GUANTÁNAMO BAY, Cuba — Four months to the day after the Sept. 11 attacks, a photographer hoisted a camera above shiny new razor wire and took a picture of 20 prisoners on their knees in orange uniforms, manacled, masked and heads bowed.

The image ignited a debate over what the United States was doing at its offshore prison, which continues operating to this day. It also became one of the most enduring, damning photos of U.S. detention policy in the 21st century.

But lost in time and collective memory to many is that the picture was not some leaked image of torture that the public was not meant to see. It was taken by a U.S. Navy photographer, intentionally released by the Defense Department.

“I was doing exactly what I was assigned to do,” said the photographer, Shane T. McCoy. “It was my job to document it. I absolutely had to photograph it. And I had to send it up.”

The date was Jan. 11, 2002. In Afghanistan and Pakistan, local allies had scooped up hundreds of suspected foreign fighters and Qaeda members and delivered them to U.S. forces. The C.I.A. had yet to establish its secret prison network. The detainee abuse scandal at Abu Ghraib prison in Iraq was years away.

And an Air Force cargo plane had delivered the first prisoners to the base in southeast Cuba — the “least worst place” for the mission, Defense Secretary Donald H. Rumsfeld said. Mr. McCoy, a petty officer at the time, drew the assignment of photographing opening day at Camp X-Ray for the elite Combat Camera unit.

In time, the United States would hold about 780 prisoners at the remote outpost. In a matter of months, after the first 300 prisoners were brought there, the Pentagon had put up crude rows of cells welded from shipping containers. Later, the military built air-conditioned prisons, where the last 39 detainees are held today.

To the chagrin of a succession of military commanders, the image of those first 20 men on their knees would not go away.

Newspapers and magazines routinely republish it in articles about the prison, the base and the United States’ war on terrorism. Protesters don orange and re-enact it. Islamic State fighters usurped it and put hostages in bright orange clothing, then executed them.

It has become so pervasive, so emblematic of U.S. detention policy that some do not realize that it was taken at Guantánamo Bay, the prison that the George W. Bush administration made its showcase detention operation.

In a recent episode of “60 Minutes” about a former National Security Agency contractor who leaked a government document, the Guantánamo photo that was released by the U.S. military filled the screen to illustrate the idea that the government has used classification “to conceal wrongdoing — torture in the war on terror for example.”

How you see that photo depends on “your politics, your awareness of Guantánamo and what went on there — on your capacity for empathy, whether or not anybody in your family has ever been in prison,” said Anne Wilkes Tucker, the former curator of photography at Houston’s Museum of Fine Arts.

“That picture will be interpreted and reinterpreted for probably ever,” she said. “It’s so rich, and can solicit 180-degree interpretations. From ‘We got them’ to ‘More than half are probably innocent.’”

Hours before the first 20 men arrived, the Marine responsible for setting up Camp X-Ray, Brig. Gen. Michael Lehnert, described them as “the worst of the worst” of the detainees held in Afghanistan. It would eventually be clear that was not true.

Just two are held today. Of those first 20, eight were released by the time Mr. Bush left office. None were ever charged in the Sept. 11 attacks.

In Senate testimony last month, Mr. Lehnert, who retired as a major general, called the enterprise he had set up misguided, at odds with U.S. values. He urged that it be closed.

Mr. McCoy, 47 and now a photographer for the U.S. Marshals Service, recalled that day as a long one. He had split the duties with another Navy photographer, and with a coin toss ended up documenting the men awaiting registration in a makeshift, open-air holding compound.

He chose about 100 images, wrote captions and sent them to Washington.

At the Pentagon about a week later, news organizations were clamoring for transparency at the nascent detention operation in Cuba. Grainy, night-vision news footage had been broadcast from Afghanistan showing U.S. soldiers leading prisoners in rags, with bags on their head.

“The challenge was that the Geneva Conventions specifically prohibit holding detainees up to public ridicule or humiliation,” Victoria Clarke, Mr. Rumsfeld’s spokeswoman, wrote in her 2006 memoir, “Lipstick on a Pig.” To “allay some of our critics,” she obtained permission and released five photos.

People in the Pentagon saw a portrayal of safely held, anonymous prisoners that met Geneva Conventions obligations to protect prisoners against “public curiosity.”

Out in the world, the imagery struck some people as cruel. They saw degradation, sensory deprivation and subjugation.

