During conflicts such as WWII and the Vietnam War when nations, especially the United States, instituted a military draft, how did they determine who would be drafted and who wouldn't be? Were there medical background checks to determine if someone was physically fit before they received that fateful letter in the mail, or did a 130-pound out-of-shape college student studying biology have just as much chance of being drafted into the military as a physically-fit 6'3 person of the same age?