The failed Japanese military coup attempt before Hirohito’s surrender broadcast was the Kyūjō incident.
The coup began on the night of August 14–15, 1945, when army officers opposed to surrender tried to seize the Imperial Palace. Their goal was to prevent the emperor’s recorded announcement from reaching the Japanese public and to continue the war.
The rebels searched for the recording, but palace staff hid the records successfully. They also attempted to control broadcasting facilities, yet the plot lost support from senior commanders and collapsed before morning. The recording was then transmitted at noon on August 15.
The incident is sometimes confused with earlier Japanese military revolts, especially the February 26 Incident of 1936. Unlike that earlier uprising, the Kyūjō incident occurred during the final hours of World War II and directly targeted the surrender broadcast.