The failed Japanese military coup attempted just before the surrender broadcast was the Kyūjō incident.
The attempted coup took place during the night of August 14–15, 1945. Hardline officers sought to prevent Japan’s surrender by occupying the Imperial Palace, placing Emperor Hirohito under house arrest, and destroying the recording of his surrender message.
Major Kenji Hatanaka was the principal leader. The plotters murdered Lieutenant General Takeshi Mori, attempted to fabricate military orders, and searched for the recorded speech. They failed to win support from senior commanders, including the Eastern District Army, and could not secure the palace or stop the broadcast.
The coup collapsed before the emperor’s address was transmitted. Several leaders later committed suicide, while the surrender announcement proceeded as planned. The episode is also called the Imperial Palace incident and illustrates how strongly some military officers opposed ending the war.