WASHINGTON » Feeling outcast and alone in Iraq, Bradley Manning, then a 22-year-old Army private, turned to the Internet for solace in early 2010, wanting to share with the world what he saw as the unconscionable horrors of war, an act that resulted in what military prosecutors called one of the greatest betrayals in the nation’s history.

Within months, he was arrested for making public, through the WikiLeaks organization, the greatest cache of sensitive government information since the Pentagon Papers. He was called a traitor by his government; confined to a tiny cell 23 hours a day at the Marine base at Quantico, Va., and the Army brig at Fort Leavenworth, Kan.; and finally court-martialed in Maryland.

As prosecutors accused Manning of being a self-promoting "anarchist" who was nothing like the tortured man of principle portrayed by his lawyers, supporters around the world celebrated him as a martyr for free speech. But the heated language on both sides tended to overshadow the human story at the center of the case.

That story involved the child of a severed home, a teen bullied for his conflicted sexuality whose father, a conservative retired soldier, and mother, a Welsh woman who never adjusted to life in Oklahoma, bounced their child back and forth between places where he never fit in.

Manning was a misfit as well in the Army, which he joined in the hope of gaining technical skills and an education, and which eventually sent him to Contingency Operating Station Hammer, a remote post east of Baghdad, where he had access to some of the nation’s deepest military and diplomatic secrets. In early 2010, he covertly downloaded gun-camera videos, battle logs and tens of thousands of State Department cables onto compact discs while lip-syncing the words to Lady Gaga songs.

He anonymously made contact with WikiLeaks to spill his secrets, hoping, as he told the military court that convicted him on Tuesday, to "spark a domestic debate on the role of the military and our foreign policy in general." Whatever his motives or inner conflicts, Manning knew he was violating the law and military regulations.

According to a new documentary about WikiLeaks and the Manning case, "We Steal Secrets," by filmmaker Alex Gibney, Manning thought that in Julian Assange, the founder of WikiLeaks, he had an ally.

"Manning invested more in that relationship," Gibney said in a telephone interview Tuesday. Seeking a more sympathetic ear, Gibney said, Manning confessed his deed, and his multiple personal torments, to Adrian Lamo, an accomplished computer hacker he had met in a chat room online. Lamo drew him out, and then turned him in to the authorities.

"He was a naive idealist. He was not a spy," said Gibney, whose film portrays Manning sympathetically. "He didn’t get any money for this. He didn’t go to a foreign government. Remember, he did plead guilty to actually leaking to WikiLeaks, but he wouldn’t plead guilty to being a spy, because he didn’t think he was one, and I don’t, either."

In his conversations with Lamo, who shared his computer chats with Wired.com, Manning said he had been ignored and isolated at work. "I just wanted to be nice, and live a normal life," Manning wrote. But he said he had seen things that troubled him that he felt helpless to do anything about.

According to the chat logs, he was first dismayed by the detention of 15 people in Iraq for printing criticism of Prime Minister Nouri al-Maliki. "After that," he wrote, "I saw things differently."

In a long statement to the military court this year, he said he was also disturbed by footage shot by an Apache helicopter of an attack on a street in Baghdad in July 2007 that killed two Reuters journalists and several other men. He called the footage one in a series of "war porn-type videos" he had seen that sickened him. The video was among the material he provided to WikiLeaks, which distributed it widely without identifying its source.

While larger questions about government secrecy and the role of the media in the Internet age swirl around his the case, the roots of Manning’s behavior may spring as much from his troubled youth as from his political views.

He spent much of his childhood alone, playing video games or huddled in front of a computer when he was living with his mother in Haverfordwest, Wales. He was teased relentlessly there for his foreign ways and began to act out in school.

After several outbursts, his mother sent him back to Oklahoma, where he worked briefly at a computer software store. But several angry clashes with his father — which some friends attributed to his father’s disapproval of his sexual identity — landed him on the streets, living in his car.

Eventually, he made his way into the Army, which seized on his computer skills and trained him as an intelligence analyst. While stationed at Fort Drum, N.Y., friends said in interviews, Manning met a student from Brandeis University named Tyler Watkins, and fell in love. Some of Watkins’ friends were part of a burgeoning hacker community at the Massachusetts Institute of Technology.

That community, friends said, embraced the young Army private: his geeky fascination with computers, his liberal political opinions and his sexual orientation.

While he seemed to thrive in that world, his military career was tarnished by violent outbursts. While serving on a base east of Baghdad, he was reprimanded twice, including once for assaulting an officer, and he complained in emails of being "regularly ignored by his superiors" unless they needed him to fetch more coffee.

Manning rebelled quietly, friends said, wearing a dog tag that said, "Humanist," and keeping a toy fairy wand on his desk. Then, surreptitiously, beginning in late 2009 or early 2010, he began downloading thousands of government documents. He considered leaking them to The , The Washington Post or Politico, but decided to contact WikiLeaks in February 2010, several months into his deployment.

In what proved a fateful mistake, Manning then turned to Lamo, who had been convicted of hacking into several large companies, including The Times.

"I can’t believe what I’m confessing to you," Manning wrote to Lamo, after explaining that he had given WikiLeaks some 260,000 diplomatic cables. He wrote that he had exploited a classified data system ripe for the plucking: "weak servers, weak logging, weak physical security, weak counterintelligence, inattentive signal analysis."

Lamo drew Manning out, asking him what kinds of scandals he thought the leaks might provoke, and for proof that Manning had done what he said. Then, saying he was "backed into a corner ethically," Lamo turned him in.

Manning has reacted stoically to the conditions of his imprisonment, much of it in solitary confinement, although others, including his legal team and Amnesty Internationally, have loudly protested his treatment. In one of his chats with Lamo, he contemplated a life behind bars, which could be especially difficult for him because of his struggles with his gender identity.

"I wouldn’t mind going to prison for the rest of my life," he wrote to Lamo, "or being executed so much, if it wasn’t for the possibility of having pictures of me plastered all over the world press as a boy."

© 2013 The New York Times Company