'L' was the Japanese seizure of the south-eastern half of the island of Sumatra in the Netherlands East Indies as a major element of securing the 'Southern Resources Area' which Japan considered essential to its survival (13 February/28 March 1942).

Sumatra is the second largest island of what was at the time the Netherlands East Indies and is also the sixth largest island in the world, with an area of 182,812 sq miles (473481 km²). The Barisan Gebergte mountain chain extends the full length of the island’s Indian Ocean coast, and varies in height from 5,000 ft (1525 m) to 12,484 ft (3805 m), with the highest point at Mt Kerinji to the south-east of Padang. There is only a narrow coastal plain to the south-west of these mountains. The lower two-thirds of the island in the area to the north-east of the mountains is a broad alluvial plain covered by jungle and bordered by extensive swamps along the coast. The north-western one-third of the island has a much narrower coastal plain in the area to the north-east of the mountains, but this is free of swamps. There are several large rivers draining into the north-east coast, including the Musi river, which had a dredged channel for small ocean-going ships as far as upriver as Palembang, and the Hari river to its north-west, which had a navigable length of 300 miles (485 km).

In 1941 the island’s largest towns were Medan in the north, Palembang and Teleokbetoang in the south, and Padang on the Indian Ocean coast. The port of Sabang, a small island just off the western tip of Sumatra, was the westernmost port in the Netherlands East Indies.

The interior of the lower two-thirds of Sumatra, inland of the coastal swamps, was the primary agricultural region. Although the island had a significant road network, including a road along most of the south-west coast and roads crossing the mountains into the agricultural interior, most of the south-eastern two-thirds of the north-east coastal region was inaccessible by road, though there was a road and railway system along the northern one-third of the north-east coast. Another railway system connected Palembang with Teleokbetoang. The total railway milage was 1,139 miles (1833 km). There was a regular ferry from Teleokbetoang to Java, and there were also primitive telephone and telegraph systems connecting the major cities.

The population of Sumatra and neighbouring islands was about 2.3 million persons, of which some 6,000 were Europeans and 153,000 Asians (mostly Chinese) and Arabs.

Sumatra’s jungles made it difficult to access the island’s greatest source of wealth, the rich oil fields. Those around the city of Palembang had been in production since 1907, accounted for half the oil production of the Netherlands East Indies, and produced oil that was particularly rich in the valuable lighter fractions, such as petrol. There was also significant production of coal at Ombilin in the mountains to the north-east of Padang, at Boekit Asam to the south-west of Palembang, and in other localities, though most of coal production was for local use. The island also produced rubber and other agricultural products.

Palembang was assaulted by paratroops on 14 February 1942, who seized the oil fields and refinery before significant demolition could take place. Seizure of the rest of the island was completed by 28 March 1942.

The oil refineries of the Royal Dutch Shell company at Pladjoe on Sumatra were major objectives for Japan as a result of the oil embargo imposed on Japan by the USA, UK and the Netherlands. Given the abundance of oil and an airfield in the area, Palembang offered significant potential as a military base to both the Allies and the Japanese.

In January 1942 the ABDACOM (Australian, British, Dutch and American Command) decided to concentrate Allied air forces in Sumatra at just two of the island’s 14 airfields near Palembang, namely Pangkalan Benteng ('P1') some 8 miles (13 km) to the north of Palembang, and a secret air base at Praboemoelih ('P2') some 40 miles (65 km) to the south-south-west of Palembang. The British created No. 225 Group at Palembang, this group including two Australian squadrons and a large number of Australians serving with British squadrons, but in overall terms the eight squadrons of this group could muster only 40 Bristol Blenheim and 35 Lockheed Hudson light bombers. The Blenheim aircraft had flown from the Middle East and Egypt, where they were considered too old to cope with newer German and Italian fighters. (A handful of B-17 Flying Fortress heavy bombers, of Major General Lewis H. Brereton’s Far East Air Force of the USAAF, also operated out of Palembang briefly in January, but these were withdrawn to Java and Australia before the battle started.)

