On September 18, 1980, at about six thirty in the evening, Senior Airman David F. Powell and Airman Jeffrey L. Plumb walked into the silo at Launch Complex 374-7, a few miles north of Damascus, Arkansas. They were planning to do a routine maintenance procedure on a Titan II missile. They’d spent countless hours underground at complexes like this one. But no matter how many times they entered the silo, the Titan II always looked impressive. It was the largest intercontinental ballistic missile ever built by the United States: 10 feet in diameter and 103 feet tall, roughly the height of a nine-story building. It had an aluminum skin with a matte finish and U.S. AIR FORCE painted in big letters down the side. The nose cone on top of the Titan II was deep black, and inside it sat a W-53 thermonuclear warhead, the most powerful weapon ever carried by an American missile. The warhead had a yield of 9 megatons—about three times the explosive force of all the bombs dropped during the Second World War, including both atomic bombs.