A year and a half after first sneaking into Syria to fight the Islamic State, Levi Shirley walked down an alley toward a former enemy stronghold in Manbij, an ancient city surrounded by rolling green hills and orchards in the northern part of the country. The lanky, six-foot-five-inch 24-year-old from Arvada was embedded with the YPG, a unit of the Kurdish militia that has welcomed about 100 volunteer American fighters since 2014.

It was July 14, 2016, and the YPG (the Kurdish abbreviation for the People’s Protection Units) had descended upon Manbij more than a month earlier. Nicknamed the “Manbij meat grinder” by some of the YPG fighters because of the brutal urban battles taking place there, and the casualties the medics were dealing with, the city was a strategic hub for the Islamic State (also known as ISIS or ISIL). From there, the group funneled weapons and foreign fighters and launched terrorist plots into Europe and Asia. The YPG, an arm of the larger Syrian Democratic Forces, or SDF—a conglomeration of Kurdish, Arab, and other militias—had surrounded the city in early June. Trapped, the Islamic State militants dug in and fought with seemingly no regard for human life—theirs or others’—using civilians as human shields and mines to booby-trap everything from gardens and teapots to candy bars and chickens.

After weeks of some of the worst fighting of the five-year Syrian civil war, which has claimed more than 470,000 civilian lives, according to the Syrian Center for Policy Research, the YPG troops were tired and hungry. Daily rations had come sporadically, and on good days they consisted of a can of imitation tuna and a stale piece of naan. So Shirley and another American YPG fighter named Porter Goodman, a 28-year-old computer science student at Brigham Young University turned combat medic with the YPG, decided to poke around the deserted Islamic State stronghold, which Shirley’s unit had cleared the night before. They were looking for intelligence and souvenirs they hoped they’d be able to trade with coalition forces in the area for food.

Although the area was rife with snipers and mines, Goodman and Shirley weren’t overly concerned about Islamic State soldiers as they walked down the alley, in part because Shirley’s unit occupied the street as well as the upper floor of the building they were about to enter. Just before they stepped into the multistory cinder-block and plaster building, the voices of several female soldiers in Shirley’s unit floated out of a window above them, reassuring them that the building was safe. Shirley walked through a doorframe—there was no door—moved down a hallway, and entered a room to his right. There he likely stepped on a pressure plate, triggering a explosion so powerful that it blew a massive hole in the wall.

Shirley, right, an Arvada native, quickly became a leader to his fellow YPG soldiers after arriving in Syria. Photograph courtesy of Uygar Onder Simsek/AFP/Getty Images

Ever since Shirley was a student at Arvada High School, he dreamed of joining the Marines. With hazel eyes and closely cropped brown hair, he was never much interested in college and dedicated his last two years of high school to joining the elite corps. He worked out with the trainees at the Marines’ Westminster recruitment office and pursued a grueling fitness routine that included daily eight-mile runs. He learned everything he could about the outfit, including its history, traditions, and drills.

Shirley’s mother, Susan, suspects her son’s fascination with the Marines was born out of a desire to win the approval of his father, Russell, from whom he became estranged after Susan and Russell separated when Shirley was 11. Russell was an Army veteran who’d done three tours in Vietnam. “Levi never said this, but to get the approval or respect of your father who was Army—what’s a step above the Army?” asks Susan, who’s 59. “In a guy’s mind, that’s the Marines or the SEALs or Special Forces.”

But Shirley failed to qualify for the Marines because of poor vision. Devastated, he began to search for other ways to fulfill his dream. Around that same time, the Islamic State had emerged as a mainstay of international news headlines with its propensity for brutal tactics, including the beheading of journalists and the slaughtering of Kurdish and Yazidi women and children. “I saw a video of them lining up kids and doing stuff I’d never seen terrorist organizations do on that kind of scale,” Shirley said in a video made by a documentary filmmaker in early 2016. “It made me angry and it shocked me and it made me feel every possible emotion that you could possibly think of when you think of a disgusting act being committed like that. And so then I thought to myself, There’s got to be something I can do to stop that.” Shirley went online to find a way to help and soon found a website called the Lions of Rojava, the YPG’s tool at the time for recruiting foreign volunteers to fight with them.

