The majority of the scientific and military community involved in the Manhattan Project remained true believers.

Physicist Arthur Holly Compton, the post-war chancellor of Washington University, became one of the most staunch defenders of Cold War diplomacy. In an open letter to U.S. Sen. Stuart Symington of Missouri, Compton wrote: “There are those … who believe that by arming our nation with the most effective weapons we are exciting the world toward war. My own appraisal of history is the reverse.”

Although acknowledging the dangers of nuclear fallout, Compton stood fast in his support of nuclear weapons testing. “In my judgment,” wrote Compton, “the hazard has in certain quarters been grossly exaggerated.”