In the 1970s, Messner championed the cause for ascending Mount Everest without supplementary oxygen, saying that he would do it by fair means or not at all. In 1978, he reached the summit of Everest with Habeler. This was the first time anyone had been that high without supplemental oxygen and Messner and Habeler achieved what certain doctors, specialists, and mountaineers thought impossible. He repeated the feat, without Habeler, from the Tibetan side in 1980, during the monsoon season. This was Everest's first solo summit.