'B' (ii) was the Japanese seizure of the island of Borneo in the British and Dutch East Indies (16 December 1941/1 April 1942).

Measuring some 600 miles (970 km) in length and 500 miles (800 km) in width, Borneo is the third largest island in the world, with a total area of 287,000 sq miles (743330 km²). In 1941 the island was divided between the UK and the Netherlands, with the former ruling most of the north-western coast, which was divided into the sultanates of Sarawak and Brunei, both British protectorates, and British North Borneo. In geological terms, Borneo lies near the south-eastern extremity of the Asian continent, with the island arc of the Netherlands East Indies marking the boundary with the Indian Ocean plate to the south and the confused boundary with the Australian plate to the east.

The interior of Borneo is mountainous, especially in the north, with Mt Kinabalu reaching a height of 13,435 ft (4095 m). The coastal regions are younger sedimentary beds added onto the island’s core, and it is here that mineral wealth, in the form of oil, is found. In 1941 large oilfields were in production at Miri, Seria and Lutong in or near Brunei on the north-western coast; at Sandakan, Tarakan and Balikpapan along the eastern coast; and at Kuching and Pontianac on the western 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 oil’s sulphur content was high enough to render boiler steel brittle, eventually ruining the boilers.

There are several large rivers, but these are difficult to navigate as a result of their ever-changing bars. The rivers nevertheless provided the only communications to many interior villages, where most of the island’s rice was grown. The south and west coasts are fringed by extensive mangrove swamps.

The Dutch portion of the island had a population of about 2.23 million persons, of whom 6,000 were Europeans, 2.1 million Indonesians of at least six ethnicities, 140,000 Chinese, and 13,000 others. British North Borneo had a population of 252,000 Malayans, 50,000 Chinese, and a small number of Europeans, while Sarawak had a population of 490,600. Brunei had a population of just 39,000. The road network was limited to the immediate vicinity of Banjarmasin, Balikpapan and Pontianac, and these were not interconnected.

The 'B' (ii) undertaking was essentially the first phase of Japan’s primary objective in entering World War II to establish a 'Greater East Asia Co-Prosperity Sphere', namely the seizure of the resources-rich 'Southern Resources Area' centred on the Dutch East Indies which, among its other resources, had a major oil industry and also large stocks of refined oil products. The Japanese reckoned that the advantages of seizing and holding this vital resources area, together with the area that flanked this southward expansion on the east and west, more than offset the dangers of committing Japan to war with the Netherlands, the UK and the USA.

The oil fields and military facilities of Borneo were therefore important objectives for the Japanese in 1941, and the island was also in itself a significant stepping stone in the planned route 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.

Japanese intelligence estimated that the British had 70,000 men and 320 aircraft in Malaya and 35,000 men and 60 aircraft in Burma on Malaya’s north-western flank abutting India, the Americans 42,000 men and 170 aircraft in the Philippine islands group on the eastern flank of the planned offensive, and the Dutch 85,000 men and 300 aircraft in the East Indies that were the primary objective for their oil and abundant supplies of several strategic raw materials. However, the Japanese also reckoned that this overall strength of 232,000 men and 850 aircraft, supported by not insignificant naval forces, was of generally indifferent quality. The Japanese understood that many of the army formations were 'colonial' and thus poorly trained, equipped and motivated, the aircraft were obsolete, and the majority of the ships also of second-line quality.

In this circumstance, therefore, the Japanese believed that 'B' (ii) against Borneo, 'H' (i) against Celebes, 'J' (ii) against Java, and 'L' (i) against south-eastern Sumatra, together with 'M' (i) against the Philippines, 'E' (i) against Malaya and 'B' (iii) against Burma, could be accomplished by comparatively small forces possessing the advantage of altogether higher quality and considerable combat experience at all levels. Thus the Japanese expansion to the south was to be undertaken by 11 army divisions and a number of army and naval special forces totalling 200,000 men, 700 army and 1,600 navy first-line aircraft supported by 1,500 army and 3,300 navy reserve aircraft, and naval forces which were superior to those of the Allies in numbers as well as in quality. Moreover, the Japanese believed that so long as they retained the strategic initiative, they could use their greater maritime capability to ensure local superiority of force to ensure victories that were both complete and, just as importantly, swift so that men and equipment could them be switched to other areas if required.