Shirley was one of about 100 Americans—and several hundred Westerners total, according to current and former YPG soldiers—who have volunteered to fight in Syria with the YPG, a force of about 35,000 men (there is a force of women fighters allied with the YPG known as the YPJ). Ranging in age from around 20 to 70, these Western vigilantes are ex-military, farmers, college students, and documentary filmmakers, all united in their desire to fight evil and make their marks on the world. “I came out here because the Islamic State has been committing atrocities against the people of the world, and especially my fellow Americans,” Shirley said. “Anything I can do to help stop them is what I’m going to do.”

The YPG is not a ragtag guerilla group. As the war with the Islamic State has escalated, YPG has proven itself to be one of the most effective forces at battling the Islamic State in Syria. Supported by air strikes from the United States, Great Britain, and France, the YPG has made impressive gains in Syria over the past two years, including a 250-mile swath of land in northern Syria, which most Kurds and Western YPG fighters simply call Rojava, a term that has also come to embody all that the Kurdish revolution stands for. There, the Kurds have established an autonomous state whose core principles include direct democracy, gender equality, sustainability, and religious freedom.

Although fighting alongside the YPG falls into a legal gray area in some Western countries, such as Australia, the U.S. government only discourages “all travel to Syria,” regardless of its purpose. That didn’t deter Shirley, who made contact with the YPG within weeks of watching the Islamic State atrocities unfold on the news in the late summer of 2014. Not long after that, he began saving money in earnest from his dishwashing job at the Braun Taphaus and Grille in Arvada to travel to the Middle East and join the YPG. In January 2015, he headed to Syria—via Seattle, Iceland, Sweden, and Turkey. He told his mother, “I want to do something noble.” Later, as they parted ways at DIA, he told her he loved her.

Jordan MacTaggart, a Castle Rock native, joined the YPG with hopes of defending the Kurdish revolutionary movement. Photograph courtesy of the MacTaggart family.

Twenty-year-old Jordan MacTaggart joined the YPG in April 2015. Like Shirley, the Castle Rock native wanted to fight the Islamic State, but he was also attracted by the Kurdish cause, at the center of which is the establishment of Rojava. “I came out here because I believe in revolution. I believe in the rights of the people, and I believe the Kurds do this well,” MacTaggart explains in a video recorded by the YPG. “I believe if I can make a difference—any difference at all, a small difference—if I can help somebody, people anywhere, I would like to.”

Some believe the volunteers are heroes; others say they’re adrenaline junkies looking for identity and meaning in their lives. “It draws a lot of really good people for a wide variety of reasons, but it also can draw thrill-seekers and war tourists,” says Goodman, the BYU student, who joined the YPG in January 2016. “For some people, the selfish reason is, ‘I wanna go be a hero, and I wanna go do this cool stuff that I can tell stories about later.’”

Unlike Shirley, MacTaggart initially had no military aspirations. A left-leaning anarchist and vegetarian, he loved punk rock and disliked authority. Six-foot-one and sinewy, with scars from years of intravenous drug use lacing up his forearms, MacTaggart wore gauges in his ears and sported a sizable mohawk as a teen. He’d had an ominous tattoo emblazoned across his knuckles in black ink: “Born Dead.”

Tough exterior aside, he was a sensitive soul who’d long had a soft spot for the disenfranchised people of the world. At age 12, he started the practice of refusing Christmas presents; that first year he asked that his family instead give money to a charity supporting orphaned children in Darfur, Sudan. “He took everyone else’s pain on him,” says his sister, Amanda. “He felt it all.” As a means to numb that searing sensitivity, his family believes, he used drugs as a teen—including marijuana, meth, and heroin—and attended several rehab centers to try to kick his addictions. After nearly dying from an overdose at age 19, he got clean and began to search for his purpose in life.

