The first person to climb the 14 eight-thousanders was Italian climber Reinhold Messner who took 16 years between 1970 and 1986 and completed the feat without the use of supplementary oxygen.[2] By 2013, the feat had been achieved in 7 years and 310 days by South Korean climber Kim Chang, who also did not use supplementary oxygen.[3] Purja decided to use oxygen above 7,500 metres (24,600 ft) for Project Possible based on prior experiences when not using oxygen on past eight-thousander climbs would have stopped him from saving the lives of stricken climbers (something he ended up doing several times during the project).[3] In 2021, when leading a larger all-Nepali team to complete the first winter ascent of K2, Purja did not use oxygen.[4]