Air Commodore S. F. Vincent’s No. 226 Group of the RAF also arrived at Palembang early in February with two squadrons of Hawker Hurricane fighters transported to Sumatra by the aircraft carrier Indomitable, and at Palembang these were joined by the remnants of the RAF, RAAF and RNZAF Hurricane and Brewster Buffalo squadrons which had suffered heavy losses in the intense air battles over the Malaya and Singapore campaigns.

The Netherlands East Indies army’s forces in Sumatra were commanded by Major General Roelof Theodorus Overakker and comprised some 4,500 troops seven garrison battalions named for their bases (Fort de Kock, Medan, Permatansiantur, Padang, Sibolga, Jambi and Palembang). Though this was the second largest Dutch troop concentration in the Far East, it was totally inadequate to protect an island 1,000 miles (1600 km) long, and the battalions were scattered across the island, with the greatest concentration in the restive north rather than around the prize of Palembang in the south. In the island’s south-eastern half was the South Sumatra Island Territorial Command, the command organisation in the Palembang area, which comprised about 2,000 troops (with one machine gun company, one anti-aircraft battery and four artillery batteries) under Lieutenant Colonel L. N. W. Vogelesang, and these were the South Sumatra Garrison Battalion and a Stadswacht/Landstorm infantry company in Palembang, a Stadswacht/Landstorm infantry company in Jambi (Djambi), and various artillery and machine gun units.

The Dutch units in other parts of Sumatra lacked mobility and played no part in the fighting, and it was planned that Major General John D. Lavarack’s Australian 7^th Division would be deployed to the island from the Middle East, but no sooner than 21 March.

The Dutch naval strength in the area was based on the minelayer Pro Patria and the patrol boats P-38 and P-40 on the Musi river.

The Japanese planned a two-phase conquest of Sumatra: in the first, namely 'L' (i) starting in mid-February 1942, elements of the Western Force would overrun the south-eastern half of the island, and in the second, starting in mid-May 1942, elements of Lieutenant General Tomoyuki Yamashita’s 25^th Army would complete the seizure of Sumatra by overrunning the north-western half of the island in 'T' (i) and associated undertakings after the completion of their 'E' (i) conquest of Malaya.

The first Japanese air raid on Sumatra arrived on 6 February and attacked the 'P1' airfield, the Allies losing two Blenheim bombers and four Hurricane fighters, with another two other Hurricane fighters damaged. On the ground, the Japanese destroyed two Buffalo fighters. During the attack, the Allies shot down only a single Nakajima Ki-43 Hayabusa 'Oscar' fighter. As a countermove, the Allies began night raids against the Japanese lines on the Malay peninsula and provided air protection for refugee convoys from Singapore.

The main Japanese invasion force, an amphibious assault fleet under the command of Rear Admiral Shintaro Hashimoto, was meanwhile approaching from Cam Ranh Bay in French Indo-China, where the assault force had been assembled after leaving Hong Kong. The invasion force was centred on the 229^th Regiment and one battalion of the 230^th Regiment of Lieutenant General Tadayoshi Sano’s 38^th Division. A small advance party set out from Cam Ranh Bay, in Japanese-occupied Indo-China, in eight transports 1, and the main force followed on 11 February in 13 transports, escorted by the heavy cruiser Chokai and four destroyers of Vice Admiral Jisaburo Ozawa’s Western Covering Fleet. This covering force included the light aircraft carrier Ryujo under the command of Rear Admiral Kakaji Kakuta, four heavy cruisers, one light cruiser and three destroyers. Additional air cover was provided by land-based naval aircraft and the warplanes of the Japanese army air force’s 3^rd Air Division.

The Dutch tanker Manvantara was sunk by Japanese aircraft on 13 February 1942 in the Java Sea. Four Dutch submarines were lying in wait off the Anambas islands group, but these could not reach the Japanese fleet. The transports reached Singapore, and subsequently Allied refugee freighters which were on the move in the direction of Java and Sumatra were attacked by Ryujo's aircraft. The Japanese carrierborne warplanes also damaged the British light cruiser Durban, which had to break away toward Colombo in Ceylon. The Japanese continued their programme of incessant air attacks with carrierborne warplanes from Ryujo and land-based bombers. Two Allied tankers, a mercantile vessel and many smaller vessels were sunk, and another tanker and two transports severely damaged.