MacTaggart had long been drawn to anarchist ideology and was familiar with the Kurds’ plight and politics. “He was attuned to injustice, and it annoyed him to be a passive spectator,” says his mother, Melissa. The Islamic State atrocities in the fall of 2014, in part, galvanized him to take action, and according to his family he had soon put together a plan to join the YPG. After years of being adrift, he’d found something he felt truly passionate about. “I’ve always believed people should do something with their lives, instead of just sitting around and going to work, punching in the nine-to-five,” he said in the video. In April 2015, he quit his construction job and headed to Syria.

In the YPG, Westerners often find brotherhood, purpose, an escape. For many of these people, it’s difficult not to succumb to the hero worship that meets them in Syria, and that adulation can keep them coming back. “When you go back (to Syria), you’re going to be treated like royalty,” says River Hagg, a documentary filmmaker who became a YPG combat medic. “You’re going to be loved because of the sacrifice you’re making. You won’t be a nobody anymore; that’s attractive to a lot of my friends.”

According to the former YPG soldiers interviewed for this story, the YPG tells recruits to bring coats, thermals, boots, flashlights, and clothes and requests that they leave anything that might raise airport authorities’ suspicions, such as body armor, at home. Volunteers are typically advised to fly into Sulaymaniyah, Iraq, where they’re given directions to a safe house. From there, they are dropped off near the Syrian border and hike into the country. At this point, the recruits could be forgiven for feeling like they’re in an action-adventure film, but few volunteers are prepared for the devastation that awaits them in Syria. “If the grass could drink blood in that fucking country,” Hagg says, “the whole place would be green.”

Shirley arrived in Syria in late January 2015 and soon after took part in the Academy, the YPG’s training program for Western recruits where the aspiring warriors learn rudimentary Kurdish, gun-handling skills, and tactical training. Whereas active-duty U.S. Army soldiers undergo about four to six months of training, the Academy lasts roughly three weeks to a month. “It’s a volunteer-type militia, so all of the discipline and rigorous training you have in the U.S. military, you don’t have—which is sad because I think that’s why we suffer so many casualties,” says Daniel Kitchens, 29, a grocery store manager from Jefferson, Georgia, who joined the YPG in June 2015 and fought alongside Shirley and MacTaggart.

At the Academy, Shirley told his fellow recruits he’d been in the Marine Corps and had been discharged after a car accident—and they believed him. “He had this expert sort of air about him,” says Robert Amos, 30, who joined the YPG in January 2015 and was at the Academy with Shirley. The YPG has an armory of mostly 30- to 40-year-old refurbished Russian weapons, and while most recruits select AK-47s because it’s easier to get ammunition for them in Syria and they’re less prone to jamming, Shirley picked an M16, the Marines’ preferred weapon, and memorized its serial number, a Corps tradition. Within a couple of days, he was leading morning drills to Marine cadences.

After graduating from the Academy, Shirley officially joined the YPG on February 19, 2015. He signed a completion-of-objective form, was issued a YPG patch, and was assigned to a “tabor,” typically a 20- to 40-person unit of men and women similar to a platoon. In line with Kurdish tradition, he was given a nom de guerre, Agir Servan (“Fire Warrior”) and dispatched to the front line in northeastern Syria’s Tel Tamer. That was followed by operations at Mt. Abdulaziz and in the Kezwane Mountains. By the time he went home after his first tour, in June 2015, he’d been in about 15 firefights and had earned the respect of his peers.

As Shirley was headed home, MacTaggart was fighting in a lonesome stretch of the Syrian desert. After graduating from the Academy in May, MacTaggart was sent to the front line of Operation Tel Abyad, during which the YPG hoped to take back land from the Islamic State that would link the Kurds’ holdings in northern Syria.

Early one summer evening, as MacTaggart’s unit crossed a field in a village outside of Suluk, a small town close to the Turkish border, they came under heavy Islamic State fire. MacTaggart dropped to the ground and found cover behind a pile of rocks, but a bullet still found his right thigh. Darkness fell, and he watched as YPG vehicles raced around the battlefield, collecting wounded soldiers. In the chaos, they inadvertently drove off without MacTaggart.

Alone and bleeding, he tied a tourniquet around his leg. If he moved too much, Islamic State fighters would shoot him. If he tried to crawl back to his unit, they might mistake him for the enemy and fire at him, so he stayed where he was, unsure if he would survive the night. Around eight that evening, he made a recording on his phone of what he believed might be his last words.

