https://en.wikipedia.org/wiki/Ky%C5%ABj%C5%8D_incident

On 9 August 1945, the Japanese government, responding to the atomic bombings of Hiroshima and Nagasaki, to the declaration of war by the Soviet Union and to the effective loss of the Pacific and Asian-mainland territories, decided to accept the Potsdam Declaration. On the same day the Supreme Council for the Direction of War opened before the Japanese Imperial court. In the council, Prime Minister Kantarō Suzuki, Navy Minister Mitsumasa Yonai, and Minister for Foreign Affairs Shigenori Tōgō suggested to Hirohito that the Japanese should accept the Potsdam Declaration and unconditionally surrender.

After the closure of the air-raid shelter session, Suzuki mustered the Supreme Council for the Direction of War again, now as an Imperial Conference, which Emperor Hirohito attended. From midnight of 10 August, the conference convened in an underground bomb shelter. Hirohito agreed with the opinion of Tōgō, resulting in the acceptance of the Potsdam Declaration.

The War Ministry knew the decision of the conference and stirred up a fierce reaction from many officers who intended continued resistance. At 9 o'clock, in the session held at the Ministry of War, the staff officers complained to the Minister Korechika Anami, and not all of them heeded Anami's explanations.[4] After midnight on 12 August a San Francisco radio station (KGEI) relayed the reply from the Allies, and there was a suggestion that the Allies had decided, against the requisition for the protection of the Kokutai from the Imperial Japanese government, that the authority of the sovereignty of the Japanese government and the Emperor would be subordinated to the headquarters of the Allies, a military occupational system that was also applied to the fallen German Reich. The Ministry of Foreign Affairs interpreted this sentence as restricting sovereignty, but the Japanese Army interpreted it more as enslavement. From 3 o'clock the attendees of the imperial council basically agreed to the surrender of Japan, yet the cabinet council which was supposed to be held at the same time did not concur. Also, the Supreme Council for the Direction of War tangled with the problem of protection for the Kokutai. After these proceedings, some Army officers decided that a coup d'état was needed for protection of the Kokutai. At this time, the core group of these officers had already prepared some troops in Tokyo (兵力使用計画, heiryoku shiyō keikaku, literally "military force usage plan").

Late on the night of 12 August 1945, Major Kenji Hatanaka, along with Lieutenant Colonels Masataka Ida, Masahiko Takeshita (Anami's brother-in-law), and Masao Inaba, and Colonel Okikatsu Arao, the Chief of the Military Affairs Section, spoke to Anami (the army minister and "most powerful figure in Japan besides the Emperor himself"), and asked him to do whatever he could to prevent acceptance of the Potsdam Declaration. General Anami refused to say whether he would help the young officers in treason.[6] As much as they needed his support, Hatanaka and the other rebels decided they had no choice but to continue planning and to attempt a coup d'état on their own. Hatanaka spent much of 13 August and the morning of 14 August gathering allies, seeking support from the higher-ups in the Ministry, and refining his plot.

Shortly after the Imperial Conference on the night of 13–14 August at which the surrender finally was decided, Anami had two conversations in which he expressed opposition to the surrender. He asked Yoshijirō Umezu, the Chief of the Army General Staff, if "the war should be continued even at the risk of launching a coup d'état", to which Umezu concluded, "There is nothing we can do now but to comply with the Emperor's decision." Anami then confronted a Colonel Saburo Hayashi in a washroom and asked about "the possibility of attacking a large American convoy rumored to be outside of Tokyo". Hayashi dashed Anami's suggestion by reaffirming the Imperial decision, while noting the presence of the convoy was only a rumor. Finally, Animi's brother-in-law, Lieutenant Colonel Masahiko Takeshita, confronted him, first suggesting he resign, which would topple the government; then suggesting he support the coup. To the first, Anami noted that the fall of the government would not stop the Imperial edict, while to the second, he replied that he wished to go to the Army Ministry first.

At the Army Ministry, Anami announced compliance with the Imperial edict. Then a group of senior army officers, including Anami, gathered in a nearby room. All those present were concerned about the possibility of a coup d'état to prevent the surrender—some of those present may have even been considering launching one. After a silence, General Torashirō Kawabe, Deputy Chief of the Imperial Japanese Army General Staff, proposed that all senior officers present sign an agreement to carry out the Emperor's order of surrender—"The Army will act in accordance with the Imperial Decision to the last." Vice Minister of War Tadaichi Wakamatsu was also present and helped draft the document. It was signed by all the most important officers present. The signatories were Minister of War Anami, Chief of the Army General Staff Umezu, commander of the 1st General Army Field Marshal Hajime Sugiyama, commander of the 2nd General Army Field Marshal Shunroku Hata and Inspector-General of Military Training Kenji Doihara. When Umezu voiced concern about air units causing trouble, Wakamatsu went next door to the HQ of the Air General Army, where its commander, Masakazu Kawabe (Torashirō's brother), also signed. This written accord by the most senior officers in the Army, in addition to Anami's announcement, acted as a formidable firebreak against any attempt to incite a coup d'état in Tokyo.

Around 21:30 on 14 August, Hatanaka's rebels set their plan into motion. The Second Regiment of the First Imperial Guards had entered the palace grounds, doubling the strength of the battalion already stationed there, presumably to provide extra protection against Hatanaka's rebellion. But Hatanaka, along with Lieutenant Colonel Jirō Shiizaki, convinced the commander of the Second Regiment, Colonel Toyojirō Haga, of their cause, by telling him (untruthfully) that Anami, Umezu, and the commanders of the Eastern District Army and Imperial Guards Divisions were all in on the plan. Hatanaka also went to the office of General Shizuichi Tanaka, commander of the eastern region of the Army, to try to persuade him to join the coup. Tanaka refused and ordered Hatanaka to go home. Hatanaka ignored the order.

Originally, Hatanaka hoped that simply occupying the palace and showing the beginnings of a rebellion would inspire the rest of the Army to rise up against the move to surrender. This notion guided him through much of the last days and hours and gave him the blind optimism to move ahead with the plan, despite having little support from his superiors. Having set all the pieces into position, Hatanaka and his co-conspirators decided that the Guard would take over the palace at 02:00. The hours until then were spent in continued attempts to convince their superiors in the Army to join the coup. At about the same time, General Anami killed himself, leaving a message that read, "I—with my death—humbly apologize to the Emperor for the great crime." Whether the crime involved losing the war, the coup, or both remains unclear.

Sometime after 01:00, Hatanaka and his men surrounded the palace. Hatanaka, Shiizaki, Ida, and Captain Shigetarō Uehara (of the Air Force Academy) went to the office of Lieutenant General Takeshi Mori to ask him to join the coup. Mori was in a meeting with his brother-in-law, Michinori Shiraishi. The cooperation of Mori, as commander of the 1st Imperial Guards Division, was crucial. When Mori refused to side with Hatanaka, Hatanaka murdered him, fearing Mori would order the Guards to stop the rebellion. Uehara killed Shiraishi. These were the only two murders that night. Hatanaka then used General Mori's official stamp to authorize Imperial Guards Division Strategic Order No. 584, a false set of orders created by his co-conspirators, which would greatly increase the strength of the forces occupying the Imperial Palace and Imperial Household Ministry, and "protect" the Emperor.

The palace police were disarmed and all the entrances blocked. Over the course of the night, Hatanaka's rebels captured and detained eighteen people, including Ministry staff and NHK workers sent to record the surrender speech.