<P> We are now prepared to obliterate more rapidly and completely every productive enterprise the Japanese have above ground in any city . We shall destroy their docks, their factories, and their communications . Let there be no mistake; we shall completely destroy Japan's power to make war . It was to spare the Japanese people from utter destruction that the ultimatum of July 26 was issued at Potsdam . Their leaders promptly rejected that ultimatum . If they do not now accept our terms they may expect a rain of ruin from the air, the like of which has never been seen on this earth...</P> <P> The Japanese Army and Navy had their own independent atomic - bomb programs and therefore the Japanese understood enough to know how very difficult building it would be . Therefore, many Japanese and in particular the military members of the government refused to believe the United States had built an atomic bomb, and the Japanese military ordered their own independent tests to determine the cause of Hiroshima's destruction . Admiral Soemu Toyoda, the Chief of the Naval General Staff, argued that even if the United States had made one, they could not have many more . American strategists, having anticipated a reaction like Toyoda's, planned to drop a second bomb shortly after the first, to convince the Japanese that the U.S. had a large supply . </P> <P> At 04: 00 on August 9 word reached Tokyo that the Soviet Union had broken the Neutrality Pact, declared war on Japan, subscribed to the Potsdam Declaration and launched an invasion of Manchuria . </P> <P> When the Russians invaded Manchuria, they sliced through what had once been an elite army and many Russian units only stopped when they ran out of gas . The Soviet 16th Army--100,000 strong--launched an invasion of the southern half of Sakhalin Island . Their orders were to mop up Japanese resistance there, and then--within 10 to 14 days--be prepared to invade Hokkaido, the northernmost of Japan's home islands . The Japanese force tasked with defending Hokkaido, the 5th Area Army, was under strength at two divisions and two brigades, and was in fortified positions on the east side of the island . The Soviet plan of attack called for an invasion of Hokkaido from the west . The Soviet declaration of war also changed the calculation of how much time was left for maneuver . Japanese intelligence was predicting that U.S. forces might not invade for months . Soviet forces, on the other hand, could be in Japan proper in as little as 10 days . The Soviet invasion made a decision on ending the war extremely time sensitive . </P>

Which agreement between the united states and japan first addressed the role of japan and korea