“Did I ever misread what was in those photos,” Ms. Clarke wrote. “Instead of showing the care and concern with which we treated the detainees, the photos served as high-octane fuel for our critics and doubters.”

Some in Europe were particularly offended. The dragnet in Afghanistan and Pakistan had rounded up English-speaking Muslims, some of them from Western Europe, and they were being sent to Guantánamo Bay.

“Shaved and Confused,” said a headline accompanying the photo in Glasgow’s Sunday Herald. “Even Our Enemies Have Human Rights,” declared London’s Sunday Independent. “Guantánamo Scandal,” said the title of a blurb on the front page of Le Monde. The Mirror tabloid questioned the alliance between Prime Minister Tony Blair and Mr. Bush. “What are you doing in our name, Mr. Blair?” said a tabloid cover featuring a first-day photo.

“I think it’s a lack of visual literacy on the part of, in this case, the military,” said Fred Ritchin, a former professor of photography and imaging at New York University’s Tisch School of the Arts and dean emeritus of the International Center of Photography.

“The attempt here, from what I understand, seems to have been to try to show good guys rounding up those who might have been considered the bad guys, while thinking that they were doing it in a humane way,” he said. “Other people don’t see it that way.”

Both Mr. McCoy and Ms. Clarke said the Pentagon failed by not providing fuller explanations of what was happening in the photo.

“It was this tiny little slice of what happened down there, without seeing the whole pie,” Mr. McCoy said, like “taking a few words out of context” and creating an alternative narrative.

The photo showed a moment when the prisoners were cross-legged while on their knees “so they can’t get up quickly and run away,” said Mr. McCoy, who has seen law enforcement officers put prisoners on the ground the same way.

Hats and mittens were to protect against the cold in the cavernous cargo plane that brought them from wintry Afghanistan. Blackout goggles and ear coverings were to prevent the presumed enemy from communicating and perhaps plotting attacks. Turquoise masks were to shield against the possible spread of tuberculosis.

Without adequate explanation, Mr. McCoy said, “you just see the photo that outraged people.”

“I’m always of the opinion that people should be able to see most of what the government is doing,” he said. “The fact that I have a little slice of history, I don’t mind that. I don’t mind that I was the one inside the camp documenting it. If things got changed for the better, then that’s wonderful. I never witnessed any mistreatment.”

Mr. Rumsfeld tried to fix the damage by saying that the detainees were in transit and not kept that way. “I think that a lot of people saw that and said, ‘My goodness, they’re being forced to kneel,’ which is not true,” he said.

He declared it “probably unfortunate” that the images were released. The Pentagon stopped giving them out. By then, major news agencies had distributed them.

Petty Officer McCoy learned of the reaction to his photos and called his mother. “I told her that I caused an international incident. She said, ‘I’m so proud of you.’ She knew I was just doing my job.”

When Mr. Rumsfeld came to Guantánamo later that month, the photographer pulled the boss aside and apologized. The defense secretary dismissed the gesture, he said, remarking that the sailor was performing his duties.

Mr. McCoy left the military in 2009 with a 100 percent disability rating. After his assignment at Guantánamo, he went on a series of far-flung assignments, including in Iraq, wearing the heavy body armor of the time and carrying heavy gear. Mr. McCoy has five herniated disks in his back, bad knees, bad ankles and joint pain.

He still hoists a camera and sometimes dons a bulletproof vest in his current job. But the equipment is lighter. On the road, he stays in hotels, not at forward operating bases. His days of hurling himself off a hovering helicopter with packs on his front and back and heaving a 70-pound gear box are over. He drives a car to assignments.

He said he has taken far better photographs, many of them never released.

A favorite from that day showed a female soldier, the kneeling prisoners blurry in the background. Mr. McCoy said, as he perceived it, some of the men in custody “didn’t have a whole lot of respect for women working.”

But none have been reprinted and repurposed like that first-day image of the first prisoners at Guantánamo Bay.

This summer, while on vacation with his wife and daughters, they spotted it in a display in a defunct penitentiary in Philadelphia that once held Al Capone. “It had my name on it,” Mr. McCoy said. “I’m no longer surprised seeing it anywhere.”

Never did Mr. McCoy imagine that “20 years later I would still see those photos being used.” On that day, in that place, “I was thinking that I had an opportunity, being the only photographer in the camp.” History was happening and he had the exclusive, if only for the archives of the Department of Defense.