Air-raid sirens are so common in Zaporizhzhya Oblast, a region in southeast Ukraine over which the country and its Russian invaders are fighting, that most people don’t react to them anymore. What follows after this one isn’t the blast of a missile or the crump of an artillery shell. There is no air threat this time. Instead, there’s the distant pop of a mine somewhere to the south.

I’m 10 miles behind the front line, well within artillery range, embedded with civilian medics from the international humanitarian organization MOAS. I’m here having delivered them an ambulance. I’m not an ambulance driver as such—I’m a journalist, and I mostly write about cars. But test driving Maseratis on Riviera roads gets a little samey after a while, believe it or not. I wanted to go somewhere different, in something different, and to see this war firsthand.

The medics have turned a nearby farmhouse into a stabilization point. A call comes in to say their seventh “red” patient of the day is incoming. Shortly afterward, a khaki-colored van with a white cross on a window arrives: the Ukrainian Army is dropping off one of its own.

Losing his apartment in Hurricane Katrina gave Christopher Catrambone a taste of what it feels like to be a refugee.

The soldier is 35 years old, 300 pounds, and that mine has ripped his stomach apart. He’s stretchered into the farmhouse for anesthesia and temporary surgery before the MOAS ambulance can drive him the 30 minutes to the hospital in downtown Zaporizhzhya. Seven big fragments of mine are removed from his abdomen, and he’s patched up and put in the ambulance, the converted Toyota Land Cruiser that I’d driven 1,000 miles from the Polish border to get here.

It’s one of 50 ambulances purchased by MOAS, one with unrivaled off-road ability. If the Ghostbusters did the Dakar Rally, this is what Ecto-1 might look like. The four-by-four has had its ride height raised, and emergency lights, bull bars, a winch, chunky tires, and special shock absorbers fitted, along with a treatment bay behind the driver’s seat that’s almost tall enough to stand up in. It cost $107,500, including all the medical equipment inside, which is funded by MOAS’s private donors, the largest of whom are American.

Sometimes the journey from field hospital to proper hospital can take four hours.

We turn on the emergency blue lights and sirens for the drive to “Zap,” swerving in and out of traffic. All the major directional signs have been scratched out to confuse the enemy. The road is lined on either side by vast sunflower fields, representing the yellow in the Ukrainian flag, with the blue represented by the cloudless summer sky.

Dr. Inna Demiter, our onboard anesthesiologist, describes the patient as “difficult.” He has diabetes. His oxygen level and blood pressure are low. But Dr. Demiter is reassuringly calm. Once we get to the hospital, she signs the paperwork and hands over responsibility. “He’ll live,” she tells me on the way out. “He may even return to the battlefield in a few months.”

Sometimes the journey from field hospital to proper hospital can take four hours. Helicopters aren’t an option, as they risk being shot down. Yet MOAS has never lost a patient in its role as a transportation service. Not one.

There are three categories of casualty. Green means walking wounded. Yellow is more serious. Red implies life-threatening injuries, and MOAS has been tasked with taking care of 80 percent of Ukraine’s red front-line casualties—other groups providing medical aid, such as Médecins sans Frontières, account for the remaining 20 percent.

MOAS has never lost a single patient in its role as a transportation service.

So far, MOAS claims to have treated more than 20,000 soldiers and 20,000 civilians, and has also trained 20,000 people in the military, hospitals, and civil protection (police, fire, etc.) in combat medicine.

Anticipating the war, MOAS has been in Ukraine since a month before Vladimir Putin’s troops started firing, on February 24, 2022. The NGO was established in 2014, firstly to save migrants in the Mediterranean (MOAS stands for Migrant Offshore Aid Station). In 2017, MOAS launched in Bangladesh, where it treated more than 90,000 Rohingya fleeing genocide in Myanmar and documented war crimes. MOAS’s report was later used by the International Criminal Court.

“He’ll live,” she tells me on the way out. “He may even return to the battlefield in a few months.”

The organization was founded by the garrulous Christopher Catrambone, a maverick American millionaire turned humanitarian disrupter. The 42-year-old made his money insuring U.S. military contractors and providing emergency medical assistance in conflict zones through his company Tangiers Group.

Catrambone’s father had worked as an engineer in international oil and gas, and would bring back cassette tapes of local music from his travels—far-flung places such as Algeria—which fueled the pre-teen Catrambone’s wanderlust. His humanitarian instincts were first triggered by Hurricane Katrina, in 2005. He’s a New Orleans native and says losing his apartment and his carefree bohemian life there gave him a taste of what it feels like to be a refugee.

In 2013, Catrambone and his Italian wife, Regina (whom he met in Calabria while researching his ancestry), chartered a luxury yacht and sailed out of their home base of Valletta, Malta, toward North Africa. As they headed south, Regina spotted a beige winter jacket bobbing in the water. It had come from a sunken migrant boat upon which 368 refugees died. By the end of the cruise, Catrambone had decided to set up his own search-and-rescue operation.