Another element rated very highly in the Japanese plans was complete air superiority over the land battlefield, largely through the range capabilities of their two most important naval aircraft types, the supremely agile and well-armed Mitsubishi A6M Reisen 'Zero' single-engined fighter and the high-performance Mitsubishi G4M 'Betty' twin-engined medium bomber.

The Japanese tactics in this important campaign were at the same time aggressive and cautious. Once an objective (usually a port with an airfield in its vicinity) had been selected, the Japanese concentrated their land-based air power on attacking and destroying any Allied air units based on the airfield. With that preliminary task accomplished, a naval task force including at least one aircraft carrier, but almost always operating under the cover of land-based aircraft, landed sufficient army or navy troops to overwhelm the local Allied garrison and seize the airfield. Once this latter had been returned to operability, land-based aircraft were moved forward to this new base, and the whole process could then be repeated.

As noted above, in 1941 Borneo comprised Dutch and British colonies. The so-called 'White Rajahs' of the Brooke family had ruled Sarawak, in north-western Borneo, for more than one century, first as rajahs under the Sultanate of Brunei (a tiny but once powerful state entirely enclosed within the borders of Sarawak), and from 1888 as a British protectorate. The island’s north-eastern region comprised North Borneo, since 1882 another British protectorate under the British North Borneo Company, and off its coast the small British crown colony of Labuan. The rest of the island, collectively known as Kalimantan, was under Dutch control. In overall terms, therefore, the north-western third of this basically triangular island comprised the British colonies of North Borneo and Sarawak, and the south-eastern two-thirds parts of the Netherlands East Indies.

The Netherlands East Indies possessed their own armed forces, the Koninklijk Nederlands Indisch Leger (Royal Netherlands East Indies army) under the command of Generaal-majoor Hein ter Poorten and comprising some 35,000 troops, of whom 28,000 were indigenes (with about one Dutch officer or non-commissioned officer to 40 native soldiers) as well as a large reserve and home guard of both Dutch and indigene personnel. The total regular, reserve and territorial strength was some 85,000 men. The regular troops were well trained and disciplined, but the Reservekorps and Landstorm reserves and the Stadswacht home guard were considerably less effective. The Dutch had also started to raise an Indonesian militia in June 1941. Much of weapons and equipment operated by these forces was obsolescent, and units were often under-equipped.

A battalion-sized detachment of the Koninklijk Nederlands Korps Mariners (Royal Netherlands marine corps) was attached to the Royal Netherlands East Indies army.

The Militaire Luchtvaart (air force) had 140 obsolescent US-made fighters and light bombers as well as 80 reconnaissance, light transport and trainer aircraft. Most of the aircraft were based on Java, and were under the command of Generaal-majoor Ludolph Hendrik van Oyen.

There were three components of the Zeemacht Nederlands-Indië (Netherlands Indies sea forces) under the command of Vice-admiraal Conrad E. L. Helfrich, and these were based mostly at Soerabaja (Surabaya) on the island of Java, the principal naval base: these components were the Nederlands Indië Marine (Netherlands Indies navy) with 10 mine warfare vessels, 15 coastal submarines, and a patrol boat; the Nederlands Indië Eskader (Netherlands Indies squadron) with four light cruisers and seven destroyers commanded by Schout-bij-nacht Karel W. F. M. Doorman; and the Gemilitairiseede Gouvernementsmarine (militarised government navy) which was essentially a customs and patrol service with 15 patrol boats.

In 1940 Japan was the fourth largest importer of oil, raw materials and goods from the Netherlands East Indies after the USA, Malaya and the UK. In September of that year Japan started to exert pressure of the Netherlands East Indies' government for a greater quantity of deliveries, especially of oil, and announced to the Netherlands East Indies' government’s anger that its 'Greater East Asia Co-Prosperity Sphere' now included the Netherlands East Indies.

In the same month Japanese troops entered French Indo-China in 'Fu'. In January 1941 a small-scale war broke out between French Indo-China and Thailand, and Japan negotiated a peace settlement.

