Journey inside the top-secret headquarters of NORAD–the North American Aerospace Defense Command–a binational military command composed of the United States and Canada. Established in 1958 during the height of the Cold War, NORAD’S initial mission was air defense against a bomber attack by the Soviet Union. We see how its primary mission has changed through the years, and go inside the Cheyenne Mountain Operations Center, one of history’s most ambitious underground building projects.