The use of amphetamines (also called "speed" and "uppers") by combat troops and pilots began soon after amphetamines became available. Amphetamines were put on the market in the 1930s, and when World War II rolled around, they were a favorite (although often unauthorized) method for infantry, sailors and pilots to keep alert after too many hours, or days, without sleep. World War II saw the widespread use of "24 hour combat" and long range aircraft for the first time. For the infantryman, or vehicle driver, lack of sleep became a life-threatening condition. Thousands of American troops died during the war when they fell asleep at the wheel and crashed their trucks or armored vehicles. Pilots of heavy bombers, patrol aircraft, and transports suddenly found themselves on long flights (ten hours or more) and expected to execute tricky landing procedures at the end of the mission. Infantry and sailors were called on to be "on alert" (manning their weapons) for 12-24 hours (or more) at a time with no rest. The USAF finally recognized the need for amphetamines in the 1950s, as they introduced bombers that could stay in the air for 24 hours or more (with in-flight refueling) and officially approved the use of prescription amphetamines in 1960. In the 1960s it became popular for long haul truckers, and college students cramming for exams, to use illegal amphetamines. And they were illegal (available only by prescription) for good reason. For while amphetamines kept you "up," when you stopped taking them, you risked mental depression ("crashing"), erratic behavior or worse. The drug had to be used with care. The military has long considered amphetamines just another dangerous tool they have to use to stay alive in combat. And that's basically what amphetamines are to the troops, a dangerous item that is less dangerous than the alternative (crashing while landing your aircraft, or getting jumped by an attacking enemy.)