Since Army Sgt. Bowe Bergdahl was captured in the mountains of Afghanistan in 2009, his father had become an expert on Guantanamo Bay’s detainees. It was out of necessity, because the Taliban demanded that the United States free prisoners from Guantanamo in exchange for Bergdahl.

“No family in the United States understands the detainee issue like ours,” Robert Bergdahl said in a 2011 plea to his son’s captors.

So it wasn’t entirely unusual when Bergdahl apparently published a tweet last week about Guantanamo’s detainees. Except this tweet was directed at a Taliban spokesman. And it came just four days before it was announced that his son was finally being released.

“I am still working to free all Guantanamo prisoners,” the tweet said, according to various screen grabs. The tweet was subsequently deleted. “God will repay for the death of every Afghan child, ameen.”

The elation over the release of America’s only prisoner of war has mixed with questions about the circumstances of his disappearance — and the cost of his return.

The recent tweet has only fanned those flames in some quarters.

“Folks, this is either a very bad case of Stockholm Syndrome or something far more nefarious is at stake,” wrote West, a popular conservative activist. “Regardless, there is more to this than meets the eye of Obama making a unilateral decision and announcement on a Saturday — when he believes no one is watching.”

Bergdahl’s critics view the tweet as another demonstration of the father’s and son’s contempt for their own country. But the elder Bergdahl’s Twitter feed — @bobbergdahl — tells a more nuanced story.

In addition to calling for the release of Guantanamo detainees, Bergdahl also tweeted in solidarity with a a host of prisoners elsewhere, including abducted journalist James Foley, who was detained in Syria; Saeed Abedini, an American Christian pastor jailed in Iran; and Kenneth Bae, an American jailed in North Korea.

Bergdahl has also used Twitter to stay in constant contact with his son’s supporters and sympathizers, tweeting often about his son and sharing articles about the war in Afghanistan interspersed with a few anti-war links and videos.

It’s unclear why this particular tweet was deleted: A spokesman for the family told The Post on Monday that Bob and Jani Bergdahl were asked by the media about the now-missing message upon their return to Idaho from Washington. But the Bergdahls didn’t discuss it.

“They just nodded their head in acknowledgement of the question, but they didn’t address [it] in their remarks,” said Col. Timothy Marsano, the family spokesman.

During their long, painful wait for their son’s safe return, the Bergdahls have vacillated between quiet, consistent remembrance and outspoken activism.

After his son’s capture, Bergdahl appeared to pour himself into an effort to find solidarity with his missing son. He grew a long beard and learned Pashto and Urdu, languages spoken along the Afghan-Pakistan border.

And it has been no secret that he offers compassion to his son’s captors.

The father of former prisoner-of-war Bowe Bergdahl recorded this personal message to the Pakistani armed forces, citizens, and his son's captors in 2011. (Robert Bergdahl via YouTube)

“Strangely to some we must also thank those who have cared for our son for almost two years,” Bergdahl said in the 2011 video message to the Taliban. “We know our son is a prisoner and at the same time a guest in your home.”

Last year, during a rally hosted by the P.O.W. activist organization Honor-Release-Return, Bergdahl commented that the Taliban treated his son “fairly.”

“Bowe and the other Americans in captivity have been extremely fortunate not to be badly mistreated by the Taliban,” he said, referring to other unnamed Americans in captivity, as he often does.

At times during the last five years, he considered taking matters into his own hands. He thought about going to Pakistan to retrieve his son himself.

“I’ll talk to them,” he told Rolling Stone Magazine in a 2012 profile. “I’ll bring him home myself.”

And he has said he maintains constant e-mail contact with a Taliban member with knowledge of his son’s whereabouts.

When negotiations stalled in 2012, the Bergdahls spoke out forcefully in favor of the exchange of Guantanamo prisoners for their son, in an interview with the Idaho Mountain Express — even while they praised the U.S. government’s handling of the situation.

Mr. and Mrs. Bergdahl … are advocating that the Pentagon and the White House consider swapping one or more U.S. prisoners being held at Guantanamo Bay, Cuba, for their son.
“I’m pushing it hard,” Mr. Bergdahl said. “We started out by trying to encourage the Taliban to take care of our son. … Now, we’re worried that the government isn’t concerned enough to put him on the (negotiating) table.” …
Mr. Bergdahl said he believes a deal to swap Taliban prisoners at Guantanamo for Bowe would be a “win-win” for the United States—his son could be returned safely to Idaho and the government could foster goodwill with the Afghan people.

After five years of waiting, the U.S. finally did.

In exchange for the release of U.S. Army Sgt. Bowe Bergdahl, the U.S. agreed to free five Taliban commanders from Guantanamo Bay. (Tom LeGro and Natalie Jennings/The Washington Post)