The historian carried secrets too heavy for one man to bear.

He packed his bag with his most treasured possessions before going to bed: the 1 terabyte hard drive with his evidence against the Daesh terror group, an orange notebook half-filled with notes on Ottoman history, and, a keepsake, the first book from Amazon delivered to Mosul.

He passed the night in despair, imagining all the ways he could die, and the moment he would leave his mother and his city.

He had spent nearly his entire life in this home, with his five brothers and five sisters. He woke his mother in her bedroom on the ground floor.

"I am leaving," he said. "Where?" she asked. "I am leaving," was all he could say. He couldn't endanger her by telling her anything more. In truth, since the Daesh had invaded his city, he'd lived a life about which she was totally unaware.

He felt her eyes on the back of his neck, and headed to the waiting Chevrolet. He didn't look back.

For nearly two years, he'd wandered the streets of occupied Mosul, chatting with shopkeepers and Daesh fighters, visiting friends who worked at the hospital, swapping scraps of information. He grew out his hair and his beard and wore the shortened trousers required by Daesh. He forced himself to witness the beheadings and deaths by stoning, so he could hear the killers call out the names of the condemned and their supposed crimes.

He wasn't a spy. He was an undercover historian and blogger. As Daesh turned the Iraqi city he loved into a fundamentalist bastion, he decided he would show the world how the extremists had distorted its true nature.

"I am writing this for the history, because I know this will end. People will return, life will go back to normal," is how he explained the blog that was his conduit to the citizens of Mosul and the world beyond.

He called himself Mosul Eye. He made a promise to himself in those first few days: Trust no one, document everything.

Neither family, friends nor the Daesh group could identify him. His readership grew by the thousands every month.

And now, he was running for his life. But it would mean passing through one Daesh checkpoint after another, on the odds that the extremists wouldn't stop him, wouldn't find the hard drive that contained evidence of Daesh atrocities, the names of its collaborators and fighters, and all the evidence that its bearer was the man they'd been trying to silence since they first swept in.

From the beginning, Mosul Eye wrote simultaneously as a witness and a historian. Born in the midst of the Iran-Iraq war in 1986, he had come of age during a second war, when Saddam Hussein fell and the Americans took over. At 17, he remembers going to a meeting of extremists and hearing them talk about fighting the crusaders. "I should be honest, I didn't understand."

As for the Americans, whose language he already spoke haltingly, he couldn't fathom why they would come all the way from the United States to Mosul. He thought studying history would give him the answers.

The men in black came from the north, cutting across his neighborhood in brand new trucks, the best all-terrain Toyotas money could buy. He had seen militants before in Mosul and at first figured these men would fade away like the rest. But in the midst of pitched fighting, the extremists found the time to run down about 70 assassination targets and kill them all, hanging enormous banners announcing their arrival in June 2014.

In those first few days, he wrote observations about Daesh, on his personal Facebook page - until a friend warned that he risked being killed. He returned to find his family weeping. The smell of smoke and gunfire permeated the home.

On June 18, 2014, a week after the city fell, Mosul Eye was born.

"My job as a historian requires an unbiased approach which I am going to adhere to and keep my personal opinion to myself," he wrote. "I will only communicate the facts I see."

By day, he chatted with Daesh militants and vendors, and observed. By night, he wrote in his native Arabic and fluent English on a WordPress blog and later on Facebook and Twitter.

The city turned dark, and Mosul Eye became one of the outside world's main sources of news about the Daesh militants, their atrocities and their transformation of the city into a grotesque shadow of itself.

"They were organized as a killing machine. They are thirsty (for) blood and money and women."

He drank glass after glass of tea at the hospital, talking to people who worked there. Much of the information he collected went up online. Other details he kept in his computer, for fear they would give away his identity. Someday, he told himself, he would write Mosul's history using these documents.

The most sensitive information initially came from two old friends: one a doctor and the other a high school dropout who embraced the Daesh's extreme interpretation of religion. He was a taxi driver who like many others in Mosul had been detained by a Shiite militia in 2008 and still burned with resentment. He swiftly joined an intelligence unit in Mosul, becoming "one of the monsters of Daesh" - and couldn't resist bragging about his insider knowledge.

Once he corroborated the details and masked the sources, Mosul Eye put it out for the world to see. He sometimes included photos of the fighters and commanders, complete with biographies pieced together over days of surreptitious gathering of bits and pieces of information during the course of his normal life - that of an out-of-work scholar living at home with his family.

He took on other identities as well on Facebook. Although the names were clearly fake, the characters started to take on a life of their own. One was named Mouris Milton whom he came to believe was an even better version of himself - funny, knowledgeable. Another was Ibn al-Athir al-Mawsilli, a coldly logical historian.

International media picked up on Mosul Eye from the first days, starting with an online question-and-answer with a German newspaper. The anonymous writer gave periodic written interviews in English over the years. Sometimes, journalists quoted his blog and called it an interview. In October 2016, he spoke by phone with the New Yorker for a profile but still kept his identity masked.

Intelligence agencies made contact as well and he rebuffed them each time.

"I am not a spy or a journalist," he would say. "I tell them this: If you want the information, it's published and it's public for free. Take it."