At 08.00 on 14 February air-raid sirens warned Palembang of the imminent arrival of a major Japanese attack. All available Allied air forces were at that time on missions to protect convoys at sea, and were not in reach of the local radio equipment. Firstly, a wave of Japanese bombers dropped its load on the 'P1' airfield, and then the accompanying fighters strafed the airfield.

While Allied warplanes attacked the vessels of the Western Force's invasion fleet on 13 February, Kawasaki Ki-56 'Thalia' transport aircraft of the 1^st Chutai, 2^nd Chutai and 3^rd Chutai of the Japanese army air force dropped paratroopers of the Teishin Shudan (Raiding Group), operating from the captured airfield of Kahang in Malay, over Pangkalan Benteng airfield. At the same time Mitsubishi Ki-21 'Sally' bombers of the 98^th Sentai dropped supplies to these paratroopers. The formation was escorted by a large force of Ki-43 fighters of the 59^th Sentai and 64^th Sentai of Lieutenant General Michio Sugawara’s 3^rd Air Division operating from bases in southern Malaya; Japanese carrierborne aircraft also supported the landed forces. As many as 260 men of the 2^nd Parachute Regiment, under the command of Colonel Seiichi Kume, dropped between Palembang and Pangkalan Benteng, and more than 100 other men came down to the west of the refineries at Pladjoe.

The Allied defence in this vital area was provided by a mere 150 British anti-aircraft gunners, 110 Dutch soldiers and 75 British ground troops at 'P1'. While the Japanese piled up vehicles to create road blocks, small firefights broke out with the defenders and some landed aircraft managed to refuel and take off for the undiscovered 'P2' airfield. The headquarters also moved to 'P2' after news arrived from the refinery and also from Palembang. In the afternoon the Allied and Japanese operations were deadlocked. The British still held the airfield, but they were short of ammunition and hindered by the Japanese blockade. After a false report of other Japanese parachute landings about 15.5 miles (25 km) away, the British commander decided to evacuate the airfield and the town. On the next day another 100 Japanese landed at the refinery. After a violent fight which continued the whole day, the defenders forced back the Japanese, but the refinery was heavily damaged by machine gun fire and set on fire. A number of other but smaller facilities in the same basic area were also damaged.

So, even though the Japanese paratroopers failed to capture the Pangkalan Benteng airfield, at the Pladjoe oil refinery they managed to gain possession of the entire complex before any major demolitions could be effected.

An improvised counterattack by Landstorm troops and anti-aircraft gunners from Praboemoelih managed to retake the complex, but suffered heavy losses. The planned demolition failed to do any serious damage to the refinery, but the oil stores were set ablaze. Two hours after first drop, another 60 Japanese paratroopers were dropped near Pangkalan Benteng airfield. On 14 February the surviving Japanese paratroopers advanced to the Musi, Salang and Telang rivers, near Palembang.

On the morning of 13 February a river boat commandeered by the Royal Navy as the Li Wo under the command of Lieutenant Thomas Wilkinson and used to ferry personnel and equipment between Singapore and the Netherlands East Indies, had meanwhile encountered the Japanese fleet. Although the Li Wo was armed with only one 4-in (102-mm) gun and two machine guns, its crew fired at the Japanese troop transport ships, setting one on fire and damaging several others, all while under fire from the Japanese cruisers. This action continued for 90 minutes until the Li Wo ran out of ammunition. Wilkinson then ordered the ramming of the nearest transport, before his ship was destroyed by Japanese fire.

The force encountered by Li Wo was Ozawa’s fleet operating to the north of Bangka as distant cover for the Japanese landings which took place shortly afterward. A vanguard went ashore on Bangka island off the north coast of Sumatra’s south-eastern half, while the main units landed closer to Palembang at the mouth of the Musi river and advanced on along the river to the town. No defence of the river’s mouth had been made by the Dutch as they believed that any such effort would be useless in the face of the overwhelmingly superior firepower which the Japanese warships would be able to deliver.

