What's It Like to Climb Everest Without Oxygen?

For most climber hoping to summit the world's highest peak, donning a tank of oxygen is simply the only way to get to the top. Without supplemental oxygen, most of the more than 4000 people who have topped out on Everest wouldn't have made it, including Edmund Hillary and Tenzing Norgay, who first climbed the mountain back in 1953. But it would be two other legendary climbers who would follow in their footsteps 25 years later who would show the mountaineering community that there was another way to scale the Big Hill, and n the process they shocked the world. 
Back in 1978 most people thought that the idea of climbing Everest without oxygen was ludicrous. In fact, there may have just been two men on the entire planet that thought it was possible. They were Reinhold Messner and Peter Habeler, who traveled to the North Side of the mountain that year to attempt the impossible. They faced a myriad of challenges along the way, including food poisoning, and winds that reached 125 mph (201 km/h), on top of the usual difficulties. And all of that came before their historic summit push without using bottled O's. 
National Geographic Adventure has shared a great story about that historic ascent, including a video of Messner recalling what it was like for them on that climb. Today, a summit without supplemental oxygen remains somewhat rare, but back in 1978 Messner and Habeler might as well have been going to the moon. But their success changed the face of modern mountaineering, to the point that there are some who now believe using oxygen on Everest takes away from the purity of the climb, and is almost a form of cheating. 
Read the story in its entirety here, and not only learn about Messner and Habeler's climb, but two other alpinists who are hoping to repeat the feat this year.