At the beginning of June 2015, his one-year tour of duty with ISIS drawing to a close, Wakaz reappraised his life. Since completing his training at the ISIS compound near Mosul the previous summer, he had spent some six months back in his hometown, Dawr — his main duty there, he said, was manning an ISIS checkpoint — before being sent to fight a resurgent Iraqi Army at the oil-refinery complex in Baiji. With that battle still raging, Wakaz certainly had the option of reupping with ISIS, but he decided instead to return to the civilian world.

Part of his reason may have involved economics; with ISIS’ salad days clearly over, Wakaz’s pay packet often arrived late. But it most likely was rooted even more in self-preservation. Because, slowly but surely, the tide appeared to be turning against ISIS.

This was made evident to Wakaz as he contemplated just where he might go to start over. In April, the Iraqi Army, supported by American airstrikes, had recaptured Tikrit, and by that June they were closing ever tighter around Baiji. That still left Mosul and the ISIS-controlled towns in Anbar Province, but life in any of those places for an ex-ISIS militant was sure to be grim: He would be resented by his former comrades, and a dead man should the Iraqi Army take control.

Wakaz finally settled on a very different destination: the Kurdish-controlled Iraqi city of Kirkuk.

Just as in Mosul and Baiji and Tikrit, the Iraqi Army garrisoned in Kirkuk broke and fled before the ISIS offensive a year earlier. But there the similarities ended. Racing to fill the void left by the Iraqis, thousands of pesh merga soldiers had poured into Kirkuk just ahead of ISIS and managed to throw back their advance. Ever since, Kirkuk has effectively been under Kurdish control, but the melting-pot city was also teeming with both Sunni and Shiite refugees, making it a natural hide-out for both active and former Islamist militants. Although Kirkuk was a mere 60 miles from Baiji, the two cities were now separated by the heavily fortified line of the pesh merga army. It meant that, to reach his sanctuary city, Wakaz would have to travel the ISIS “ratline.”

In the same month that Wakaz decided to leave ISIS, Majd finally obtained his bachelor’s degree in hotel management from Al-Baath University. The achievement was a mixed blessing: Now he was eligible for conscription. Before the war, a male student normally received his call-up letter four or five months after graduation, but by 2015 the Syrian Army was so depleted from defections and battlefield casualties that the call-up time had shortened to a month or two, or even just a few weeks, and there was no longer any gaming the system. When the call-up notice went out, the army might simply come to your house and haul you away. “So that was it,” Majd said. “I knew that in a very short time, the army would come for me.”

Just days after his graduation, Majd’s parents handed their son $3,000 — all the savings they had left — and told him to leave the country.

“To them it was no longer about patriotism or defending the country,” he said, “but about my staying alive.” He gave a faint smile. “Plus, I would have made a terrible soldier.”

On June 21, Majd’s father escorted him to Damascus, where two days later he caught a flight for Turkey. Besides the $3,000, all Majd carried was whatever could fit into his small knapsack.

Hoping to stay at least somewhat near home, Majd began looking for work in Turkey. When that proved futile, he saw no choice but to join the migrant trail being negotiated by hundreds of thousands of his countrymen that summer, and so he headed west for Turkey’s Aegean coast, where he might seek passage to Europe. Along the way, he serendipitously met up with an old friend from Homs whom he hadn’t seen in years, Amjad, who was traveling with Ammar, another refugee from Homs. The three became a traveling team. Consequently, they shared the same overcrowded inflatable raft that, on the night of July 27, made the passage from a smuggler’s beach near Bodrum, a Turkish resort town, to Kos, a Greek island several miles away.

There, Majd and his two friends endured an agonizing wait. With Kos overwhelmed by tens of thousands of would-be migrants, Greek authorities were taking up to 10 days simply to issue the registry papers that would allow their onward travel. That summer, the migrant route through Eastern Europe was becoming increasingly inhospitable, with several governments threatening to shut it down completely. Finally, Majd and his friends received their papers late on the afternoon of Aug. 4. That left them just enough time to catch the nightly ferry for the Greek mainland, the beginning of their search for refuge somewhere in Europe.

