The failed military coup before Hirohito’s surrender broadcast was the Kyūjō incident.
On the night of August 14–15, 1945, Army officers opposed to surrender attempted to seize the Imperial Palace in Tokyo. Their aim was to prevent the recorded surrender address from being broadcast and to keep Japan fighting. The plotters placed the palace grounds under their control and searched for the recording containing the Emperor’s message.
The coup failed because senior commanders did not provide the support the rebels needed. The recording was hidden and preserved overnight, and the conspirators eventually withdrew. Hirohito’s address was broadcast at noon on August 15, announcing Japan’s acceptance of the Allied terms.
The incident is also called the Imperial Palace Incident. It is distinct from the February 26 Incident of 1936, another attempted military uprising in Tokyo. The Kyūjō incident demonstrates that Japan’s surrender remained politically dangerous even after the Emperor had decided to accept it.