The tale of Robert Garwood is an embarrassment to the Marine Corps and a mystery to the American public. If all the allegations are true, how is it possible that one of the Marines' "few good men" could have put on an enemy uniform, led Viet Cong troops in battle against his former buddies and directed the interrogation of American prisoners of war?

And given the charges against Garwood, how is it possible that the Marine Corps has already ruled out the death penalty for treason in time of war?

What most Americans don't know is that the level of desertion in the Vietnam War zone was unprecedented in U.S. history. Thousands of deserters disappeared into the Saigon underworld. According to military sources, as many as 500 American GIs actively assisted the enemy in Vietnam. About 30 prisoners of war went over to the enemy and played active anti-American roles in the POW camps.

And as many as six Americans are believed to have taken up arms against U.S. troops in Vietnam. At least two of these -- both Marine privates -- are known to have joined in combat with the Viet Cong against American forces. Yet these two men now live in the United States, unpunished, under new identities furnished by the government itself.

A Pentagon spokesman said there were "no records" to indicate that any former American soldier took up arms against U.S. troops in Vietnam. Therefore, he implied, there cannot be any such soldiers now living in the United States, unpunished, under new identities.

In fact, many of the GI deserters were repatriated, with virtually no questions asked, during the frantic final hours of the American evacuation of Vietnam in 1975. They got off scot-free, perhaps in exchange for information considered valuable by the government -- or possibly because their sheer number would have been too staggering an embarrassment to warrant courts-martial.

Was it simply Garwood's poor timing -- turning up years after the war was over -- that got him in his present predicament? Or was his record particularly heinous?

From the Garwood story, as told to my reporter Lisa Krieger by sources close to the case, the reader can judge what, if any, special circumstances might set him apart.

Garwood was a shy, troubled highschool dropout when he joined the Marines at 17. Whether he chose the military as an escape from family problems or in hopes of fulfilling boyish fantasies, he soon became disillusioned. He wound up in Okinawa, where he asked to be sent home.

Instead, he was shipped to Vietnam, apparently branded as a troublemaker. His sergeants kept on his back incessantly. Still, he was given a fairly soft assignment: driving a jeep at the Danang military base.

According to a governlment source, Garwood became increasingly disillusioned with the military, and sought solace in the arms of a Vietnamese prostitute. He became friendly with a number of Viet Cong sympathizers, who nurtured doubts in his mind about the U.S. presence in Vietnam.

One day, on a trip into town, Garwood disappeared. One source says his jeep was later found buried, pocked with bullet holes; others say he sold it on the black market. In the government's version, Garwood survived by stealing food, cigarettes, liquor and luxury items to sell in the Vietnamese underworld.

Eventually, he wound up with the North Vietnamese. He was issued a uniform and a rifle and was given command of a combat patrol, a government source alleges.

Garwood was identified as a guard and interrogator at a North Vietnamese POW camp. American prisoners watched him strut around in his enemy uniform, living in relative comfort while they struggled for survival.

Garwood's own version of events during his 14-year absence is different. According to a close friend, he was captured in a hail of gunfire and taken prisoner. He remained a captive until he managed to escape from a forced labor camp in the jungle years after the war was over.

He never sympathized with the enemy, this source claimed. If he was seen in North Vietnamese uniform, carrying a gun, it was only because he was forced to in his role as a Viet Cong pack animal. The only time he ever attacked an American was when he punched a fellow prisoner in frustration. "He'd never hurt anyone," the source said. "He's the gentlest man I know."

Garwood's supporters say the Pentagon is embarrassed by Garwood's reappearance after all American POWs had been officially declared returned. r

"In 1973, when the Vietnamese said he was staying voluntarily, why didn't [U.S. authorities] demand to see him?" asked Garwood's friend. "The question is: Who deserted whom? He didn't desert the United States -- the United States deserted him. Bobby really loves this country. And this really hurts."