On June 18, 2015, the first day of Ramadan, Wakaz bid farewell to his ISIS comrades and set off on the ISIS ratline for his return to civilian life. To reach Kirkuk, just 60 miles northeast of Baiji, Wakaz first had to travel west across ISIS-controlled Iraq and Syria, then north into Turkey, before slipping back across into Kurdish-­controlled territory in Iraq — an almost complete circle of more than 500 miles. The biggest potential obstacle on this well-known route was the heavily militarized Turkish frontier.

Ever since ISIS gained strength in eastern Syria in early 2014, there have been accusations that their success relied on Turkey’s keeping its border deliberately porous so that Islamist militants from around the world might pass back and forth. That charge was made most explicitly by the Russian government in late 2015. While the Turkish administration of President Recep Tayyip Erdogan vehemently denied the charge, evidence supports the Russian account. Eleven of nearly two dozen captured ISIS militants that I interviewed for this report claimed to have transited through Turkey at some point during their ISIS service. Nearly all of those 11 told me they encountered Turkish soldiers or police while crossing the Turkish-Syrian frontier and were simply waved through. That was certainly the experience of Wakaz.

“The man who was leading us, he went up to the Turkish checkpoint and talked to the guards for a few minutes,” Wakaz said. “Maybe he gave them some money, I don’t know, but then we just passed on.”

As to whether there was any chance the Turkish border guards didn’t grasp the affiliation of those they were letting through, Wakaz briskly shook his head. “Of course they knew. We were all young guys, and the man taking us across was ISIS. He went across there all the time. They knew.”

From Turkey, Wakaz made another clandestine crossing into K.R.G. territory, and by the beginning of July 2015, two weeks after he left ISIS, he was in Kirkuk and ready for a fresh start. He was soon joined there by another ISIS retiree, his brother Mohammed.

At least initially, it seemed the Hassan brothers had chosen well. In Kirkuk, they moved into a small apartment in a neighborhood favored by other ex-ISIS militants trying to escape notice, and within a week, both brothers found work on a nearby construction site. At that point, if Wakaz had a dream for the future, it was simply to lie low in Kirkuk, save as much money as possible, return home when the situation permitted and open his own small shop.

As modest and heavily conditional as that dream was, it ended on the afternoon of Sept. 7, 2015, when a black car pulled alongside Wakaz on a Kirkuk street. Rolling down his window, the man in the front passenger seat, an undercover policeman, asked the young man with the piercing eyes for his identification card.

On the afternoon of Nov. 23, 2015, I visited Majd Ibrahim at his attic apartment on the outskirts of Dresden. Provided by the local social-welfare agency, the apartment was shared by Majd and his friend from Homs, Amjad, along with six other asylum seekers, as they waited for their petitions for resident status to wend their way through the German legal system. Meals had become a new preoccupation, and two of the roommates, from India, had installed themselves as lords of the kitchen. “Their food is much better than ours,” Majd explained. “They give us a list of what to buy, and we go to the market for them, but they do almost all of the cooking.”

From Greece, the Syrian friends had traveled the migrant trail through Eastern Europe and reached southern Germany by mid-August. Majd had intended to continue on alone to Sweden, where he’d heard winning asylum was easiest, but those plans were dashed when the friends were pulled off a northbound train by the police. After being shunted between migrant holding facilities, they were taken to Dresden in mid-September.

For refugees from Homs to find themselves in Dresden held a certain paradox. The city, known for having been largely destroyed by Allied bombing in World War II, was also the center of the growing anti-immigration movement that had spread across Germany over the previous year. Right-wing nationalists were staging mass demonstrations in the city every Monday night. When I visited Majd, it had been just a week since terrorist attacks in Paris killed 130, and anger against migrants — and especially any from Muslim countries — was reaching a fever pitch.

“There have been quite a few incidents here just this past week,” Majd told me. “A lot of the guys won’t go to the city center at all right now.”

Certainly they wouldn’t be heading downtown that evening, a Monday, when the anti-immigrant speeches in Dresden’s Theaterplatz would kick off promptly at 7.

Majd spoke frequently of his intention to return to Syria; an intention that partly explained why he asked for his face not to be shown in his portrait. That afternoon I asked if he could foresee a time when such a return would be possible. He thought for a long time. “Minimum, 10 years from now,” he said. “We have a saying in Syria: ‘Blood brings blood.’ Now everyone will want to take revenge for what has been done to them these past years, so it will just go on and on. Blood brings blood. I don’t think it will end until everyone who has taken up a gun in this war is dead. Even if the killing speeds up, that will still take at least 10 years.”

