The failed military coup attempt before Hirohito’s surrender broadcast was the Kyūjō incident.
The attempted coup began on the night of 14 August 1945, when officers opposed to surrender tried to prevent the emperor’s recorded address from being broadcast. The plotters sought to occupy the Imperial Palace, isolate Hirohito, and find the recording of the Imperial Rescript on the Termination of the War.
They received support from some palace guards and controlled parts of the palace complex, but they failed to secure the emperor or locate the recording. Senior officers did not give the coup the backing needed to succeed. The conspirators eventually withdrew, allowing the recording to be broadcast at noon on 15 August.
The incident is also called the Imperial Palace incident. It is distinct from the February 26 Incident of 1936, another attempted military uprising in Japan. The Kyūjō incident shows that the surrender announcement was not simply an uncontested administrative decision; hardline officers still hoped to continue the war.