'Oboe III' was an Allied unrealised plan for Major General George F. Wootten’s Australian 9^th Division of Lieutenant General Sir Leslie Morshead’s Australian I Corps to land one infantry brigade at Banjarmasin, toward the eastern end of the south coast of Japanese-occupied Borneo (May 1945).

The object was to take airfield area, from which the planned 'Oboe IV' could be supported, unless British aircraft carriers were available for this task. The operation was cancelled for lack of the shipping which would have been required.

Banjarmasin was established in the 17^th century as a Dutch trading post on the mouth of the Barito river, the largest waterway in Borneo. By December 1941 the port was the capital of Dutch Borneo and its trade centre with a thriving export trade in copra, timber and rubber from a large and wild hinterland. The city was subject to flooding, and was therefore protected by many dikes, and large numbers of its buildings were constructed on pilings. Coal was also mined in the area, and the population in 1941 was about 65,600 persons.

On the outbreak of the Pacific War of World War II, the town was garrisoned by the South and East Borneo Territorial Command, equivalent to about a battalion of militia with a strength of 500 men. The town fell on 9 February 1942 to one battalion of the 146^th Regiment of Lieutenant General Masao Watanabe’s 56^th Division, which arrived overland from Balikpapan, and was met by a small group which had moved round the coast in barges to execute a pincer manoeuvre against the town. The operation was improvised in response to the US naval victory in the 1^st Battle of Balikpapan. The Dutch garrison attempted to effect the demolition of facilities, but were hindered by the desertion of most of their indigenous troops.

General Douglas MacArthur proposed the recapture of the town, but the plan were opposed by General Sir Thomas Blamey, the commander-in-chief of the Australian Military Force and commander-in-chief of the Allied Land Forces, South-West Pacific Area, and the town thus remained under Japanese control for the rest of the war.