By Mick Krever, CNN

The man who opened up the Guantanamo Bay Prison now says he wants to see the facility closed.

U.S. Major General Michael Lehnert (retired), first commander of the Guantanamo Bay Prison, told CNN’s Christiane Amanpour that terrorists were “successful” in changing America.

“The objective of terrorism is to change the nature of their adversary,” he said. “And I would opine that they've been successful. They've changed the way we've acted, they've caused us to walk away from the Constitution, and they've caused us to act as if we were afraid.”

Closing Guantanamo Bay was President Barack Obama’s signature promise during the 2008 campaign; he even signed an executive order to that effect.

But it never happened.

About 160 prisoners remain trapped without charge in Guantanamo's legal limbo, even though 82 have been cleared for transfer to their home country.

Following a hunger strike this year by more than 100 prisoners, President Obama again kicked this issue into high gear.

And even Congress is for the first time voting to loosen some restrictions on transferring prisoners.

“It looks right now that we have probably our best chance in a decade to close Guantanamo,” Lehnert said.

He attributed that change to three things: The twilight of U.S. military operations in Afghanistan, President Obama’s concern for his legacy, and bipartisan support in Congress.

“We need to move forward; we need to say that the Constitution doesn't stop at our water's edge and that we need to close Guantanamo.”

Opponents of the plan to transfer those detainees that have been cleared say that the former prisoners would commit, or recommit, themselves to terrorism.

No plan to release detainees is “zero risk,” Lehnert conceded. “But we do believe that that risk can be managed.”

“We have the best military in the world; we have very clear biometrics on these individuals.”

And with the prisoners still in custody, the U.S. has “the opportunity to let them know that if they decide to revert back to their old ways, then we're going to find them – and our military is good enough to do that.”

Lehnert was there in the very first days of the Guantanamo Bay Prison; originally, he said, he thought it would be open for only a short time.

“But as I was down there, by about the second month, I realized that we were going to be in for the long haul,” he said. “I also began to recognize that many of the individuals that had been sent to me probably never should have been sent there in the first place.”

The act of holding someone prisoner while often “a very necessary act” is also “soul-deadening” for the jailer, he said.

It is for that reason, he told Amanpour, that he committed himself to following the Geneva Conventions – that despite the fact that his civilian boss at the time, Secretary of Defense Donald Rumsfeld, claimed that the document did not apply to prisoners at Guantanamo because they were not prisoners of war, but rather “unlawful combatants.”

“History's going to judge whether or not he was wrong,” Lehnert said of Rumsfeld.

“There really wasn't much other policy” at the time, he said, and the Geneva Conventions were “a very good and sound document that would allow us to at least have a road map for how we would operate.”

If the Guantanamo Bay prison is indeed shuttered, it may be a monetary argument, not a moral one, that is the final straw.

Indeed, Guantanamo Bay is the most expensive prison on earth.

“The American taxpayers are paying $2.7 million per prisoner, per annum” at Guantanamo Bay, he said. “Now to juxtapose that, a Supermax prison in the United States costs, at the high end, $78,000 per prisoner.”

But the individual motivation of congressmen does not much concern Major General Lehnert.

“For some, it's the money; and for some, it's the moral issue. Personally, I don't care what motivates them as long as it motivates them to move towards closure of Guantanamo.”