Defense Department records show that, on average, more than 5,600 soldiers have disappeared each year from their units and been termed deserters by the Pentagon. Yet few are charged with the crime, according to those familiar with the U.S. military justice system.

"How many do we charge? Hassoun. That's one in a long, long time. We just don't do it," said Maj. Doug Powell, a spokesman for the Corps. "It's extremely rare."

The Pentagon classifies thousands of soldiers as deserters, either because they leave their unit or they fail to report for duty. In 2003, nearly 5,000 soldiers in the Army, Air Force and Marines were administratively classified as deserters.

That number has been dropping since 2001, when more than 6,200 were designated deserters. The figures for 2004 were incomplete, and the Navy could not provide annual desertion totals.

However, labeling a soldier a deserter for administrative purposes is largely a bookkeeping measure, reflecting that the soldier failed to report for at least 30 days.

Being charged with desertion is rare. More often, soldiers who are apprehended or return to their unit are charged with being absent without leave (AWOL) or else their cases are handled administratively.

"The difference between desertion and AWOL is the intent to remain away permanently, and proving someone intended to remain away permanently is not easy," said retired Maj. Gen. Michael Nardotti, who was the Army judge advocate general from 1993 to 1997.

"You probably can count on both of your hands" the number of desertion charges filed in the past several years, Nardotti said.

Under the military's code of conduct, however, prosecutors can show desertion by proving that the accused soldier was trying to shirk hazardous duty. That probably will be the course of action the government takes with Hassoun, said retired Brig. Gen. David Brahms, staff judge advocate for the Marine Corps commandant from 1985 to 1988.

There have been a few high-profile desertion cases in recent months as some soldiers refuse to serve in Iraq.

In May, Staff Sgt. Camilo Mejia was sentenced to a year in prison for desertion after refusing to return to Iraq. Mejia claimed conscientious objector status after he said he saw Iraqi civilians killed and prisoners abused during his deployment.

And in September 2003, Marine Reservist Stephen Funk was acquitted of desertion, but convicted of being AWOL after refusing to report for duty in Iraq when his unit was activated. He served six months in prison and since his release has been an outspoken peace activist.

Marine prosecutors will begin presenting their case against Hassoun on Tuesday at a pretrial hearing at Camp Lejeune, the North Carolina Marine base, which is home to Hassoun's unit. The government alleges Hassoun, a translator in a Marine anti-terrorism unit, took his service pistol and a Humvee and disappeared from Camp Fallujah in Iraq on June 20. He was initially classified as a deserter, but the status was changed to captured after video surfaced a week later of a blindfolded Hassoun with a glinting saber above his head.

Hassoun was reported killed on July 3, but the group that claimed to have taken him captive said the reports were false and on July 8 Hassoun mysteriously appeared in Tripoli, Lebanon.

Hassoun has not spoken about the episode, except in a brief statement in July where he denied deserting his post, insisting he was captured and held against his will. After a five-month investigation by the Naval Criminal Investigative Service, Hassoun was charged with desertion and theft of military property.

At Hassoun's hearing next week, an investigating officer will hear the evidence presented by the prosecutor, Maj. Stephen Keane. The investigating officer will forward a recommendation to Hassoun's commanding officer, Brig. Gen. Mastin Robeson, who will decide whether to convene a court-martial or handle the matter administratively, which could take several weeks.

The Naval Criminal Investigative Service is continuing to investigate what happened to Hassoun from the time he left the military base until the time he mysteriously appeared in Lebanon. That case would determine if any classified information was divulged.

That inquiry may take some time because of the demands on the intelligence agencies involved.