With the testing of the Atomic Bomb completed in the United States, the two other bombs (Little Boy, Fat Man) had arrived on Tinian on 26 July, being delivered by the . On 24 July, a directive was sent to General Carl A. Spaatz ordering the 509th to deliver its first atomic bomb as soon as weather would permit. The Japanese cities of Hiroshima, Kokura, Niigata and Nagasaki were potential targets. President Harry S. Truman gave his final go-ahead from the Potsdam Conference on 31 July.