UNDATED - In this undated image provided by the U.S. Army, Sgt. Bowe Bergdahl poses in front of an American flag. U.S. officials say Bergdahl, the only American soldier held prisoner in Afghanistan, was exchanged for five Taliban commanders being held at Guantanamo Bay, Cuba, according to published reports. Bergdahl is in stable condition at a Berlin hospital, according to the reports. (Photo by U.S. Army via Getty Images) Army Sgt. Bowe Bergdahl poses in front of an American flag. U.S. officials say Bergdahl, the only American soldier held prisoner in Afghanistan, was exchanged for five Taliban commanders being held at Guantanamo Bay. (credit: U.S. Army via Getty Images)

WASHINGTON (CBSDC/AP) — A soldier claims that he was told by his chain of command to not say anything about Army Sgt. Bowe Bergdahl walking off an Afghan base in 2009.

Retired Army Spc. Josh Fuller told Fox News Wednesday that he was told to keep quiet about Bergdahl leaving his post and getting captured by the Taliban.

“We had all known that he had deserted his post and there was never anything about him getting captured or a POW until a little while later when it came down from the chain-of-command that we needed to keep quiet about it, not say anything and that we’re going with the narrative that he’s captured,” Fuller told Fox News.

Fuller, who stated that Bergdahl pretty much kept to himself and didn’t socialize with other soldiers, said that attacks on the base increased after Army sergeant left.

“Whenever he went and walked off the base, only stuff that we know, that we trained for, that the sports that we know on vehicles, how are moves are, stuff like that, they were getting hit very precisely,” Fuller explained to Fox News.

“And the ambushes we used, the certain tactics that we used, the Taliban was picking up on those things and the Haqqani network started using the same things as well.

“So they were very precise and very accurate. You could tell it was somebody on the inside that had that info.”

Since Bergdahl was exchanged for five high-level Taliban members who were detainees at Guantanamo Bay, reports have surfaced that at least six U.S. soldiers were killed searching for him.

Matt Vierkant, 27, a team leader of another squad in Bergdahl’s platoon, told The Associated Press that soldiers from his unit and other units were wounded or killed on missions to chase down leads related to Bergdahl.

He said Bergdahl’s fellow soldiers knew within five or 10 minutes from the discovery of disappearance that he had walked away. In retrospect the signs were there, he said, but there was nothing so definitive that would have prompted action.

“He said some strange things, like, ‘I could get lost in those mountains,’ which, at the time, that doesn’t really strike you as someone who is going to leave their weapon and walk out.”

Vierkant said he believes it’s paramount that an investigation determine whether Bergdahl deserted or collaborated with the enemy.

“It shouldn’t even be a question of whether, it should question of when,” he said.

U.S. Joint Chiefs Chairman Gen. Martin Dempsey said Tuesday that the Army may pursue desertion charges against Bergdahl.

Bergdahl disappeared on June 30, 2009. A Pentagon investigation concluded in 2010 that the evidence was “incontrovertible” that he walked away from his unit, said a former Pentagon official who has read it.

The military investigation was broader than a criminal inquiry, this official said, and it didn’t formally accuse Bergdahl of desertion. In interviews as part of the probe, members of his unit portrayed him as a naive, “delusional” person who thought he could help the Afghan people by leaving his Army post, said the official, who was present for the interviews.

Nabi Jan Mhullhakhil, the provincial police chief of Paktika province in Afghanistan, where Bergdahl was stationed with his unit, said elders in the area told him that Bergdahl “came out from the U.S. base … without a gun and was outside the base when he was arrested by the Taliban.”

After weeks of intensive searching, the military decided against making an extraordinary effort to rescue him, especially after it became clear he was being held in Pakistan under the supervision of the Haqqani network, a Taliban ally with links to Pakistani’s intelligence service.

Nonetheless, individual units pursued leads as they came in. The Pentagon official familiar with the talks said, “I know for a fact that we lost soldiers looking for him.”

But the Pentagon maintained the circumstances of his capture were irrelevant.

“He is an American soldier,” Rear Adm. John Kirby said. “It doesn’t matter how he was taken captive. It doesn’t matter under what circumstances he left. … We have an obligation to recover all of those who are missing in action.”

During a press conference Tuesday in Poland, President Barack Obama defended his decision to exchange the detainees for Bergdahl.

Regardless of the circumstances, whatever those circumstances may turn out to be, we still get an American soldier back if he’s held in captivity,” Obama said. “We don’t condition that.”

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