Amid growing concerns of Japanese expansionism, US, British, Australian, New Zealand and Dutch officials met secretly in Singapore during April to discuss security matters of mutual concern. The British proposed to hold Singapore at all costs, and that the USA reinforce the Philippine islands group so that they could launch attacks on Japan in event of war, and also provide military aid to the Netherlands East Indies. The USA agreed to none of the proposals and agreed only to continue the flow of its aid to China.

On 10 May 1940 Germany invaded the Low Countries and France in 'Sichelschnitt', and the Netherlands surrendered five days later, although the Netherlands East Indies remained autonomous. Vichy France agreed to place Indo-China under combined Japanese and French protection in July. The Netherlands East Indies responded by cancelling all exports to Japan and freezing Japanese bank accounts, as did the UK.

Admiral Sir Thomas Phillips’s small British Eastern Fleet and Admiral Thomas C. Hart’s US Asiatic Fleet were provided with minor reinforcements, but little else was done. There were 65,000 British, Indian and Australian troops in Malaya and Singapore. Australia provided two infantry battalions to reinforce the small Dutch garrisons on Amboina and Timor. There were other Dutch garrisons on some of the larger islands, including Sumatra and Borneo, but most of the Dutch forces were concentrated on Java. An Indian battalion garrisoned British Borneo.

Following the Japanese 'Ai', 'M' (i) and 'E' (i) attacks on Pearl Harbor, the Philippine islands and Malaya, the government of the Netherlands East Indies declared war on Japan and interned all Japanese citizens.

On 9 December the British battleship Prince of Wales and battle-cruiser Repulse, constituting Phillips’s Force 'Z', were spotted and reported by the Japanese submarine I-58 and then attacked and sunk in the South China Sea by bombers of Rear Admiral Sadaichi Matsunaga’s 22^nd Air Flotilla operating from bases just to the north of Saigon in French Indo-China, thus leaving the Allies without any capital ship force in the Pacific.

The Japanese invaded British Borneo on 16 December, and the first Dutch territory seized by Japan was the tiny Tamelan islands group between Borneo and Singapore on 27 December.

The American-British-Dutch-Australia Command (ABDACOM) was established on 15 January 1942 at Batavia on Java to co-ordinate the defence of Burma, the Philippines, the Netherlands East Indies and the north-western approaches to Australia. The remnants of the US Asiatic Fleet were ordered to Java from the Philippine islands at the end of December. The main goal of this combined command was to establish the so-called 'Malay Barrier', some 3,500 miles (5630 km) long, following the Malay peninsula’s mountain chain and through the East Indies to western New Guinea. The ABDACOM was led by a British officer, General Sir Archibald Wavell, with a US officer, Lieutenant General George H. Brett, as his deputy. Hart commanded the naval forces based at Soerabaja, and a British officer, Air Marshal Sir Richard Peirse, controlled the air forces. ABDACOM’s forces were too diverse, too widely spread and too few in number for the task demanded of them, and their problems were further compounded by wholly inadequate logistics but, and most importantly, too little time to develop and implement any effective defence.

The disparity between the opposing forces can be demonstrated by the regional naval strength at the outbreak of hostilities, at which time the Allies had 94 warships and the Japanese 230 warships. Besides weakness of forces and limited unity of command, the Malay Barrier possessed another serious flaw inasmuch as it provided no defence in depth. If the Japanese penetrated the weak forward defence, the only positions on which the Allies could fall back were Australia and India.

The Japanese 'B' (ii) conquest of the Netherlands East Indies was scheduled to begin on 11 January 1942, and while they had established no fixed schedule, the Japanese estimated that the task would be completed within 150 days.

In overall terms the Japanese goals were the defeat of the Allied forces in Malaya, Burma, the Philippine islands group and the Netherlands East Indies; the establishment of control of the economic resources of the so-called 'Southern Resources Area' (especially Malaya and the Netherlands East Indies); and the creation of a southern defence zone through the Netherlands East Indies, whose oil was of primary importance to the Japanese war effort inasmuch as Japan had received 80% of its oil from the USA and this source ended with the US embargo imposed during July 1941.

