In the middle of the Sahara Desert of Morocco, less than 10 miles from the Algerian border and 80 miles from any sort of town, an unlikely pit crew organizes on the course of the Marathon des Sables ultramarathon.

Victoria Nicholson, a perky British expedition manager in bright pink, is the boss. Hassan, a 25-year-old Moroccan Berber from the outskirts of the desert, is her co-pilot and driver. He hangs out the side of a 4Runner with a tie-dyed scarf wrapped around his head. The pair squint against the sun at the line of runners trudging through a yellow-brown backdrop of plateaus. Heat simmers off the sand. Hassan spots them first.

“Duncan!” he yells at Nicholson, pointing ahead at two men, one with a slower, methodical gait, making their way to the checkpoint. Hassan quickly lays out his prayer rug on the sand below the backseat, where Duncan Slater, the taller of the two men, will sit as he gingerly pulls off his tan camouflage prosthetic legs. His best friend and running partner, Christopher Moore, sips water nearby. Hassan quietly teases out a mattress from the net on top of the car to make a small spot of shade.

“Cheers, mate,” Slater tells Hassan, and hoists himself back up.

Eight miles down, 44 to go.

This is the toughest day of “the toughest footrace on Earth,” and Slater is four days into his quest to become the first double amputee to complete the 153-mile, six-day ultramarathon, which requires competitors to carry all of their food and supplies throughout.

Duncan Slater, a double amputee, and other competitors cover 156 miles in six days in scorching Morocco. (Roman Sepulchre)

No one would fault Slater, 37, for giving up after Stage 1 — or, certainly, for not having tried at all. Each year, more than 1,000 runners agree to a week that will guarantee profound physical and emotional pain. On the 21.1-mile first day, almost 30 runners drop out after strong winds whip up the sands of the famous pink-orange Erg Chebbi dunes and obscure the course. Temperatures rise past 100 degrees, and the course tracks over cracked, dry lake beds, steep “jebel” climbs and sloping sand dunes.

In the months before the race, people openly doubted whether a double amputee could finish an ultramarathon in which well-trained professional athletes often fail. For Slater, the harder the challenge, the more he is reminded of what he can accomplish. He seeks out races or climates that everyone finds hard.

Being on the same level as everyone else is good for his mental state, he said. It is both grounding and rejuvenating. In facing the same pain as other athletes, he is brought back to the man he was before an improvised explosive device blew up his vehicle in Afghanistan in July 2009. In pushing through, he is reminded of how little has changed about his determination.

Slater once read a book about a free mountain climber, and one scene stuck with him.

“He was stranded on this piece of rock, and if he lets go, he’s going to drop,” Slater said. “And he just said, ‘You can only control three feet around you at any time.’

“It sounds really daft. But I kept thinking of it. I can’t control the weather. I can’t control the sand dunes. I can’t control the prosthetics. But I can control the next three feet. And that’s what I’m going to have to do. If I can take three feet off at any time, I’m chipping away.”

Duncan Slater, during the Marathon des Sables in Morocco. (Walking With The Wounded/Walking With The Wounded)
The explosion

Slater was halfway through his fifth tour with the Royal Air Force when the explosion broke the Englishman’s back and severely injured both legs. Moore was a few cars in front and helped load him onto the helicopter.

Slater was told he would never walk again and would stay in a wheelchair for the rest of his life. A year after his injury, both legs were amputated just below the knee. Within six weeks, he was walking. Within a day of walking, he was asking about running. The amputation didn’t signal a loss, but a chance to get moving again.

“It was a huge window of opportunity for me to make the most of anything and everything,” he said. “I wanted to somehow give back to everyone who helped me.”

He wanted to show his medical staff — the nurse who traveled with him from Afghanistan, the doctors who cared for him, and his wife, Kim, who was five months pregnant at the time of his injury — how he was taking advantage of their work.

That got him started, and the response from others kept him going.

“People would come up to you and say, ‘I want to do something now,’ ” he said. “It gives you a kind of buzz . . . when people say ‘If you can do that, now what can I do?’ ”

In 2013, Slater trekked to the South Pole on a 208-mile, three-week ski with a group of other injured servicemen and Prince Harry as part of the Walking with the Wounded “South Pole Challenge.” The rationale was, if he was capable, “why not go all out?” In April 2015, he ran the London Marathon with Moore, and the next day, contacted Walking With The Wounded about a spot in the 2016 Marathon des Sables.

He needed specially designed legs for the desert, and the most robust materials possible — titanium and carbon fiber — helped create a pair that would require little adjustment. Nicholson secured a spot to travel with two extra pairs of legs in the backseat of Hassan’s car. A pliable, black plastic cover was inserted into the legs to protect Slater’s stumps. His black and gray shoes were designed as shrunken-down versions of the typical running blade. His gait was tested, and he is about 60 percent less efficient than the average walker.

