The Battle of Finschhafen was part of the Huon Peninsula campaign in New Guinea during World War II and was fought between Australian and Japanese forces. The fighting took place between 22 September and 24 October 1943 following the landing at Scarlet Beach, which was followed by a two-pronged advance on Finschhafen as the Australian 20th Infantry Brigade advanced on the town from the north, while the 22nd Infantry Battalion drove from the south, having advanced from the landing beaches east of Lae. After the capture of Finschhafen, the Japanese forces in the area withdrew towards Sattelberg where they sought to hold the Australians before launching a counteroffensive, which subsequently threatened the landing beach. This attack was repelled by Australian and American forces, with heavy casualties being inflicted on the Japanese. In the aftermath, the Australians went on the offensive, capturing Sattelberg, and then advancing towards the Wareo plateau.

The 51st Division was an infantry division of the Imperial Japanese Army. Its call sign was the Base Division . It was formed on 10 July 1940 at Utsunomiya, Tochigi, simultaneously with 52nd, 54th, 55th, 56th, and 57th divisions. The 51st Division was initially assigned to the Eastern District Army and placed under command of Lieutenant General Kenichiro Ueno.