Physicists tend to think along similar lines, and when research points to new possibilities, teams of scientists around the world often quickly converge on similar realizations. This was especially true of nuclear physics in the 1930s, when European and American scientists began to understand that the atom held immense stores of energy that human ingenuity could exploit. When World War II broke out, the idea of atoms as weapons spread like wildfire. Researchers in the warring nations of America, England, Russia, and Germany all understood that a bomb might be possible, and that the first country to develop one would probably win the war. The scientists realized that their counterparts in other countries also realized this, and the race to build the first bomb became more urgent.

Some Manhattan Project scientists wanted to hide these discoveries, lest other nations get wind of them and begin building super weapons. Other researchers pointed out that the scientific pathway to atomic bombs had been laid out before the war, and most physicists already were aware of the possibilities; it would only be a matter of time before they, too, made the same follow-up discoveries needed to build a bomb.