High Quality Content by WIKIPEDIA articles! The Battle of the Hongorai River took place during the Second World War and involved Australian, New Zealand and Japanese forces. Part of the wider Bougainville Campaign of the Pacific theatre, the battle was fought in the southern sector of Bougainville Island and occurred in two distinct periods between 17 April and 22 May 1945, as elements of the Australian 15th Brigade advanced along the Buin Road towards the Hongorai River and then forced their way across it. Following the end of the initial fighting, the Australian advance towards the main Japanese concentration at Buin continued, however, torrential rain and flooding brought it to a halt, washing away many bridges and roads upon which they relied for supplies. With hostilities coming to a close the Japanese began harassing the Australian line of communications, and as the rain stopped and the flooding subsided in late-July and into August, preparations to resume the advance continued. Ultimately however, the war came to an end before the final Australian advance began.