Less than a year into the Daesh rule, in March 2015, he nearly cracked. Daesh beheaded a 14-year-old in front of a crowd; 12 people were arrested for selling and smoking cigarettes, and some of them flogged publicly.

It was too much. Mosul Eye was done. He defied the dress requirements, cut his hair short, shaved his beard and pulled on a bright red crewneck sweater. He persuaded his closest friend to join him.

"I decided to die."

The sun shining, they drove to the banks of the Tigris blasting forbidden music from the car. They spread a scrap of rug over a stone outcropping and shared a carafe of tea. Mosul Eye lit a cigarette, heedless of a handful of other people picnicking nearby.

"I was so tired of worrying about myself, my family, my brothers. I am not alive to worry, but I am alive to live this life. I thought: I am done."

He planned it as a sort of last supper, a final joyful day to end all days. He assumed he would be spotted, arrested, tortured. The tea was the best he had ever tasted.

Somehow, incredibly, his crimes went unnoticed. He went home.

"At that moment I felt like I was given a new life."

He grew out his hair and beard again, put the shortened trousers back on. And, for the remainder of his time in Mosul, smoked and listened to music in his room with the curtains drawn and the lights off.

The next month, he slipped up.

His friend the ex-taxi driver told him about an airstrike that had just killed multiple high-level Daesh commanders, destroying a giant weapons cache. Elated, Mosul Eye dashed home to post it online. He hit "publish" and then, minutes later, realized his mistake. The information could have come from only one person. He trashed the post and spent a sleepless night.

"It's like a death game and one mistake could finish your life."

For a week, he went dark. Then he invited his friend to meet at a restaurant. They ate spicy chicken, an unemployed teacher and the gun-toting ex-taxi driver talking again about their city and their lives. His cover was not blown.

The historian went back online. Alongside the blog, he kept meticulous records - information too dangerous to share.

April 19, 2015: "The forensics department received the bodies of 23 Daesh militants killed in Baiji. They had no shrapnel, no bullets, no explosives and the cause of death does not seem to be explosion. It is like nothing happened to the bodies. A medical source believes they were exposed to poison gas."

July 7, 2015: "43 citizens were executed in different places, this time by gunfire, which is unusual because they were previously beheadings. A source inside said that 13 of those who were executed are fighters and they tried to flee."

He noted a flurry of security on days when the leader, Abu Bakr al-Baghdadi, seemed to be in town.

In his mind, he left Mosul a thousand times, but always found reasons to stay: his mother, his nieces and nephews, his mission.

But finally, he had to go.

"I had to run away with the proof that will protect Mosul for years to come, and to at least be loyal to the people who were killed in the city."

A smuggler, persuaded by $1,000 and the assurances of a mutual acquaintance, agreed to get him out. He was leaving the next day. Mosul Eye had no time to reflect, no time to change his mind.

He returned home and began transferring the contents of his computer to the hard drive. He pulled out the orange notebook with the hand-drawn map of Mosul on the cover and the outlines of what he hoped would one day be his doctoral dissertation. It was time to leave.

He wanted to make sure his mother would never have to watch the capture and killing of Mosul Eye.

On Dec. 15, 2015 he left Mosul, driving with the smuggler to the outskirts of Raqqa, a pickup point that alarmed him. From there he and other Iraqis and Syrians were picked up by convoy to Turkey.

In Turkey, Mosul Eye kept at it: via WhatsApp and Viber, from Facebook messages and long conversations with friends and relatives who had contacts within. From hundreds of kilometers away, his life remained consumed by events in Mosul.

By mid-2016, deaths were piling up faster than he could document. The and airstrikes were taking a bloody toll on residents. His records grew haphazard, and he turned to Twitter to document the atrocities. In February 2017, he received asylum in Europe with the aid of an organization that learned his backstory. He continued to track the airstrikes and killings.

He mapped the airstrikes as they closed in on his family, pleading with his older brother to leave his home in West Mosul. Ahmed, 36, died days later when shrapnel from a mortar strike pierced his heart, leaving behind four young children.

It was only then that Mosul Eye revealed his secret to a younger brother — who was proud to learn the anonymous historian he had been reading for so long was his brother.

With his beloved Old City destroyed, Mosul Eye launched a fundraiser to rebuild the city's libraries because the militants had burned all the books. None of his volunteers knew his identity.

From a distance, finally writing his dissertation on 19th century Mosul history in the safety of a European city, he continued to write as Mosul Eye and organize cultural events and fundraisers from afar - even after Mosul was liberated.

The double life consumed him, sapped energy he'd rather use for the doctoral dissertation and for helping Mosul rebuild. And it hurt when someone asked the young Iraqi why he didn't do more to help his people. He desperately wanted his mother to know all that he had done.

He felt barely real, with so many people knowing him by false identities: 293,000 followers on Facebook, 37,000 on WordPress and 23,400 on Twitter.

In hours of face-to-face conversations with The Associated Press over the course of two months, he agonized over when and how to end the anonymity that plagued him. He did not want to be a virtual character anymore.

On Nov. 15, 2017, Mosul Eye made his decision.

"I can't be anonymous anymore. This is to say that I defeated. You can see me now, and you can know me now."

He is 31 years old. His name is Omar Mohammed.

"I am a scholar."