The failed Japanese military coup attempted before Hirohito’s surrender broadcast was the Kyūjō Incident.
The Kyūjō Incident took place during the night of August 14–15, 1945. Officers opposed to surrender tried to seize the Imperial Palace, prevent the broadcast, and locate the recording of Hirohito’s speech.
The plotters wanted to continue the war rather than accept the Allied terms. They occupied parts of the palace and attempted to obtain support from senior military leaders, but the coup lacked the necessary authorization and collapsed by the morning.
Palace officials had hidden the phonograph records containing Hirohito’s recorded message. The records were recovered after the coup failed and delivered to NHK, allowing the broadcast to proceed at noon on August 15. The incident is sometimes confused with the February 26 Incident of 1936, an earlier revolt by army officers that also involved an attempted seizure of government power.