The Japanese forces allocated to the task of taking the Netherlands East Indies were controlled by General Count Hisaichi Terauchi’s Southern Expeditionary Army Group, which had its headquarters at Saigon in Japanese-occupied French Indo-China. Air support would be provided by Lieutenant General Michio Sugawara’s 3^rd Air Group (from 15 April 1942 3^rd Air Division), also headquartered in Saigon. The Southern Expeditionary Army Group was responsible for operations in the Philippine islands group, Thailand, Burma, the eastern part of New Guinea, and the Netherlands East Indies.

The seizure of the Netherlands East Indies was allocated to three groups of forces: the Western Force staging from Cam Ranh Bay in Japanese-occupied French Indo-China and directed at British Borneo, Sumatra and the western part of Java; the Central Force staging from Davao in the Japanese-occupied island of Mindanao in the Philippine islands group and directed at Dutch Borneo; and the Eastern Force also staging from Davao and directed at Celebes, Amboina and Timor islands.

Lieutenant General Hitoshi Imamura’s 16^th Army was the primary formation for the Netherlands East Indies campaign, but two other armies also involved were Lieutenant General Tomoyuki Yamashita’s 25^th Army, mainly responsible for Malaya but also tasked with the capture of Sumatra, Borneo and Celebes, and Lieutenant General Masaharu Homma’s 14^th Army which would send elements from the Philippine islands group to support the 25^th Army's operations on Borneo and Celebes.

Vice Admiral Nobutake Kondo’s 2^nd Fleet was to provide the required naval support.

The formations assigned to tasks in the Netherlands East Indies were therefore the 16^th Army deployed from Japan with Lieutenant General Masao Maruyama’s 2^nd Division (4^th, 16^th and 29^th Regiments as well as the 2^nd Field Artillery Regiment), Lieutenant General Yuitsu Tsuchihashi’s 48^th Division (1^st and 2^nd Formosa Regiments, 47^th Regiment and 48^th Mountain Artillery Regiment) released by the 14^th Army, and Major General Shizuo Sakaguchi’s 'Sakaguchi' Detachment (56^th Infantry Group based on the 146^th Regiment of Lieutenant General Masao Watanabe’s 56^th Division) also released by the 14^th Army; and the 25^th Army which released for Netherlands East Indian operations Lieutenant General Akira Muto’s Guards Division (2^nd, 4^th and 5^th Guards Regiments as well as the Guards Field Artillery Regiment), Lieutenant General Tadayoshi Sano’s 38^th Division (228^th, 229^th and 230^th Regiments as well as the 38^th Mountain Artillery Regiment) from Hong Kong, and Major General Kiyotake Kawaguchi’s 'Kawaguchi' Detachment (35^th Brigade based on the 124^th Regiment of Lieutenant General Renya Mutaguchi’s 18^th Division) from French Indo-China.

The Tripartite Pact signed on 27 September 1940 between Germany, Italy and Japan guaranteed mutual support between the three signatories, and yielded an important dividend for Japan in July 1941 when, as noted above, the Vichy French regime ceded effective control of French Indo-China to Japan. This gave Japan land further access to the Chinese mainland where it had long been engaged in military intervention and, since 1937, had been fighting a full war against the temporarily allied Chinese forces of the Kuomintang nationalist party and the Chinese communist party. It also gave Japan a coast facing Sarawak and North Borneo across the China Sea.

At this time Japan was increasingly refocusing its gaze from the war in China toward strategic targets in the Pacific and the Netherlands East Indies, and in December launched its 'Ai' undertaking against US military forces and installations in Hawaii, and also its 'M' (i) undertaking on the Philippine islands group, declaring war on the USA and also precipitating Germany’s and Italy’s declarations of war on the USA during 11 December.

Within this revised focus, the rich oil resources, especially at Tarakan, Balikpapan and Bandjermasin, made Borneo a key target for Japan, but also one that was very indifferently held. Chronically short of natural resources, Japan needed an assured supply of fuel to achieve its long-term goal of becoming the major power in the Pacific region. Borneo also stood on the main sea routes between Japan and the rest of the East Indies, and also between Java, Sumatra, Malaya and Celebes. Control of these routes was vital to securing the territory.

