Part of his plan, he explained, was to release many of the 91 prisoners then still held there.
"First," he said, "we'll continue to securely and responsibly transfer to other countries the 35 detainees -- out of the 91 -- that have already been approved for transfer."
Another part was to release even more prisoners than that.
"Second, we'll accelerate the periodic reviews of remaining detainees to determine whether their continued detention is necessary," he said.
"And if certain detainees no longer pose a continuing significant threat, they may be eligible for transfer to another country as well," he said.
What is the difference between a terrorist who poses a "threat" and a terrorist who poses a "significant threat?"
Two weeks after Obama's speech, Director of National Intelligence James Clapper released a legally mandated report citing "the number of individuals formerly detained at Naval Station, Guantanamo Bay, Cuba, who are confirmed or suspected of returning to terrorist activities after release or transfer from such Naval Station."
The report said the U.S. had confirmed that 118 of the 676 total detainees that had been released from Gitmo up to that point had returned to terrorist activities. The U.S. also suspected another 86 of having done so.
That means the U.S. confirmed or suspected 30.2 percent of all released Gitmo detainees had returned to terrorist activities.
The report also noted that of the 144 Gitmo detainees released since Jan. 22, 2009 (two days after Obama took office), the U.S. had confirmed that 7 had returned to terrorist activities and suspected 12 others.
That means the U.S. has confirmed or suspects that 13.2 percent of the Gitmo detainees released under Obama have returned to terrorist activities.
What about the detainees the U.S. still held at Gitmo as of March? Would some of these also return to terrorism if released?
"Based on trends identified during the past eleven years, we assess that some detainees currently at GTMO will seek to reengage in terrorist or insurgent activities after they are transferred," said the DNI's report.
"While enforcement of transfer conditions may deter reengagement by many former detainees and delay reengagement by others, some detainees who are determined to reengage will do so regardless of any transfer conditions, albeit probably at a lower rate than if they were transferred without conditions," said the DNI's assessment.
When detainees released from Gitmo return to terrorism one consequence is dead Americans.
A month after Obama's speech, Paul Lewis, the Defense Department's special envoy for Guantanamo closure, testified in the House Foreign Affairs Committee.
Republican Rep. Dana Rohrabacher of California asked him an obvious question: How many people had released detainees killed?
Lewis said: "I can talk about that in a classified setting, but--"
Rohrabacher interrupted: "Oh, classified?"
"Yes," said Lewis.
"So, is it over 10?" asked Rohrabacher.
"Sir," said Lewis, "what I can tell you is, unfortunately, there have been Americans that have died because of Gitmo detainees."
Last week, Republican Sen. Kelly Ayotte of New Hampshire released another legally mandated report that the Department of Defense had stalled in giving to her. It lists the 107 people still detained at Guantanamo as of last November and summarizes their "background."
On Monday, the Department of Defense announced that 15 Gitmo detainees had been transferred to the United Arab Emirates.
"The terrorists this administration just released include individuals who fought on the frontlines against U.S. and other coalition forces, targeted U.S. personnel with explosives, served as bin Laden bodyguards, and acted as al Qaeda IED experts," Sen. Ayotte correctly noted -- based on the DOD report -- about these newly released detainees.
As Obama explains it, releasing Gitmo detainees and closing the prison serves both fiscal and national security interests.
"And let me point out that the plan we're submitting today is not only the right thing to do for our security, it will save money," he said in his February speech.
"The Defense Department estimates that this plan, compared to keeping Guantanamo open, would lower costs by up to $85 million a year," he said. "Over 10 years, it would generate savings of more than $300 million."
President Obama said nothing about the released detainees who had returned to terrorism -- or the Americans who died because of it.