The failed Japanese military coup attempting to stop Hirohito’s surrender broadcast was the Kyūjō incident.
Hardline Army officers launched the coup attempt on the night of August 14–15, 1945. They sought to prevent the recorded speech announcing Japan’s acceptance of the Allied terms from reaching the public. The plotters occupied parts of the Imperial Palace and searched for the recording.
The recording was hidden and preserved overnight. The coup failed after senior officers refused to support it, and Emperor Hirohito’s address was broadcast at noon on August 15. The incident showed that surrender was contested within Japan’s military leadership even after the Emperor had decided to accept the Allied conditions.
The event is also called the Imperial Palace incident. It should not be confused with the February 26 Incident of 1936, another attempted military coup in Japan. The Kyūjō incident occurred in the final hours before the surrender announcement and did not prevent the broadcast.