Obama, realizing how high emotions run on detainee treatment during the Bush administration and now, made it a point to personally explain his change of heart, stopping to address TV cameras late in the day as he left the White House for a flight to Arizona.
He said the photos had already served their purpose in investigations of "a small number of individuals." Those cases were all concluded by 2004, and the president said "the individuals who were involved have been identified, and appropriate actions have been taken."
Obama's reversal on the photo release set off immediate reactions from bloggers, liberals who decried that he was buckling to political pressure and conservatives who agreed with the decision but said it proved Obama was a flip-flopper.
One Huffington Post blogger called the decision "a terrible mistake" and declared that Obama had buckled under pressure from former Vice President Dick Cheney.
When photos emerged in 2004 from the infamous U.S.-run Abu Ghraib prison in Iraq, showing grinning American soldiers posing with detainees -- some of the prisoners naked, some being held on leashes -- the pictures caused a huge anti-American backlash around the globe, particularly in the Muslim world.
The Pentagon conducted 200 investigations into alleged abuse connected with the photos that are now in question. The administration did not provide an immediate accounting of how they turned out.
"This is not a situation in which the Pentagon has concealed or sought to justify inappropriate action," Obama said of the photos. "In fact, the most direct consequence of releasing them, I believe, would be to further inflame anti-American opinion and to put our troops in greater danger."
The Justice Department filed a notice of its new position on the release, including that it was considering an appeal with the Supreme Court. The government has until June 9 to do so.
Obama said, "I want to emphasize that these photos that were requested in this case are not particularly sensational, especially when compared to the painful images that we remember from Abu Ghraib."
Still, he said he had made it newly clear: "Any abuse of detainees is unacceptable. It is against our values. It endangers our security. It will not be tolerated."
The effort to keep the photos from becoming public represented for many a sharp reversal from Obama's repeated pledges for open government, and in particular from his promise to be forthcoming with information that courts have ruled should be publicly available.
As such, it invited criticism from the more liberal segments of the Democratic Party, which want a full accounting -- and even redress -- for what they see as the misdeeds of the Bush administration.
"The decision to not release the photographs makes a mockery of President Obama's promise of transparency and accountability," said ACLU attorney Amrit Singh, who had argued and won the case in question before the 2nd U.S. Circuit Court of Appeals in New York. "It is essential that these photographs be released so that the public can examine for itself the full scale and scope of prisoner abuse that was conducted in its name."
Human Rights Watch called the decision a blow to transparency and accountability. On Capitol Hill, Republicans welcomed the change, however. A military group also said it was relieved.
"These photos represent isolated incidents where the offending servicemen and women have already been prosecuted," said Brian Wise, executive director of Military Families United.
The reactions were a reverse of what happened after Obama's decision last month to voluntarily release documents that detailed brutal interrogation techniques used by the CIA against terror suspects. Those also came out in response to an ACLU lawsuit, and his decision then brought harsh and still-continuing criticism from Republicans.
This time he's kicking the decision back into court, where his administration still may be forced into releasing the photos.
Indeed, there is some evidence that the administration has little case left.
White House spokesman Robert Gibbs said the president instructed administration lawyers to challenge the photos' release based on national security implications. He said the argument was not used before.
But the Bush administration already argued against the release on national security grounds -- and lost.
"It is plainly insufficient to claim that releasing documents could reasonably be expected to endanger some unspecified member of a group so vast as to encompass all United States troops, coalition forces, and civilians in Iraq and Afghanistan," the three-judge appeals panel wrote in September 2008.
The Justice Department had concluded that further appeal would probably be fruitless, and last month, Gibbs said the president had concurred with that conclusion, though without commenting on whether Obama would support the release if not pressed by a court case.
Thus, the administration assured a federal judge that it would turn over the material by May 28, including one batch of 21 photos and another of 23 images. The government also told the judge it was "processing for release a substantial number of other images," for a total expected to be in the hundreds.
The lower court also has already rejected another argument the president and his spokesman made, that the photos add little of value to the public's understanding of the issue. "This contention disregards FOIA's central purpose of furthering governmental accountability," the appeals court panel concluded in the same decision.
Obama's own Jan. 21 memorandum on honoring the Freedom of Information Act also takes a different line. "The government should not keep information confidential merely because public officials might be embarrassed by disclosure, because errors and failures might be revealed, or because of speculative or abstract fears," it said.
The president informed Gen. Ray Odierno, commander of U.S. troops in Iraq, of his decision during a White House meeting on Tuesday.
Gen. David Petraeus, the senior commander for both wars, had also weighed in against the release, as had Gen. David McKiernan, the outgoing top general in Afghanistan.
Military commanders' concerns were most intense with respect to Afghanistan. The release would coincide with the spring thaw that usually heralds the year's toughest fighting there -- and as thousands of new U.S. troops head into Afghanistan's volatile south.
Defense Secretary Robert Gates said he had once held the view that it might be best to "go through the pain once" and release a large batch of images now, since so many are at issue in multiple lawsuits. But he -- and the president -- changed their minds when Odierno and McKiernan expressed "very great worry that release of these photographs will cost American lives," Gates said before the House Armed Services Committee.
"That's all it took for me," Gates said.------
Associated Press writers Anne Gearan, Devlin Barrett, Lara Jakes and Pauline Jelinek contributed to this report.