Nearly everyone who’s seen it and lived to tell the tale describes it the same way: a horrifying, otherworldly thing of ghastly beauty that has haunted their life ever since. Many tales of the atomic bomb, however, weren’t told at all. In addition to the hundreds of thousands of Japanese civilians who died in Hiroshima and Nagasaki, an estimated 400,000 American soldiers and sailors also observed nuclear explosions—many just a mile or two from ground zero. From 1946 to 1992, the U.S. government conducted more than 1,000 nuclear tests, during which unwitting troops were exposed to vast amounts of ionizing radiation. For protection, they wore utility jackets, helmets, and gas masks. They were told to cover their face with their arms.