“If I’m about to die, I just want to say—if this is it, I don’t regret it,” he said. “I did what I had to. I believe in this. This, don’t let it be in vain. … I go of sound mind. I go calm. I go easy. This is one moment at a time. Don’t let the revolution die.”

Jordan MacTaggart, second from the left, shown with his friends. “He was attuned to injustice, and it annoyed him to be a passive spectator,” says his mother, Melissa. Photograph courtesy of the MacTaggart family

Manbij was hot, dusty, and reeked of death. YPG soldiers say the corpses of Islamic State fighters sometimes rotted in the city’s streets. On May 31, 2016, the Syrian Democratic Forces launched the Manbij Offensive and quickly captured villages on the outskirts of town. By mid-June, the SDF began to push into the city, and the fighting intensified, as did the casualties and devastation. From June to August, more than 2,000 civilians died, along with about 600 SDF fighters, some 15 percent of the SDF force on the front line, according to one former YPG volunteer. I am seeing the belly of the devil, and I’m watching its gullet, Hagg remembers thinking after one particularly gruesome day in Manbij.

Unbeknownst to his family, whom he’d told he was headed to school in Texas, Shirley had returned to Syria in February 2016, and by early summer, he was in Manbij. Even though he’d come home from his first tour suffering from post-traumatic stress disorder, according to his mother, and assured his family that he wouldn’t return to the war, he still had a deep desire to defeat the Islamic State (which is sometimes referred to as Daesh). “People are much happier saying ‘No, no, no; let someone else go. It’s someone else’s problem,’ ” Shirley said in a video filmed last year. “Well, it’s not someone else’s problem. It’s our problem. Daesh is everybody’s problem. So if something happens to me, I can say, ‘Hey, eventually I’m going to die anyway someday; at least I died for a good cause.’ ”

Like Shirley, MacTaggart couldn’t resist the pull of Rojava. He didn’t die that night outside of Suluk, after he’d been shot in the leg. The next morning, he crawled back to friendly territory, a tale of survival that has become lore among YPG soldiers. And after returning to Colorado in September 2015, he was soon making plans to get back to the Middle East. “He was his truest self there, his happiest,” his sister, Amanda, says. “That’s what he was meant to do.” MacTaggart reunited with the YPG in January 2016. By June, after a series of battles in northern Syria, he too landed in Manbij.

The fighting in Manbij had erupted into some of the most gruesome of the Syrian civil war by midsummer. Islamic State fighters realized they were trapped in the city and began fighting desperately. YPG units would push into the city and return with roughly half their troops wounded or dead. “You had Islamic State fighters wanting to fight and die in Manbij,” Kitchens explains. “It was street to street, door to door, snipers and mines everywhere. It was hell.”

On the evening of July 13, Goodman and Hagg were dispatched from the outskirts of Manbij into the city to set up a casualty collection point where they could treat the wounded without having to wait until dark. In the previous days, they had received about five casualties a day, including a little girl who’d been injured by a mine, infants with trauma wounds, and a soldier who’d lost both legs and an arm to a land mine or a rocket-propelled grenade. When they arrived in the city, they joined up with Shirley’s unit and soon came across Shirley himself, who led the medics to the former Islamic State building his unit had cleared. The two men ended up sleeping there for part of the night.

The next morning, Hagg and Goodman had to attend to a series of casualties. While his unit enjoyed the morning off, Shirley had volunteered to provide cover for the medics, who waited for casualties in a secluded courtyard.

When there was a lull, Hagg and Goodman prepared a jalapeño-cheddar-flavored MRE—a “meal ready to eat”—and a smoothielike concoction of powdered milk and raspberry drink mix. Famished after weeks of mediocre YPG rations, Shirley devoured the MRE and wanted to know where he could get more. Goodman explained that they had informally bartered war souvenirs for food with the coalition forces in the area.

“I think I saw some stuff in there that they would want,” Shirley said, referring to the building his unit had cleared just one day earlier.

“Where’s this house?” Goodman asked.

