During World War II the United States and Great Britain set in motion the project known in the United States as the Manhattan Project (the British referred to it as Tube Alloys), and shortly after the end of the war in Europe a test device was ready. The work of separating the uranium isotope U-235 from ordinary uranium ore and of obtaining Nie element plutonium, which like U-235 was fissionable, from uranium, was done in the United States for safety reasons. Shortly after the explosion of the test device the project commander, Major General Leslie R. Groves, sent a report to Secretary Stimson. Read the report that General Groves sent to Secretary Stimson