But there is no way to have known exactly how Slater’s stumps would react to the warmth and dryness of the Sahara. By the second day, Slater’s stumps had swollen in the heat. He took out the black plastic and began to walk with just a pair of woolen socks between his skin and the prosthetics. Nicholson compared it to “being handed a different size pair of stilettos each morning to walk across the desert.”

“Looking at Dunc, and seeing how much pain he was in, I knew that if he could finish, it would be a massive milestone,” Moore said. “A massive show of what he’s capable of doing. He’s the kind of guy who wants to prove people wrong, to prove that he can do it.”

Competitors take part in the fouth stage of the 31st edition of the Marathon des Sables between Ba Hallou and Hassi Tarfa in the southern Moroccan Sahara desert. (Jean-Philippe Ksiazek/AFP/Getty Images)
The resolve

On Day 2 (25.6 miles), for the first time, Slater and Moore talked about what happened that July 31, the day Slater got injured. Slater turned to his friend of 13 years and asked, almost flippantly, what he remembered. Moore filled in the gaps. He remembered vividly what happened after the explosion, but never felt comfortable bringing it up. Neither man knew how much the other remembered of the day that changed both their lives. The desert was as good a place as any to talk about it. That took up a fair stretch of time in the dunes, Slater said.

The pair now live about 30 minutes apart and see each other at least once a week. Moore, who is called “Paddy” by the team because of his Irish origin, is the shorter, darker counterpart to Slater’s height and fair skin. Moore is a sinewy multi-marathon finisher and RAF sergeant and, outside the desert, the quieter of the two friends. But during the race, he is often the one to speak up for the pair when he knows Slater is struggling and withdrawn.

This is far from the hardest thing they’ve dealt with together, Moore said. But for him, watching Slater in pain was much more difficult than any personal physical discomfort.

On the morning of Day 4, the 50-mile-long stage, Slater laid medical tape onto the sores where the prosthetics had rubbed his skin raw. His face and back of his hands were burnt red, and his white and gray long-sleeve shirt was now stained with sand and sweat. Underneath the shirt, Slater tucked a chain with two dog tags printed with drawings by his six-year-old daughter, Lilly, along with a ring that Kim would give him before every deployment. He would return it every time he got back to the United Kingdom. After his accident, he never gave it back.

“I just don’t want to fail,” he said, repacking his bag, lighter now that he’d consumed three days’ worth of meals he had been carrying. “Not that there’s anything wrong with failing. But I think if you can still put one foot in front of another, there’s no excuse.”

About halfway through the 50-mile stage, Slater realized that even if he could put one foot in front of another, he could not mitigate the strain on his stumps. After checkpoint one, a 30-percent slope greets the runners. Moore fit a palm beneath his friend’s feet to help create a makeshift set of stairs. By mile 15, Slater could see and feel blood inside his prosthetics. He knew then that he would not tell Moore, and he would not take his legs off until he finished the stage.

Duncan Slater, right, and his best friend and running partner, Christopher Moore, brave the brutal conditions of the Sahara Desert during the Marathon des Sables earlier this month. (Dino Bonelli)
The conclusion

It is slightly before noon, 27 hours and two marathons later, when Slater and Moore shuffle into camp to muted soft rock and cheers. Nicholson stands in the sand to greet them, wiping back tears. Hassan, who has grown quickly and fiercely proud of his job on the course, waits at the side with friends to watch them arrive. Slater immediately heads to a plastic chair under a small tent and attempts to open a water bottle with shaking hands.

Most finishers are absolutely sapped at the end of this stage. Their fatigue is palpable. They stumble across the line in tears and kneel to kiss the sand. This finish marks that the worst is behind them.

Slater’s pain is more acute. He winces as he leans over and pulls off one leg after the other. These legs will not go back on. The potential risk of infection or permanent damage is not worth it. This moment guts him, Slater said, and the rest of the Walking With The Wounded crew. Moore finished the marathon stage of the next day and the final charity stage. He got the medal he said he never wanted without Slater at his side.

“The reason I did it was to finish with him,” he said.

Three days later, the British competitors have camped out at the sprawling pool at their hotel. Slater, now rested and fed, wheels around the patio, occasionally stopped by fellow runners trying to buy him a drink.

“Next year, next year,” Slater tells people over and over. There is already talk about new prosthetics and Nicholson’s return along with a medic. If Slater returns, Moore will join his best friend for another go.

“I will come back,” Slater said. “I enjoyed the whole experience. I loved it.

“My favorite moment was just the starting line every day — knowing that I’ve got another day, and with another day, I’ve got another chance.”