The start of modern UFO culture can be traced not just to the 1947 incident at Roswell, N.M., but to World War II. Nazi scientists had been researching methods of dominating the skies over Europe and, pending victory, the United States. The Treaty of Versailles, however, prevented the Germans from building traditional weaponry; they instead focused on disc- and wing-shaped flying machines. This led to great successes in stealth technology, which married lasers and mirrors to standard aeronautical principles. But WW II ended before the Nazis could deploy their breakthrough ships. And the U.S.,...