Prior to his release in December, Abdul Hafiz was Prisoner Number 1030 at Guantanamo Bay. Now, less than four months later, he's back home in Afghanistan and working for the Taliban -- just the latest of more than 100 released detainees who have returned to terrorism, according to the Pentagon.
Hafiz, suspected in the March 2003 kidnapping and murder of an International Red Cross worker, was the "Taliban head of all Madrassas ... responsible for recruiting and sending young men to fight for the Taliban," according to U.S. government memos. He was said to have maintained contacts for Mullah Mohammad Omar, the leader of the Taliban of Afghanistan, and to have admitted to participating in jihad against the Soviets.

But despite the list of charges against him, the U.S. government transferred Hafiz to his home country in December. And now, a senior U.S. official tells Fox News, he is back on the battlefield. According to a published report, Hafiz has been appointed by Mullah Omar to oversee ransom demands for kidnapping victims and to coordinate with nongovernment-aid organizations operating in the Taliban's areas of influence.
That makes Hafiz just the latest addition to an increasingly long list of former Guantanamo detainees suspected to have returned to terror. The Pentagon, in an estimate issued in January, now believes that roughly 20 percent of the 560 detainees who were released from Guantanamo are back on the terror front lines.
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The figure, which was echoed in a Feb. 1 letter from President Obama's chief counterterrorism adviser, John Brennan, to House Speaker Nancy Pelosi, is a nearly 50 percent increase from the Pentagon's estimate of 14 percent last April, and nearly double the 11 percent estimate issued in January 2009.
And though the current estimate is higher than ever, it's still a "low-ball" one, says Lt. Col. Jeff Addicott, a former Green Beret and judge advocate general and director of the Center for Terrorism Law at St. Mary's University.
"I'd say the figure is probably closer to 30 to 40 percent," Addicott told FoxNews.com. "A lot of these folks go underground, they change their name, they hide out a little bit, they pop back up."
Addicott says part of the problem is the push to rehabilitate enemy combatants who can't be rehabilitated.
For example, a "rehabilitation" center in Saudi Arabia that has become home to many released detainees claims it can turn around detainees' radical beliefs in a matter of months. But two of its graduates, former Guantanamo detainees Ibrahim Sulayman Muhammad Arbaysh and Abu Sufyan al-Azdi al-Shahri, now lead Al Qaeda in the Arabian Peninsula -- the Yemeni group that has claimed responsibility for the failed Christmas Day bombing of a U.S. airliner and is being linked to a recently foiled plot against key oil and security facilities in Saudi Arabia.
"That's out of the playbook of Al Qaeda," Addicott said. "They tell people, 'If you're captured, claim that your tortured. If that doesn't work, if you have an opportunity to be rehabilitated, use that to get out. So many of them play this game and they know the buttons that they can push."
In reality, Addicott says, the chances of "rehabilitating" a jihadist are slim to none.
"We're bending over backwards, we're wishing, we're hoping, we're trying to believe them, we're trying to rehabilitate them, but these guys are motivated by a cult-like religious ideology and it's real hard to rehabilitate people in that type of system," he said.
The military acknowledges there are "inherent risks" in releasing detainees,
"The U.S. government works to ensure that Guantanamo transfers are conducted in a manner that takes into account concerns about threat mitigation and security, irrespective of the country to which they are sent," Maj. Tanya J. Bradsher, a Pentagon spokeswoman, said.
But in some cases, says Wayne Simmons, a terrorism analyst and former CIA operative, the U.S. is even forking out big money to rehabilitate combatants physically, only to later see them use it to their advantage.
"When we saw the medical attention they got, it was incredible," Simmons said of his visits to Guantanamo Bay. "These guys come in wounded, they take care of their wounds. No limbs? We give them brand new prostheses. Turn them loose, guy goes home, picks up arms and uses that leg to help kill us."
That's what happened in the case of Abdullah Mehsud, says Brig. Gen. Jay Hood, who runs the detention center.
"He came to us without one leg from about the knee down; we fitted him with a prosthetic leg before he left while in U.S. custody," Hood told a House panel in 2005.
The artificial limb was reported to have cost American taxpayers between $50,000 and $75,000, but it was nowhere near what Mehsud, a.k.a. Said Mohammed Alim Shah, cost the Pakistani people in April 2007, after his release. Pakistani officials say he directed a homicide attack that killed 31 people. Two months later he blew himself up to avoid capture by Pakistani forces.
Addicott says these cases show that the U.S. needs to show more discretion when determining whether to release the prisoners at Guantanamo.
"We need to realize that they have a motivation to lie and they're enemy combatants; we need to do a screening process that's much more demanding," he said.
Simmons says that pushing to try many of these prisoners in civilian courts shows the U.S. government is moving in the opposite direction.
"We capture them, bring them into detention, we hold onto them, the ACLU steps up and gets them out of jail and turns them loose," Simmons told FoxNews.com. "All of a sudden they're criminals. They're not criminals ... they're enemy combatants."
Addicott says that the problem now is that "at Gitmo, where we have around 170 now, we can only charge about 50 with crimes via military commissions. The remaining cases do not have enough evidence to charge them with a crime, but they are truly too dangerous to release."
"I've been there," he says. "These are the hard core. They don't bring that rehabilitation game. They scream, and yell, and throw feces at our guards, saying, 'We're gonna kill you, we're gonna kill you.'"
These people, Addicott says, must be kept at Guantanamo indefinitely.
But Jonathan Hafetz, an attorney for the ACLU's National Security Project, says doing so will only make matters worse.
"Detaining people without charge undermines our security by zapping our counterterrorism policies of their necessary legitimacy," Hafetz told Foxnews.com. "It creates animosity against the United States and hurts our efforts to build the support for counterterrorism policies in the communities and the countries where that support is essential."
Hafetz says if the government has enough evidence to conclude that someone is too dangerous to be released, it should have enough evidence to convict them of a crime -- and having to prosecute them in a civilian court would lead to better intelligence.
"If you're not forced to develop your case, you can detain without ever having to defend your case; it leads to sloppy intelligence-gathering, a lot of false positives, detaining people who should be detained," Hafetz said. "It's far more effective to be detaining people with the intent that you're going to have to put on evidence in court.
"You gather more information, you help ensure that the information is reliable, and it forces you to make sure you're detaining the right people. And I think detaining the wrong people undermines our security, in addition to violating basic rights."
"Federal courts have successfully prosecuted more than 400 terrorists; military commissions have prosecuted only three," he said.
Addicott says there are safeguards in place to defend against detaining the "wrong people."
"Every person at Gitmo has the right to go to a federal judge and challenge their designation as an enemy combatant," he said.
One of those challenges recently resulted in an order to release suspected Al Qaeda organizer Mohamedou Ould Slahi, once called "the highest value detainee" at Guantanamo Bay, after a military prosecutor determined "special interrogation" methods used on him amounted to torture, rendering evidence they produced inadmissible in trial.
"They've got more due process rights than any enemy combatant in the history of war has ever had," Addicott said. "That's enough for me."