Borneo is the third largest island in the world, after Greenland and New Guinea. In 1941, it was divided between Britain and the Netherlands, with Britain controlling most of the northwest coast, including the sultanate of Brunei, a British protectorate.
Geologically, Borneo is near the southeast extremity of the Asian continent, with the Indonesian island arc marking the boundary with the Indian Ocean plate to the south and the confused boundary with the Australian plate to the east. Its geology remains largely unmapped even at the start of the 21st century, but there are indications that the island is geologically ancient and stable, with a core resembling the highlands of southern Africa.
The coastal regions of Borneo are younger sedimentary beds accreted onto the island core, and it is here that mineral wealth was found in the form of oil. Large oil fields were in production at Miri, Seria, and Lutong in or near Brunei on the northwest coast; at Sandakan, Tarakan, and Balikpapan along the east coast; and at Kuching and Pontianac on the west coast. Borneo crude oil was light enough to be burned directly in ship's boilers, without refining, but when the Japanese turned to this expedient late in the war, they found that the sulfur content was high enough to make boiler steel brittle, eventually ruining the boilers.
The oil fields and military facilities of Borneo were important Japanese war objectives in 1942, the latter as stepping stones to Java. The Japanese strategy was to leapfrog down the coast, capturing airfields and ports from which they could cover the next stage of their advance.
The opening stages of the Borneo campaign took place along the
northwest coast and were conducted primarily by elements of 55
Brigade Group and 2 Yokosuka Special Naval Landing Force.
The initial landings took place at Miri
on 15-16 December 1941 and were followed up by landings at Kuching on 24 December, Jesselton on 8 January 1942, and Sandakan on 17 January.
Once west Borneo and Davao were secured, the Japanese were ready to begin leapfrogging down the east Borneo coast. The forces involved here were primarily 56 Brigade and 2 Kure Special Naval Landing Force. Initial landings were at Tarakan on 11 January 1942, and were followed by landings at Balikpapan on 23-24 January and Banjarmasin on 10 February.
The only significant Allied success during this campaign was at Balikpapan, where a squadron of U.S.destroyers surprised a Japanese invasion convoy at anchor and managed to sink several ships before withdrawing without loss. This upset the Japanese timetable by perhaps a day.
The second Borneo campaign took place in the last months of the
Pacific War and is controversial. Conducted by Australian troops under MacArthur's command, it
was seen as relegating these superb troops to an unnecessary backwater
campaign, conducted more for the political purpose of demonstrating
Western military power to the people of southeast Asia than for any
military purpose. The campaign was conducted primarily by elements of
the Australian
I Corps.
Oboe I was a landing at Tarakan conducted by the Australian 26
Brigade on 1 May 1945. Oboe II was conducted by Australian 9 Division,
which seized Brunei (10 June) and Miri (20 June). Oboe VI was conducted
by Australian 7 Division
on 1 July 1945, seizing Balikpapan. It was the
last amphibious
operation of the war.
References
The Pacific War Online Encyclopedia (c) 2007-2008 by Kent G. Budge. Index
