In 1937 Bates, with Bradford Washburn, made the first ascent of Mount Lucania in Yukon, which was then the highest unclimbed mountain in North America. It was also one of the most remote and inaccessible and had been declared "virtually impregnable". The pair enlisted the aid of the pilotRobert Reeve to fly them to the mountain, but when they landed on the Walsh Glacier the aeroplane sank into the unexpectedly soft snow. After they had spent five days digging it out Reeve departed, warning Bates and Washburn that he would not be able to return to collect them as planned and that they would have to walk back to civilization. The pair climbed Mount Lucania, and the nearby Mount Steele, and were then faced with a trek through wilderness to Burwash Landing, without maps. They abandoned some of their food to save weight, expecting to restock at a cache left behind by an earlier expedition. However, the cache had been plundered by bears, and Bates and Washburn survived on mushrooms and squirrels during the trek out. Flooded rivers forced them to detour many miles out of their way, and they had eventually walked an estimated 156 miles by the time they reached Burwash Landing, 32 days after arriving on the glacier. The two men lost around twenty pounds each during the walk out.
K2
In 1937, Charles Houston invited Bates on an expedition to K2 for 1938, the world's second highest mountain. It was the first expedition to the mountain for nineteen years, and while the focus was on reconnaissance and assessing the feasibility of different routes, Bates was part of a group which reached within 800 m of the summit on the Abruzzi Spur, which would become the preferred route on the mountain. Bates and Houston returned to K2 with a new expedition in 1953. The expedition failed due to bad weather and the illness of Art Gilkey, but was widely praised for the courage shown by the team in their unsuccessful attempt to save Gilkey. During the descent, Bates and five other climbers were involved in a near-fatal fall, saved only by the strength of Pete Schoening, who was the last man on the rope. Bates later received the David A. Sowles Memorial Award for his part in the attempted rescue.
Bates was the author of several books. With Charles Houston he wrote accounts of their two K2 expeditions as Five Miles High and K2 - The Savage Mountain; the latter being regarded as a mountaineering classic. He also wrote Mystery, Beauty, and Danger, a study of mountaineering literature, and Mountain Man: The Story of Belmore Brown, the biography of an artist and explorer. His autobiography, The Love of Mountains Is Best, was published in 1994.