On the night of May 5, 2017, Eliud Kipchoge, the world’s best marathon runner, lay awake with his eyes open and his mind racing.

Under ordinary circumstances he is amiable and serene, with his furrowed, leonine features often lit with an ice-white smile. But that night, in his room in the Hotel de la Ville in Monza, Italy, he was more nervous than at any other time in his professional life. In the morning, on the 63rd anniversary of Roger Bannister’s historic sub-four-minute mile and at the culmination of Nike’s three-year-long Breaking2 project, he would attempt to do something nobody had ever come close to doing: run a marathon in less than two hours.

Kipchoge had asked Valentijn Trouw, one of his managers, to wake him at 2:45 am, exactly three hours before the start of the race. But when Trouw checked Kipchoge’s WhatsApp profile at 2:29, he found him online and awake. The pair decided to go to breakfast. In the hotel restaurant, Kipchoge betrayed no hint of tiredness as he greeted his two Breaking2 competitors—Zersenay Tadese, the current world-record holder in the half marathon, and Lelisa Desisa, a two-time winner of the Boston Marathon, neither of whom could sleep, either—or to the 30 pacemakers who had been recruited to guide these three contenders around the course. As Kipchoge ate his oatmeal, he smiled and shook hands with the battery of scientists and designers from Nike who circled the hotel, sleepless themselves.

At 4:15, Kipchoge was driven to the Autodromo Nazionale Monza, the Formula 1 racetrack whose 1 1/2-mile junior circuit had been chosen by Nike to host the two-hour attempt. It was starless and overcast: 53 degrees Fahrenheit and a little humid. In the home straightaway, where the race would end, giant screens showed gauzy highlight reels of the athletes in training, and the tarmac was lit in lurid pinks and blues as a crowd of 800 people waited for the show to begin.

On the back straightaway, where the race would start, there were no crowds. The atmosphere was tense and quiet. After changing into a red-orange singlet and arm sleeves, black half-tights, and the controversial racing shoes that Nike had engineered for him and his competitors, Kipchoge began a 30-minute warm-up: some easy jogging followed by a few “strides”—sprints to wake up the body. He spoke very little.

Kipchoge’s anxiety came not from the mere prospect of having to race, which he always welcomes, or from the expectations of Nike, which had spent millions of dollars applying the most advanced technology and sports science to get a marathon runner across the finish line in under two hours. Kipchoge was nervous because he simply didn’t know how his body would react to the stress of running so fast for so long. The fastest anyone, ever, had run a marathon was 2:02:57. Kipchoge wanted to run nearly three minutes faster, a 2.4 percent improvement, which might sound small but represents a giant leap in human performance. And when the body fails in the marathon, it can fail dramatically and painfully. Millions of people across the world were tuning in to watch livestreams of the event. Kipchoge, the marathon’s reigning Olympic champion, faced the real prospect of not just failure but mortification.

He was also aware of the skepticism, if not venom, that many obsessive running fans felt toward the Breaking2 project. Since Nike announced its effort to break the two-hour mark last December, many have called it a barely veiled marketing exercise for the shoe behemoth and a derogation of the sport’s spirit. Some decried Breaking2’s emphasis on record-breaking in a sport recently beset by a myriad of doping scandals, particularly from East Africa. A typical post on the influential LetsRun message board read simply, “What a stupid publicity stunt. I hate Nike even more after this.” Kipchoge believed all the complaints would dissolve if he could achieve what so many had thought impossible. But first, he had to do it.

At 5:45 am, the starter’s air horn bleated and the three athletes shot off into the darkness.

A black Tesla Model S, with a digital clock mounted on its roof, was parked at the starting line in Monza. The electric car would lead the athletes around the track, driving at a constant 1:59:59 pace and showing them their split times on the display. The Tesla also shot out a green laser onto the ground, which would help the pacemakers know exactly how fast they needed to run to maintain the two-hour pace. The sight of the lead athletes warming up in their vividly colored uniforms among the black-clad pacers, and the green laser beams spilling across the tarmac, was strange and eerie—like a silent, illicit rave on a deserted freeway.