Tu Youyou, a researcher at the China Academy of Traditional Chinese Medicine in Beijing, joins in 1969 the classified "Project 523", a military initiative ordered directly by Mao Zedong to find an effective treatment against drug-resistant malaria, which was severely affecting Chinese troops fighting in the Vietnam War. Tu leads a systematic review of more than two thousand classical texts of traditional Chinese medicine in search of historical remedies against malaria-like fevers, eventually identifying a reference to the plant Artemisia annua (sweet wormwood) in a 4th-century Chinese medical text. The initial extracts obtained using traditional extraction methods — using heat — prove ineffective in animal trials; Tu reasons that heat might be destroying the active compound, and develops in 1972 a low-temperature extraction method using ethyl ether that successfully isolates artemisinin, a compound demonstrating one hundred percent efficacy against the malaria parasite in animal models. Tu personally undergoes, as the first volunteer, the compound's safety trials before beginning clinical trials in human patients. Artemisinin and its derivatives become, combined with other drugs in what are called artemisinin-based combination therapies (ACT), the first-line treatment recommended by the World Health Organization against malaria, saving, according to WHO estimates, millions of lives in the decades following its clinical introduction.