The chatter about Army Sgt. Bowe Bergdahl has been unrelenting ever since the White House announced Saturday that it had swapped five members of the Taliban in detention for the only U.S. service member held by the enemy in Afghanistan.

The buzz isn’t just because Bergdahl had been held in captivity since going missing in Afghanistan on June 30, 2009. It’s because it is widely believed that he walked off his base in a war zone with no plans to return. Doing so would be desertion, a crime in the military in which individuals leave their unit with no plans to return, or quit to avoid hazardous duty or “important service.”

Army Secretary John McHugh acknowledged the desertion concerns about Bergdahl on Tuesday, but added that the Defense Department will take “as long as necessary” to help him recover medically from his time in captivity.

“The Army will then review this in a comprehensive, coordinated effort that will include speaking with Sgt. Bergdahl to better learn from him the circumstances of his disappearance and captivity,” McHugh said in a statement. “All other decisions will be made thereafter, and in accordance with appropriate regulations, policies and practices.”

Desertion in itself is not uncommon. Thousands of U.S. service members did so annually during the height of the Iraq war, according to numerous media reports. Those individuals typically deserted while in the United States, however, either before their unit deployed, or while they were home on leave in the middle of a deployment. Many of them sought refuge in Canada, like Kimberly Rivera, an Army private who was sentenced last year to 10 months in prison for fleeing in 2007 from a break in a deployment to Iraq.

What makes Bergdahl’s case so unusual in modern times is that he disappeared while in a war zone. There are remarkably few known cases in recent years in which service members have been accused of fleeing their units while deployed.

Perhaps the most famous case is that of Marine Cpl. Wassef Ali Hassoun, who disappeared June 19, 2004, from his base in Fallujah, Iraq. Several media reports suggested the following month that he had been killed after being held captive, but he later resurfaced at the U.S. Embassy in Lebanon, where he had family. That reportedly came after members of his family traded gunfire in northern Lebanon with another family who had taunted him and his relatives for their ties to the U.S.

In December 2004, Hassoun was charged with desertion. He denied the accusations, but then disappeared again the following month after visiting family in Utah. Little was heard from him again until 2011, when his family reached out to a publicist in Los Angeles seeking a $1 million book and movie deal, according to an Associated Press account at the time. The publicist told the AP that Hassoun’s brother said the missing Marine was living in Lebanon with family.

Another famous case of a service member who went missing abroad is Air Force Maj. Jill Metzger. She disappeared while on an approved shopping trip in Bishkek, Kyrgyzstan, in 2006, sparking a nationwide search before she reappeared three days later in a town 20 miles away, saying she had been kidnapped.

Defense officials told ABC News at the time that inconsistencies in her story raised questions whether she actually was running away from a recent marriage. She returned to active duty in 2010, however, after the Air Force Times reported that she had taken an 18-month medical leave. The Air Force released the results of its investigation in 2012 following a series of online reports that questioned her motives, saying it found she was kidnapped and had escaped after stabbing one of her captors. She was never charged with a crime.

The lack of recent deserter cases by U.S. service members while abroad contrasts with previous wars. In World War II, for example, some 50,000 U.S. troops deserted in the European theater, according to the 2013 book “The Deserters.” Most of those who deserted broke down in combat, and some returned to duty voluntarily without any concerns being raised, the author, Charles Glass, told NPR.

One of the most famous deserters is Pvt. Eddie Slovik, who ran from combat duty in France in 1944 while deployed with the Army’s 28th Infantry Division. He acknowledged deserting in a written confession in October of that year — something that ultimately sealed his fate.

Slovik was shot by a 12-man firing squad after Gen. Dwight Eisenhower, later president of the United States, refused his appeal for leniency and made an example of him. He is still the last U.S. service member to be executed for deserting, and was memorialized in a 1974 TV special starring Martin Sheen. The seminal scene:

Deserters also disappeared in Vietnam. In one case, a Marine by the name of Douglas Beane who vanished in 1969 was arrested in Australia in 1986, according to an AP report. He later said in interviews that he disappeared after watching a fellow Marine go on a rampage in their camp, killing two U.S. service members and wounding three others. The Los Angeles Times reported that he had nine children with four women in Australia while roaming the countryside using false names, and turned himself in because he wanted to end his life on the run and visit his sick father in Vermont.

Like many other deserters, Beane got off relatively easily. He admitted to all charges in a hearing at Quantico, Va., and accepted an other than honorable discharge. Still, he said in a 1987 interview that he does not consider himself a deserter.

“As far as I’m concerned, I did my time there. . . . ” he told the Times. “I’ve suffered enormously for 17 years. I wasn’t living a standard life. I was in exile. I was a man without a country. It was hell.”