The main objectives in northern Borneo were the oilfields at Miri in Sarawak and at Seria in Brunei, and the associated refinery at Tutong near Miri.

Despite its strategic importance, the Sarawak region had neither air nor sea forces to protect it. Only at a time late in 1940 did Air Chief Marshal Sir Robert Brooke-Popham, the British commander-in-chief in the Far East, order the 2/15^th Punjab Regiment, a battery of 6-in (152-mm) guns of the Hong Kong-Singapore Royal Artillery, and a detachment of the 35^th Fortress Company, Royal Engineers, totalling about 1,050 men, to be positioned at Kuching. In addition, the Brooke régime also organised the Sarawak Rangers of 1,515 men largely from the Iban and Dyak tribes. Altogether these forces were commanded by a British officer, Lieutenant Colonel C. M. Lane, and known as 'Sar' Force (Sarawak Force).

After learning on 8 December of the 'Ai' attack on Pearl Harbor, the Brooke regime ordered that the oilfields at Miri and Seria and the refinery at Tutong should be demolished as a matter of urgency.

Off to the south-east, the Dutch forces had an important airfield at Singkawang called 'Singkawang II', defended by about 750 Dutch troops. The Dutch Naval Aviation Group GVT-1 with three Dornier Do 24K three-engined flying boats was located in Pontianak along with a 500-man army garrison under the command of Luitenant-kolonel Dominicus P. F. Mars. The Dutch forces in western Borneo consisted of the West Borneo Garrison Battalion, the Stadswacht Infantry Company (about 125 men) in Pontianak, an anti-aircraft battery with two 40-mm guns and some machine guns, a mobile auxiliary first aid platoon, a Stadswacht detachment of some 50 men in Singkawang, and a Stadswacht detachment of unknown strength in Sintang.

It was on 29 January that Pontianak fell to Japanese units from the Canton area in the south of China. This 'Kawaguchi' Detachment of the Western Force had some 4,500 men in the form of the headquarters of the headquarters of the 35^th Brigade, 124^th Regiment of the 18^th Division, 2^nd Yokosuka Naval Landing Force, 4^th Naval Construction Unit, one platoon of the 12^th Engineer Regiment, one unit of the 18^th Division Signal Unit, one detachment of the 18^th Division Medical Unit, 4^th Field Hospital of the 18^th Division, and one unit of the 11^th Water Supply and Purification Unit.

On 13 December 1941, the Japanese invasion convoy of 10 transports had left Cam Ranh Bay in French Indo-China under escort of a force, commanded by Rear Admiral Shintaro Hashimoto, comprising the light cruisers Kinu and Yura, destroyers Murakumo, Shinonome, Shirakumo and Usugumo of the 12^th Destroyer Division, submarine chaser Ch-7, minesweepers W-6 and W-7, and aircraft depot ship/seaplane tender Kamikawa Maru. Support was provided by Rear Admiral Takeo Kurita’s force comprising the heavy cruisers Kumano and Suzuya, and the destroyers Fubuki and Sagiri.

More distant cover for 'B' (ii) and 'E' (i) was provided by Kondo’s 2^nd Fleet comprising the battleships Haruna and Kongo, the heavy cruisers Atago and Takao, and the destroyers Arashio, Asashio, Ikazuchi, Inazuma, Michishio and Oshio.

The main part of the Japanese strength was to take Miri and Seria, while the rest took Kuching and nearby airfields. The convoy proceeded without detection, and at dawn on 16 December 1941 two landing units secured Miri and Seria with only very little resistance from the British-led forces before, only a few hours later, capturing Lutong.

Meanwhile, on 31 December 1941, a force under Lieutenant Colonel Watanabe progressed northward for the occupation of Brunei, Labuan island and Jesselton. Transported in small fishing boats, the Japanese landed at Sandakan, the seat of government of British North Borneo, on 18 January 1942. The North Borneo Armed Constabulary, with only 650 men, could offer only the most limited resistance in an effort to slow the Japanese advance. On the morning of the 19 January, Charles Robert Smith, the governor, surrendered British North Borneo.

