Drug and alcohol use have historically been common among military personnel. Soldiers have used drugs to reduce pain, lessen fatigue, increase alertness, cope with boredom, or cope with the panic that accompanies battle. During the U.S. Civil War, the medical use of opium resulted in addiction among some soldiers. In the modern U.S. military, drug use became a problem during the Vietnam War in the late 1960s and early 1970s. Approximately 20 percent of Vietnam War veterans reported having used narcotics (such as heroin and opium) on a weekly basis, and 20 percent also showed signs of being addicted. Although few personnel continued using heroin when they returned home, concerns about addiction continued. Since 1981, the military has conducted regular, random drug testing of all personnel. Illicit drug use has declined significantly since...