“It’s right next door, just the ground floor of that house where you slept last night,” Shirley told the medics. His unit controlled the street, and he assured them that the building was safe, adding, “It’s just going to take a couple of minutes.” They debated the risks until Goodman finally was convinced it was safe. Hagg opted to stay back and try to get some sleep. Goodman and Shirley then hopped over the garden wall and disappeared into the belly of Manbij.

Less than five minutes later, Hagg heard an explosion. He grabbed his medic bag, ran down the alley, and came upon a scene of destruction. The explosion had cleared a hole from the building into the street. Through it, Hagg could see Shirley, motionless, facedown in the debris. A thick layer of dust covered his head. His eyes were closed, and he looked peaceful. It was clear to Hagg that he had died instantly. An IED had ripped through the midsection of his body.

Goodman was lying in the rubble, semiconscious and moaning. He was bleeding profusely from his head and had shrapnel wounds to his back and legs. Shirley’s unit commander pulled Goodman from the destruction, and Hagg began treating him. Later, as Goodman drifted in and out of consciousness, he kept asking, “Why did I come to Rojava?”

By early August 2016, the SDF controlled about 60 percent of Manbij, according to the Syrian Observatory for Human Rights. On August 3, MacTaggart and five others—the grocery store manager Kitchens; Jake Klipsch, a 35-year-old Army vet from Vincennes, Indiana; Freeman Stevenson, 23, a journalist from Saratoga Springs, Utah; a Swedish Kurd named Firaz Kardo; and a Kurdish soldier—formed a small patrol, which they named the Suffer Monkeys, within their unit. They were in the southeast section of the city when they received an assignment to take a building possibly occupied by Islamic State fighters.

That night, they overtook the building, going from room to room looking for members of the Islamic State and clearing the house of mines. MacTaggart lobbed a sabotage bomb up a stairwell, breaching three stories of doors at once. “That’s how you fucking open doors!” he yelled in Kurdish, to the amusement of his unit. After the building was secured, MacTaggart and Klipsch went onto the roof to watch the NATO airstrikes descend on the city. They hooted and pumped their fists as smart bombs exploded like fireworks in the city around them, showering the men in dust and debris.

The next day, just as the sun began to rise, the Suffer Monkeys received last-minute orders to clear a building about 500 feet from their position. They prepared for the assault—loading guns, checking gear, packing ammo—and lined up. MacTaggart and Kitchens, armed with sabotage grenades and AK-47s, led the way, followed by the Kurdish soldier and Kardo, the latter of whom had the radio and a Kalashnikov, and Klipsch with a PKM machine gun. Stevenson, carrying an RPG, was last.

“Are you ready, Inbred?!” MacTaggart shouted to Kitchens, using the Georgian’s nickname, just before he threw open the door. Hopped up on excitement and fear, they leapt outside and skimmed along the building. Once they’d gone about 30 feet, MacTaggart, Kitchens, and Kardo began to cross the road when suddenly Kardo was taken down by a remote-detonated land mine.

“Who’s up?! Who’s up?!” Klipsch shouted amidst the chaos. No one responded for a moment. Once the smoke had cleared, Stevenson saw MacTaggart across the street. MacTaggart was yelling “Covering fire!” and running back to the group when he was shot. The men pulled him to safety, and Stevenson and Kitchens administered CPR, but MacTaggart’s body was already growing cold.

Meanwhile, Klipsch went back for Kardo. “God damn it!” Stevenson shouted when it became clear that MacTaggart was dead. Shot under his right armpit, the bullet traveled through his heart and killed him almost instantly. Minutes later, they brought his body into the building where they’d slept the night before, wrapped him in a blanket, and closed his eyes.

About an hour and a half after MacTaggart died, Kardo also slipped away. Adrenaline morphed into rage, and Klipsch grabbed MacTaggart’s AK, stepped outside, and fired 30 rounds into the hot Syrian sun.

Back inside, the men gathered around MacTaggart’s and Kardo’s bodies. Stevenson pulled out his phone to play one of the Suffer Monkeys’ favorite battle anthems, Creedence Clearwater Revival’s “Fortunate Son.”