After securing the oilfields, on 22 December, the main Japanese forces moved to the south-west in the direction of Kuching, and Japanese aircraft bombed 'Singkawang II' airfield to prevent a Dutch counterattack. After a minor delay occasioned by the appearance of a Dutch submarine, the Japanese naval force approached the mouth of the Santubong river on 23 December, and the troop convoy arrived off Cape Sipang. Commanded by Colonel Akinosuke Oka, the men carried in 20 transport ships started to land at 04.00 on 24 December. Although the 2/15^th Punjab Regiment resisted the attack, it was outnumbered and soon compelled to retreat up the river. By the afternoon, Kuching was in the hands of the Japanese. At about 16.40 on 25 December, the Japanese took Kuching airfield, and the men of the 15^th Punjab Regiment retreated through the jungle to the area of Singkawang.

After the Japanese had moved forward to take Singkawang on 29 December, the surviving British and Dutch forces retreated farther inland into the jungle, moving to the south in an effort to reach the area of Sampit and Pangkalanbun, where a Dutch airfield was located at Kotawaringin.

South and central Kalimantan were taken by Japanese naval forces in attacks from east and west. After 10 weeks in the jungle-covered mountains, the Allied troops surrendered on 1 April 1942, leaving the north-western part of Borneo in Japanese hands.

On the eastern side of the island, the battle for Tarakan took place on 11/12 January 1942. Even though Tarakan was only a small marshy island off the north-eastern coast of Borneo, its 700 oil wells, oil refinery and airfield together constituted one of the main objectives for Japan in the Pacific War.

Japan in fact declared war on the Netherlands on 10 January 1942 although fighting between Japanese and Dutch forces had already lasted for one month in other parts of Borneo, and Queen Wilhelmina of the Netherlands had declared war on Japan on 8 December 1941.

The 'Sakaguchi' Detachment of the Central Force comprised the headquarters of the 56^th Regimental Group, one company of tankettes, the reinforced 146^th Regiment, the 1/56^th Field Artillery Regiment, one company of the 56^th Engineer Regiment, one company of the 56^th Transport Regiment, infantry elements of the 2^nd Kure Special Naval Landing Force, the 2^nd Oilfield Construction Unit, and the 5^th Airfield Construction Unit. The opposing Dutch forces comprised the Tarakan Garrison Battalion (7^th Netherlands East Indies Battalion), a motorised detachment with seven armoured cars, the 3^rd Coastal Artillery Regiment with two mobile batteries with three 75-mm (2.95-in) and two 70-mm (2.76-in) guns, five static coastal artillery batteries with two 120-mm (4.72-in), 10 75-mm (2.95-in) and three 37-mm guns, two anti-aircraft batteries with four 40-mm and four 20-mm guns, and four anti-aircraft machine gun platoons each with three 12.7-mm (0.5-in) machine guns, two engineer platoons, and one mobile auxiliary first aid platoon.

On 10 January 1942 a Dutch Do 24K flying boat spotted the oncoming Japanese invasion fleet and, appreciating that his forces had only the smallest chance of prevailing in the forthcoming battle, the Dutch commander ordered the destruction of all of the island’s oilfields and facilities. The right wing of the 'Sakaguchi' Detachment (5,500 infantry and 1,100 marines), supported by a force of 15 destroyers, landed on the eastern coast of Tarakan at 00.00 on 11 January, followed by the 2^nd Kure Special Naval Landing Force. After mounting a brief but fierce resistance, the outnumbered Dutch garrison surrendered on the morning of 12 January after the Japanese had suffered 255 men killed. The survivors of the 1,300-man Dutch garrison forces were executed by the Japanese in retaliation for the destruction of the oil installations, and this war crime was later repeated at Balikpapan.

During the night of 11/12 January, before the Japanese forces had completed their blockade of Tarakan, two Dutch naval units (submarine K-X and patrol boat P-1) as well as the civilian motor launch Aida had managed to slip away. The Dutch minelayer Prins van Oranje and patrol boat P-38 also tried to escape, but were sunk by the Japanese destroyer Yamakaze.

