The second atomic bomb was originally scheduled to be dropped on Kokura on August 11th. However, weather forecasts suggested a five-day period of cloud cover would begin on August 10th, so the day of attack was moved up to August 9th.

During the period from August 6th through August 9th, Japanese command did not respond to the Potsdam Declaration demanding unconditional surrender and were considering surrendering with the conditions that (1) the Imperial rule be preserved; (2) Japanese Imperial Headquarters be responsible for diasarmament and demobilization; (3) there be no Allied occupation; and (4) punishment of war criminals be delegated to Japanese authorities, which is really no surrender at all, merely an armistice, which the Allies had previously concluded, on the basis of the dubious peace of World War I and the nature of the Japanese war-machine, was unacceptable.

US Military Command felt, due to the general crudeness and apparent ineffectiveness of the bomb dropped on Hiroshima, that it was neccesary to bring the Soviets into the Pacific War, and persuaded Stalin to declare the Soviet-Japanese neutrality pact to be null and void and begin attacking the Empire of Japan from the North, foreshadowing a two-pronged invasion. The Soviets invaded Machuria, Sakhalin, the Kuril Islands, and North Korea on August 9th, ten hours before the the bomb was dropped on Nagasaki, with the support of US-led forces.

After Nagasaki, US forces planned for more atomic bombings of Japan and began to doubt whether “Fat Man” and “Little Boy” had created a strong enough psychological effect to compel Japanese surrender.

Due to the fact that the next bomb wouldn`t be ready until the third week of August, with six more to follow in September and October, the strategic plan for use of the bombs was reconsidered.

Allied forces wondered whether the bombs would be better used in conjuntion with a mainland invasion, less psychologically and more practically. Meanwhile, Japanese military command prepared for a Soviet invasion of Hokkaido and a US invasion of Kyushu by mobilizing troops and planning to impose martial law on Japanese civilians.

There was no indication that Japanese command was even considering unconditional surrender as a result of the bombs: troops were preparing for a two-front war, the Potsdam Declaration was ignored, and martial law was being imposed.

Japanese civilians expected the same treatment by occupied forces as they gave the Chinese and it was generally believed, due to imperial propaganda, that Americans were cannibals and would eat Japanese civilians. And while there were many atrocities committed by occupying forces after the war, including thousands of rapes, child rape, etc., the degree was no where near what had occured during the Japanese Imperial occupation of China.

In his famous radio address to the Japanese nation announcing surrender, Emperor Hirohito suggested that the new bombs had the capacity to destroy all civilization, but in his address to military command, he did not mention the bombs, but rather suggested that the Japanese military did not have the capacity to fight a two-front war against the US and the Soviets. This begs the question of whether or not the impact of the bombs was what actually compelled Japanese surrender, or whether the Soviet presence to the north was the ultimate reason.

Hirohito surrendered to the Allies on the condition that the Imperial Rule be preserved. Even this was not the unconditional surrender the Allies had demanded, but was accepted. Effectively, the Japanese had managed to negotiate an armistice, not a full surrender, despite being hit by two atomic bombs.

Soviet forces continued to attack Japanese territory after the armistice had been negotiated, which compelled President Truman to demand a full US-led occupation of the Japanese mainland and South Korea, using the bomb as leverage, having the bomb be declared the official reason for surrender. However, it is doubtful that the atomic bombings were the real reason for surrender. They were merely the official reason given.