GAZIANTEP, Turkey—Lt. Farhan al-Jassem is not a reluctant soldier, but sadness lurked behind his smile and deep brown eyes when he talked about the last 2½ years he spent trying to fight what he considers the good fight in Syria.

On a sultry July night in a tea garden in southeastern Turkey, Jassem, 29, leaned back in his plastic chair and gulped down several bottles of water as he told the story of how he came to lead a key Syrian brigade receiving training and equipment from a U.S.-organized military coalition in the battle against ISIS. As he spoke, 54 members of the larger division his brigade belonged to were finishing their training with U.S. Special Operations soldiers at a base located roughly 200 miles to the northwest.

Jassem got his first taste of the country’s roiling civil war in early 2012, when he was conscripted into Syrian President Bashar al-Assad’s army, but he hated it and bought his way out, paying $400 for permission to visit his hometown of Manbij, 40 miles northeast of Aleppo. There he quickly joined the anti-regime Free Syrian Army, before moving to a smaller Turkmen brigade and then to the so-called 30^th Division, created by the United States and its allies as the vanguard of Washington’s effort to roll back ISIS’s territorial gains.

When he spoke to the Center for Public Integrity in July, Jassem had passed an initial round of vetting to join the training and said he expected to participate in the next class—so long as the U.S. coalition kept its promises to the first set of graduates, especially a promise to “protect us against our enemies after the program ends,” he said.

But Jassem’s fate suddenly took an uncertain turn on July 28, when he was captured by a rival anti-ISIS militia, known as the Nusra Front, which is affiliated with al-Qaida and therefore an enemy of any Syrian working with Americans. Captured alongside Jassem near the northern Syrian town of Azaz were his division’s commander, 16 graduates of the allied train-and-equip program, and two other division soldiers, according to Aziz Abu Mohammad, a 30^th Division commander based in Turkey, who was interviewed by telephone.

This capture was a cataclysmic event for the division, by all accounts, and a grave setback for the U.S. train-and-equip program, which will face steeper challenges in recruiting new fighters and maintaining their morale.

But Jassem’s story—the arc of his military service and its apparently grim end—is also a lesson for America’s deepening involvement in this complex territorial conflict. It comes with many risks, both political ones and for the fighters, personal ones, since any association with the United States or the West can carry a fatal stigma on the other side of Turkey’s border with Syria.

Fighting for his country was not always part of Jassem’s plan. He briefly studied Arabic literature at a university before dropping out to move to Greece and work there for several years. When protests against Assad began back home in Syria, he joined similar demonstrations in front of the Syrian embassy in Athens, where he began to make contacts within the nascent armed Syrian opposition.

Jassem, who has a medium build, playful grin, close-cropped black hair, and bushy black eyebrows, said he was aware of the risks of joining the U.S.-led coalition effort. Graduates of the train and equip program would be returning to Syria “with targets on their backs,” he said. Nusra and other rebel groups, they knew, targeted recipients of foreign aid not just because of their anti-Western ideology, but also because they coveted the M16s and anti-tank guided missiles that coalition forces provided fighters. Even though their handlers from the Pentagon had promised to protect the trainees, Jassem said, it was a purely verbal agreement.

But Jassem said he signed up when one of his superiors from the Turkmen brigade, Col. Nedim al-Hasan, told him last March that the coalition wanted to create a new rebel group that would unite several of the anti-ISIS brigades that had splintered off of the Free Syrian Army and scattered across eastern Syria after being forced out of their homes by ISIS. The colonel, a man he’d fought with for three years, would lead the entire division, which would eventually number more than 1,000 fighters.

The division would be composed of brigades from parts of Syria east of Aleppo, where ISIS had become a greater scourge than the Syrian regime, such as Jassem’s hometown. Most were ethnic Turkmen, but some, like Jassem, were Arab. The aim, he said, was to create a force that could funnel recruits into the train-and-equip program.

The vetting process was intensive, he said, and discomfiting for many. The reason, he was told by fellow recruits, is that candidates for training were interviewed in the second stage while attached to polygraph machines by wires wrapped around their fingers. The questions were simple—had they ever fought for Nusra, for example? But the candidates had heard that similar-looking machines were used to administer electrical shocks to prisoners at Guantánamo Bay, and so the experience was frightening. Being subjected to eye and fingerprint scans added to their fears. “They felt like laboratory rats,” said Jassem.

But the program also had its allure. Most enticing to the recruits, Jassem said, was the prospect of getting satellite phones connected to vehicles, with which they could call in airstrikes from coalition warplanes when needed. They were also promised M16 rifles, and Jassem said there “had also been talk” of anti-tank weapons and ammunition.

“The coming days will prove whether the coalition is really going to help us” defeat ISIS, Jassem said. If the coalition forces keep their promises to protect the first set of trainees, “we expect the number of people in the second training group to increase,” he added.

Jassem emphasized that the coalition’s promises only covered the 54 graduates of the train-and-equip program. But when those trainees re-entered the battlefield, he said, they would rejoin their fellow fighters from the division already fighting ISIS, including about 200 men who had applied for the train-and-equip program but had been rejected.

At the time of his abduction, Jassem was awaiting a second round of vetting to join the program, having already passed the first. He was meeting his colleagues who were heading back to Syria after visiting relatives in Turkey, but they first had to pass a Nusra checkpoint several miles south of the Turkish border. They thought they had gotten permission to do so from an Egyptian Nusra leader 10 days earlier, Abu Mohammad said.

That promise proved false. Mohammad said he heard from a friend in the town of Azaz, where the group was taken after being stopped, that they were paraded through the town with the backs of their shirts pulled over their heads as Nusra fighters shouted that they had “collaborated with the crusader coalition.”

Two days after the group’s capture, a militia group affiliated with Nusra directly attacked the 30^th Division’s headquarters, killing five other graduates of the program, according to Abu Mohammed. Coalition warplanes retaliated to both incidents by bombing the headquarters of Nusra in Azaz, he added, a claim that the Pentagon declined to confirm. Hours after the raids, he told the Center for Public Integrity through an interpreter that Nusra’s reaction will likely be to execute the detainees it already has in hand and “finish” the 30^th Division. “Especially now … their fate is sealed.”

Pentagon spokeswoman Elissa Smith contested Abu Mohammad’s claim that any graduates of the train-and-equip program were detained in Tuesday’s kidnapping but said she had no further information to provide. She acknowledged that the 30^th Division and its trainees were also attacked on Friday and said that the coalition had supported them with defensive airstrikes, but she would not confirm that it occurred in Azaz and said the attacking force was “unknown.”

U.S.  Marine Corps Brig. Gen. Kevin J. Killea, chief of staff of the U.S. combined joint task force carrying out anti-ISIS operations, told Pentagon media on Friday that he had no knowledge of any abducted or injured trainees. All anti-ISIS forces in Syria “that are credible, reliable partners,” said Killea, “will receive coalition support as is required.”

This story was published by the Center for Public Integrity, a nonprofit, nonpartisan investigative news organization in Washington.