Acclimatization is the long-term adjustment that humans experience when exposed for weeks or months to high altitude. Acclimatization is important in this context because a warfighter who is acclimatized to high altitude is immune to high altitude illness, has superior work capacity, and has cognitive function approaching that found at sea level. In other words, the acclimatized warfighter is optimally equipped for task completion at high altitudes. Currently no drugs are known that will cause a warfighter to become acclimatized. We propose thatpre-treatment with proly hydroxylase inhibitors at low altitude will mimic acclimatization thus creating for warfighters during acute exposure to high altitude immunity to high-altitude illness, along with improved exercise and cognitive performance.