By coincidence, I was with Majd the following day, when, returning to his communal apartment, he found a letter awaiting him. It was from the Federal Office for Migration and Refugees, and it informed Majd that a background check had been completed and that no problems were found; it was the last major hurdle in his petition for residency, making it all but certain that he would now be allowed to stay in Germany for the next three years. Setting the letter aside, Majd crossed to one of the attic’s dormer windows and sat, staring out at the street, for a long time.

By the end of 2015, Khulood had come up with a desperate plan. Her years of petitioning for resettlement having gone nowhere, she now saw absolutely no future for her family in Jordan. All that summer and autumn, she followed the story of the hundreds of thousands of prospective migrants making for Europe from Turkey — and, far more perilously, from Libya — aboard flimsy inflatable rafts. By December, however, it was a rapidly changing story; more and more restrictions were being placed on the migrants by European governments and, with winter coming on, the sea passage was becoming increasingly risky. As Khulood explained to her father and sisters, if ever they were to change their situation, they had to act immediately.

With Ali al-Zaidi’s health too precarious to withstand the rigors of a hard journey, it was decided that Sahar would remain with him in Amman while Khulood and Teamim made for Europe. On Dec. 4, they took a flight to Istanbul and from there followed the by-now well-worn migrant trail down the Turkish coast to Izmir. After arranging to pay a smuggler 2,000 euros for spots aboard a boat, the sisters waited. The summons finally came on the night of Dec. 11.

They were driven an hour and a half down the coast. Slipping to the shoreline in the darkness, Khulood and Teamim clambered aboard a severely overloaded rubber raft — Khulood counted at least 30 other passengers, rather than the eight or 10 it was designed to hold — which then pushed off for the Greek island of Samos, a three-hour journey.

The overburdened raft lay so low in the water that twice the outboard motor died when waves broke over it. But the greatest danger came when they nearly reached safety. On the murky sliver-moon night, the pilot misgauged his approach to the Samos beach and smashed the raft against a rock outcropping; instantly, one of the air-filled pontoons began to collapse. Ready to join the other passengers tumbling into the water from the sinking boat — fortunately, all wore life preservers — Khulood thought to glance over at Teamim. Her oldest sister sat stock-still, too paralyzed with fear to react.

“I yelled at her to jump,” Khulood recalled, “because the waves were very high and they were going to smash us against the rocks, but she just couldn’t move. I saw that she was going to die, but I thought, We’ve come too far together, we must now share our fate.”

Clambering over to her sister, Khulood grabbed Teamim and somehow managed to get them both clear of the sinking vessel and onto the rocks. There they were promptly knocked down by another wave, with Teamim badly hurting her leg in the fall, but at least they were now on land. In the dark, Khulood helped her limping sister up the hillside to join the rest of the migrants as they set out in search of shelter.

The following two weeks became a blur of travel and waiting and tension for the two sisters from Iraq, an object lesson in both the callous indifference of officialdom and in the life-altering kindness of strangers. After registering with Greek authorities in Samos, the sisters were allowed to board a ferryboat for the Greek mainland and Athens, where they were sheltered by a friend of a friend. With the situation at the Eastern European frontiers changing constantly — and not in any way that augured well for the thousands of migrants still streaming north — the sisters quickly moved on. By Dec. 22, through a combination of bus, train and foot travel, Khulood and Teamim had crossed five European borders to finally reach southern Germany.

There, their luck appeared to run out. Arrested shortly after crossing the German frontier, the sisters were held in jail until dark, then sent back into Austria and instructed to make for a refugee holding center in Klagenfurt. That camp was overflowing, however, and they were denied entry. With nowhere else to go, Khulood and Teamim simply huddled together outside the camp’s gates — and then it began to snow.

Their salvation was arranged through social media. After Khulood posted notice of her situation on Facebook, a small international band of activists mobilized in search of someone in the Klagenfurt area who might help the sisters. That aid soon arrived in the form of a local Green member of Parliament, who took Khulood and Teamim to a cafe to eat and warm up. At the cafe, the politician also sent out an urgent message seeking a local family who might temporarily take in the sisters; within an hour, he had received eight offers. From the cafe, the Zaidi sisters were taken to the home of Elisabeth and Erich Edelsbrunner.

