By the time the Trinity Test was completed at Los Alamos, the American, British, and Canadian armies had successfully launched the D-Day invasion on the beaches of Normandy, France. The tide of war had changed. Within months, the American forces had liberated Paris and pushed the German army back to its own borders. With Russian armies pushing in from the east and the Americans and British crossing the Rhine into Germany proper, the Nazi dream was all but dead. On April 30, Hitler took his own life, and seven days later Germany surrendered.

Even before the end, as the Allied armies rolled into Germany, they discovered the horror of the concentration camps where millions of Jews had been put to death. The American army also discovered scientific laboratories with documents on the German effort to develop an atomic bomb. A special...