Farther to the south along the south-eastern side of Borneo, the battle for Balikpapan took place on 23/24 January near the major oil producing town and port of Balikpapan. After capturing the oilfields at Tarakan, Sakaguchi’s forces moved forward to Balikpapan in the hope of taking the oilfields and their associated installations before the Dutch could destroy them. The Dutch forces in and around Balikpapan numbered about 1,100 men under the command of Luitenant-kolonel C. van den Hoogenband. The town was protected by coastal, field and anti-aircraft artillery batteries, and the entrance of the harbour was protected by a minefield laid by the minelayer Soemenep. On 18 January van den Hoogenband ordered the destruction of the oilfields in Balikpapan and started to evacuate non-essential personnel to Samarinda. The demolition of the oilfields was not completed, however, and the only serious damage was to the storage tanks, pipes and special quays in the harbour area.

On 22 January Japanese transport vessels and warships were spotted as they moved south, and on 24 January Dutch bombers attacked the convoy. Despite this, at about 20.00 the Japanese landed about 3.1 miles (5 km) to the south-east of Balikpapan airfield. The assault met no Dutch resistance and, by dawn, had occupied the airfield. The Japanese southward advance moved slowly as the bridges had been destroyed, and the leading Japanese units reached the northern outskirts of Balikpapan only on the night of 25 January, by which time the garrison had been withdrawn to the interior of Borneo, so the Japanese were able to enter Balikpapan without a fight. After Balikpapan had been occupied, an infantry detachment commanded by Lieutenant Colonel Kume was ordered to protect the oilfields.

The main strength of the Japanese force and its supporting transports and warships, the latter comprising 15 destroyers, then moved to the south under Sakaguchi to take Bandjermasin on the southern coast of Kalimantan, an area rich in oil, rubber, timber and coal. The Japanese plan was to develop Bandjermasin as the primary base for further advances, in this instance the north coast of Java. During the afternoon of 23 January, nine Dutch Martin Model 166 twin-engined light bombers attacked the Japanese convoy. The transport ship Tatsugami Maru was damaged and Nana Maru was sunk. Near Balikpapan, the Dutch submarine K-XVIII attacked and sank another transport, Tsuruga Maru, and reportedly damaged the patrol boat P-37.

While the Japanese invasion force was landing at Balikpapan, at about 02.45 on 25 January, the US Navy’s 59^th Destroyer Division, under the overall command of Rear Admiral William A. Glassford and tactical command of Commander Paul H. Talbot, attacked the Japanese navy escort led by Rear Admiral Shoji Nishimura for about four hours. The US destroyer force comprised Paul Jones, Parrott, Pope and John D. Ford, and concentrated its efforts primarily on the 12 Japanese transport ships. At least three of the latter (Kuretake Maru, Sumanura Maru and Tatsukami Maru) and the patrol boat P-37 were sunk in torpedo attacks. However, most of the torpedoes launched by the Allied destroyers missed their targets or did not detonate.

Moreover, since the landing had already taken place, at about 21.30, the raid was ineffective in stopping the capture of Balikpapan.

The attack on Bandjermasin was effected by the concentration of Colonel Kyohei Yamamoto’s 146^th Regiment with naval support led by Captain Yoshibumi Okamoto. The land force started to move on 30 January, and the naval support had departed three days earlier. Although the land force had to cross the dense jungle and faced tropical heat and rain, it soon occupied small towns of Moera Oeja, Bongkang, Tandjoeng, Amoentai, Barabai, Kandangan and Rantau. The sea force moved only at night and launched surprise attack against Kotabaru on Laut island.

After occupying Martapura airfield, the Japanese took Bandjermasin without a fight on 10 February, the Dutch under Lieutenant Colonel H. T. Halkema having retreated to defend Kotawaringin airfield in central Kalimantan. The battles for Borneo were only the first of those in which the Japanese took the Netherlands East Indies, and following battles were those of Manado, Ambon, Palembang, the Makassar Strait, the Badung Strait, the Java Sea, the Sunda Strait, Java and Timor.