Allied bombers had been used on August 13, 1945 dropping leaflets over Japan which described, in Japanese, the surrender offer and the Allied response. On August 14, 1945 Hirohito met with his military leaders, several of whom spoke in favor of continuing the War. Hirohito urged them to help him bring the War to an end. Meeting then with the Supreme Council for the Direction of the War and heard out those who recommended a rejection of the Allied offer unless there was a guarantee that the Emperor would continue to reign. Hirohito then spoke:
I have listened carefully to each of the arguments presented in opposition to the view that Japan should accept the Allied reply as it stands and without further clarification or modification, but my own thoughts have not undergone any change. … In order that the people may know my decision, I request you to prepare at once an imperial rescript so that I may broadcast to the nation. Finally, I call upon each and every one of you to exert himself to the utmost so that we may meet the trying days which lie ahead.
In normal times in Japan that would have been that. It was quite rare for the Emperor to so overtly intervene in a decision of the government, indeed it was forbidden under the then current Japanese constitution, but when he did, it would have literally been unthinkable for any Japanese not to instantly obey. However, these were far from normal times.
The rest of the day was taken up with Hirohito preparing an address to his people and having a recording played to be broadcast on August 15, 1945. Washington was advised that Japan had surrendered via the Japanese embassies in Switzerland and Sweden and the Allied world went wild with joy.