After the second bomb (and last one they had), the Japanese had said Fruk You to the Allies? The Japanese didn't know that the US only had two ready weapons but they might have; as the Japanese were still not at war with the Soviets (through whom diplomatic channels were open to the West) the fact that the Soviets knew about the Manhattan Project they might have let the Japanese know that little snippet. It would have taken the US months to build more Atomic weapons. Would they have waited until they were ready? Or have carried-on with an assault on the Japanese Home Islands?