back at the office Monday, and the others reported back Tuesday.

Contributions in the name of The Mission may be sent to the foundation at 280 Route 46, Dover, N.J. 07801.

Military Matters appears every other week. Steve Vogel can be reached at vogels@washpost.com via e-mail.