It ain’t me, it ain’t me, I ain’t no military son, son.

It ain’t me, it ain’t me, I ain’t no fortunate one, one.

On September 16,2016, Susan Shirley rests her head on her son’s coffin at Denver’s Union Station after Shirley’s and MacTaggart’s remains were returned to the United States. Photograph courtesy of Joe Amon/The Denver Post/Getty Images

Although Shirley and MacTaggart went to Syria separately, they came home together. On Friday, September 16, 2016, their bodies arrived at Denver’s Union Station on an Amtrak train. After roughly 7,000 miles, the men were finally home.

Their repatriation is largely thanks to Susan Shirley. After receiving a call on July 19 from the U.S. consulate in Turkey informing her that her son had been killed while fighting in Syria, she launched a remarkable effort to bring him home. “Levi loved his country, and I believed he really would want to be brought home,” Susan says. She was already working to get her son’s body back to the United States when MacTaggart was killed, as was another American YPG fighter, 27-year-old William Savage of Maryland, who died in Manbij on August 10, bringing the total number of international fighters killed in action with the YPG to 17 (by press time, four more had been killed). “And then there were three, and it seemed very much more worthwhile to bring home three men than one,” Susan says.

First, she reached out to the U.S. Department of State, which, she says, was mostly unable to help. Complicating the matter was the tumultuous and ever-changing situation in the Middle East, as well as the fact that the men weren’t in the U.S. armed forces. As such, no federal resources—money, helicopters, planes—could be used to repatriate them.

Next, Susan turned to the office of her congressman, Democratic U.S. Representative Ed Perlmutter, who agreed to help the families. “Though they did not fight as members of our armed forces, they are Americans, and as Americans, we have a responsibility to bring these young men home and to give the families relief and closure,” Perlmutter says.

From Manbij, the men’s bodies were transported by the YPG to a hospital in Al-Malikiya, Syria. From there, Perlmutter’s office worked with the YPG and the State Department to get the proper documentation so the bodies could be brought over the border into Sulaymaniyah and then on to Jordan and the United States. Ambulances with martyr photos on them were coordinated by the YPG and carried the men’s bodies across Syria to Iraq. As they drove across the Syrian countryside, people lined the streets holding martyr photos of the men, waving Kurdish flags, and flashing peace signs.

In Sulaymaniyah, the bodies were preserved and put into caskets and then transported by helicopter to Amman, Jordan, where they arrived in mid-September. From Amman, the bodies were flown to Chicago, where MacTaggart’s and Shirley’s remains were loaded onto a train to Denver. On September 16, after several weeks and $45,000 total, which the Kurdish government covered, MacTaggart and Shirley finally arrived in Colorado.

At Union Station, Amtrak workers unloaded the caskets from the train and set them on the platform. Reunited with her son, Susan Shirley rested her forehead against the casket and wept.

Perlmutter was on hand, and he gave the MacTaggart and Shirley families American flags, which had been flown over the U.S. Capitol in the men’s honor, folded into triangles and presented in boxes with glass fronts. “Both of these men did something very dangerous,” Perlmutter said. “Obviously not part of our military, but we honor them.”

Soon after Shirley died, his mother received a letter from the YPG. It was a tribute to Shirley’s sacrifice and legacy. “Levi was not only a fighter, providing additional force to our struggle. In fact, with his experience and knowledge he has been an example for younger fighters. While he has reached a vast amount of achievement up in our front lines, Levi has served the purpose of a very important bridge between us, the Kurds of Rojava. He crossed continents for the destiny of our people and humanity.”

Today, that letter sits in a trunk in Susan’s living room, alongside a scarf from Rojava Shirley brought back from his first tour, photos, and news clippings about her son. From time to time she pulls the letter out and reads it. She thinks about her son’s devotion—to his country, the Kurds, and Rojava—and a visceral instinct, a physical longing for her son, overcomes her. But there’s no anger at him for going to Syria—only pride. “You have to follow your own path in life. It’s not your mom’s path or your dad’s path. You go where you’re called, because it’s your life,” she says. “No, I’m not angry at Levi. I’m proud of him for doing what he obviously felt called to do.”