Two fundamental discoveries made in the United States support military technology. Glenn Seaborg and colleagues bombard uranium in a cyclotron and produce the fissionable element plutonium, one of nine new elements heavier than uranium that Seaborg would help discover. John Dunning and co-workers show that uranium-235 is a fissionable form of uranium and develop a method to isolate this isotope. Plutonium-239 & uranium-235 become essential for the atomic bomb.
The element plutonium is produced, and uranium-235 is isolated.