Catrambone and his wife, Regina, started MOAS after a migrant boat sunk near them, killing 368 refugees.

Over the next few years, MOAS rescued and assisted 38,421 people in the central Mediterranean. The group created a model that other NGOs, coast guards, and navies have since followed, saving at least a million people in total.

“It was an awakening, seeing the desperation of people who just want what we have. That’s enough for them to risk their lives,” Catrambone tells me. “So, for me, risking a little bit of money to start a movement to save those lives was nothing.” We were sitting on a park bench in Dnipro, Ukraine’s fourth-largest city and a regular recipient of Putin’s cruise missiles.

War zones aren’t new to Catrambone. Founded in 2006, Tangiers Group has operated in Iraq and Afghanistan. But this war is different. “The injuries are unlike anything we’ve seen before,” he says. “This is a major war featuring two sides with modern weaponry. In Iraq and Afghanistan, people were being injured by mortar attacks, I.E.D. blasts, suicide bombers. They were quite targeted. Here, it’s a different enemy. Neither force is moving at the moment, they’re throwing everything they have at each other, and they have similar weaponry and similar mindsets in terms of how they fight.”

Earlier, we visited Dnipro’s top hospital together to meet the head physician and observe some of the patients. I’m informed that 90 percent of injuries treated there are caused by shrapnel. This hospital only treats “red” casualties, and since the war started, 21,000 victims have passed through its doors.

Dr. Sergii Ryzhenko told me they’ve managed to save 96 percent of those people, and credited MOAS in assisting with that. Patients remain in the I.C.U. for up to three weeks before being transferred to another hospital farther to the west to convalesce.

The hospital’s deputy head, Dr. Oleksandr Tolubaiev, took me around a ward. One young soldier, who had been brought in a week earlier, was hooked up to a dialysis machine to “help with a leg injury.” “Is his leg going to be all right?,” I asked, naïvely. Dr. Tolubaiev lifted the bedsheet to reveal that the man’s left leg had been amputated.

Catrambone, hospital deputy head Dr. Oleksandr Tolubaiev, and the author.

It’s not a job for the squeamish. Catrambone says he’s always felt “cool” about death. When he was 16, a close friend died. Such was his composure at the funeral that the funeral director asked if he’d considered a career as an undertaker.

He says of his work dealing with casualties: “Once you’ve seen a hot morgue with 100 bodies mutilated by the Taliban, and you’ve needed to identify every one of them, you lose your sense of shock,” he says. “You need that here. You can’t freak out. You need to exhibit confidence and be able to think under pressure.”

When Catrambone was 16, a close friend died. Such was his composure at the funeral that the funeral director asked if he’d considered a career as an undertaker.

The Ukraine operation was started with $1 million of Catrambone’s own money. MOAS is consuming $1.1 million a month and is funded entirely by private donors. The target by the end of this year is to have raised $20 million.

Since the war started, Catrambone has been out of Ukraine for only four weeks, and a lot of his efforts go to fundraising. “You exhaust every effort you can, both in the field and raising money. If you fail, people die.”

Yet he says he’s having fun. “Yes, we see terrible things here, but it feels good to disrupt the humanitarian industry.” MOAS spends more money than other humanitarian organizations to get the best professionals. And they are all Ukrainian—at the start, the group hired medics from the U.S., the U.K., Sweden, and South Africa, “but I needed them for six months, not six weeks,” Catrambone says. He didn’t want adrenalin-junkie war tourists or volunteers who lacked commitment.

MOAS has been tasked with taking care of 80 percent of Ukraine’s “red” front-line casualties.

“A lot of these humanitarian organizations try to do what they know, replicating it in different places without modifying the process. And it becomes ineffective and a waste of money,” he says.

Catrambone runs his NGO like a start-up and seemingly has few regrets about a life spent in conflict zones. “I don’t know how much bigger an impact you can make than keeping human beings alive at their most critical time,” he says. “It’s very fulfilling.”

Thinking back to that chartered luxury yacht, has he turned his back on the high life completely? “Big time, yeah. We have nice things, but nice things don’t give it to you.” He’s talking about that fulfillment.

I sense he’s never happier than when he’s in the field, seeing the medics that he manages preserving life. Unsurprisingly, he’s pretty discreet when it comes to naming donors. He tells me two are among the top 20 wealthiest people in the world. “But these guys’ attention gets worn out, the war drags on and it slides off the news. They start getting distracted by Trump and the next election or whatever. We know so many billionaires who wake up in the morning and take a handful of pills just to get through the day. You don’t need pills here—this is it. The buzz is doing good at mass level.”

To learn more about the work that MOAS is doing in Ukraine to save the lives of people impacted by the conflict, and to donate, visit moas.eu

Adam Hay-Nicholls is the author of the upcoming Charles Leclerc: A Biography and Smoke & Mirrors: Cars, Photography and Dreams of the Open Road