The Ocean Island massacre occurred on 20 August 1945 when between 150 and 200 civilians were killed in a mass execution by members of a Japanese naval garrison unit. The civilians, all originally inhabitants from other parts of the Gilbert Islands, had been brought to Ocean Island as slave labour.^[1][2] Perpetrated five days after the official Japanese announcement of surrender at the end of the Second World War, the nature of the massacre was only revealed four months later due to the emergence of a sole survivor, Kabunare Koura of Nikunau, who had remained in hiding until December 1945.^[3][4] Initially, the commander of the unit, Suzuki Naoomi, claimed that the civilian population had been killed during a rebellion, but the revelation of Kabunare's testimony and subsequent confessions from lower ranking participants led to war crimes prosecutions by the Australian military. In total, 21 Imperial Japanese Navy (IJN) personnel were convicted, of whom eight, including Naoomi, were executed, for their roles in the mass atrocity.^[5][6]

^‡ On the recommendation of the Judge Advocate General, death sentence was commuted to a prison term of 20 years.^[6]

* Lieutenant-commander Suzuki's execution was delayed due to appearing as a witness in the trial of Major General Hirota Akira.^[15]

• Japanese occupation of the Gilbert Islands
• Japanese occupation of Nauru
• Japanese war crimes