“Today is the first day we feel comfortable and relaxed,” Khulood emailed a friend in England the following day, Christmas Eve. “The family is very nice. They have given us our own room. They have a very lovely dog. I love him.”

In December 2015, Wakaz Hassan was being held on suspicion of terrorism in a small former police station at the edge of a village about 10 miles from Kirkuk. Along with approximately 40 other suspected terrorists, Wakaz, now 21, spent almost all his waking hours kneeling in a small and fetid room of the secret prison run by the K.R.G.’s security service, Asayish. On those rare occasions when he was taken from the communal room, he was handcuffed and blindfolded. Three months after being picked up on the streets of Kirkuk, he still had no idea where he was.

After his arrest, Wakaz quickly confessed to having been an ISIS militant. He provided details of his service, including the six executions he carried out in Mosul. Whether this confession was coerced through torture was impossible to know — in conversation with me in the prison, Wakaz insisted that the Asayish interrogators hadn’t mistreated him in any way, but even tortured prisoners tend to say that when their captors are standing over them. Over the course of our two long interviews, the young man sometimes contradicted himself, perhaps a result of trying to gauge what his questioner and captors might want to hear. That said, there seemed a core candor to his words that perhaps was at least partly because of a stricken conscience.

“I did bad things,” he told me, “and I need to confess to them before God.”

Shortly after his arrest, Wakaz also informed on his brother Mohammed. It took Asayish a month to track down the older Hassan sibling, and he was being held in a different prison near Kirkuk. There had been no contact between the brothers since their arrests, but Wakaz hoped Mohammed was also making a clean slate of things. His main goal now, he said, was to atone for his crimes by helping the authorities identify whichever of his former ISIS colleagues were still alive. “If I had a chance to do it over again,” he said, “I never would have joined ISIS. I saw the evil things they did, and I know now that they aren’t true Muslims.”

Despite this professed change of heart, the 21-year-old is cleareyed about his future. “I have no illusions, and I have no hope,” he told me. “I believe I will spend the rest of my life in prison.”

But Wakaz was basing that belief on the fact that he had been captured by K.R.G. investigators and remained in Kurdish custody. In reality, a grimmer future was being planned for Wakaz, one plainly laid out to me by a senior Asayish officer at the secret prison.

Since the events of June 2014 — when the Iraqi Army in Kirkuk melted away before the ISIS assault, and the Kurds rushed unto the breach — the city has technically been under the joint control of the Iraqis and the Kurds. But this collaboration exists largely on paper. In practice, the Kurdish authorities have little faith in their Iraqi counterparts and see even less reason to cooperate with them on security matters. Nowhere is this separation more evident than on issues relating to ISIS.

“That’s why we haven’t told the Iraqis about the guys in here,” explained the Asayish official. “If we did, they would demand we hand them over, since most of their crimes were committed on Iraqi territory. Then they would either kill these guys outright or, if some of them are high enough up in the ISIS leadership to arrange a bribe, let them go. We just can’t trust the Iraqis at all.” In light of that, the Asayish plan is to keep Wakaz under wraps and to use him to identify other ISIS militants they capture and with whom he might have served in the field. Once his usefulness to Asayish comes to an end — and that may not be until after the retaking of Mosul and the trove of ISIS militants expected to surrender there — Wakaz will be handed over to the Iraqi authorities. At that point, his future will be short and preordained.

“He thinks his life will be saved because we have him, and he knows we don’t execute,” the Asayish officer said. “But Iraq does. The Iraqis will try him in their courts, and they will give him a death sentence. Then they will transfer him to a prison in Iraq to be hanged.”

When I asked if there was any chance that, because of Wakaz’s assistance in unmasking other ISIS militants, a judge might show leniency in his case, the Asayish officer quickly shook his head. Or that he could somehow cut a deal to spare his life? The officer pondered briefly, then shook his head even more forcefully.

“If he was senior ISIS, maybe,” he said. “But he is a nobody and poor. So no. No chance.”

The New York Times Magazine