At this time Japanese reconnaissance aircraft spotted the local ABDA naval force, under the command of Rear Admiral Karel W. F. M. Doorman, on a northerly course at Gasperstrasse. On the instructions of General Sir Archibald Wavell, the ABDACOM commander-in-chief, Doorman had collected an ABDACOM naval force of five cruisers (the Dutch light cruisers De Ruyter, Java and Tromp, British heavy cruiser Exeter and Australian light cruiser Hobart) and 10 destroyers, to the south of Bali island and sortied on 14 February in the direction of Sumatra. Japanese fighter aircraft from Ryujo and other from land bases in Malaya attacked the ABDACOM force at 12.00 on the following day, and Doorman pulled all his ships back to the south.

The Japanese invasion fleet off the Bangka straight had also been spotted by British aerial reconnaissance from 'P2'. In the early morning a force of 22 Hurricane fighters, 35 Blenheim light bombers and three Hudson light bombers tried to attack the Japanese ships, and were engaged by Japanese fighters. At 'P2' the news of the Japanese paratrooper assault on 'P1' now became known, and the commander at 'P2' initiated the preparations for an evacuation of the airfield. Then news arrived that 'P1' had not yet been lost resulted in a short-term change of heart, and the returned aircraft were readied in the night for a new attack. In foggy conditions the Allied warplanes attacked the Japanese force, which had just begun its landing at the mouth of the Musi river. The Japanese air cover had to withdrew shortly after the start of the battle to refuel, so the Allies succeeded in getting direct hits on some of the transport vessels: Otawa Maru and 20 landing craft were sunk, and hundreds of Japanese troops were killed. The last Allied results achieved were by Hurricane fighters which strafed unprotected landing craft on the south-western beach of Bangka island.

Meanwhile the Dutch command had ordered the destruction of oil stocks and rubber dumps, and the immediate sinking of all the ferry vessels on the Musi river so they could not be seized and used by the Japanese. Also the defenders of P1 were to start a quick retreat. On the night of the 15^th of February Japanese units, which had survived the air raid at the Musi river’s mouth, reached Palembang and relieved the paratroopers landed at P1 and the refinery.

During the morning of 15 February, Wavell ordered a staged withdrawal of the ABDACOM forces toward an evacuation from Oosthaven, where there were several small ships, and these 12 ships were used on 17 February for the removal of about 2,500 British air force and 1,890 army personnel, 700 Dutch soldiers and about 1,000 civilians across the Sunda Strait to the island of Java; all the military personnel had to abandon their equipment. The Australian minesweeper Burnie covered the evacuation and also undertook the destruction of the harbour facilities and oil tanks. A small vessel remained in the harbour for a short time longer to evacuate any late-arriving refugees.

In the meantime the Japanese had completed their seizure of Palembang, and moved small numbers of troops up the river to Mengalla using smaller vessels.

All the Allied aircraft which were still airworthy were flown out to Java on 16 February, and the airfield personnel proceeded by sea to India. Once it had been learned that the Japanese had not immediately advanced to Oosthaven, a small Allied task force was landed there on 20 February to recover aircraft spares and demolish all the facilities which might otherwise have been of use to the Japanese once they did arrive.

On the 24 February the Japanese reached Gelumbang. On the previous day an anti-Dutch revolt, instigated by the Japanese, had broken out in the north-western half of Sumatra, and by the end of the following day the Japanese had secured most of the south-eastern half of Sumatra. Aircraft of the Japanese army and navy air forces started to operate from the bases in the south-eastern half of Sumatra to attack Allied positions in Java.

The Allied units remaining on Sumatra, most of them Dutch (the majority of the local units had deserted by this time), pulled back into the central and northern provinces of the island, from which the Dutch planned to retake the Palembang area and drive the Japanese from Sumatra. A concept little based on reality, this was frustrated by an aggressive Japanese pursuit from Palembang by a motorised reconnaissance force of about 750 men. The retreating forces under the command of Major C. F. Hazenberg numbered only about 350 Dutch regular troops in two companies. These were badly dispersed and could only fight delaying actions, which allowed the Japanese, who were better trained and better equipped, to advance swiftly. After three weeks, the Japanese were finally checked at Moearatebo on 2 March. Dutch reinforcements from Padangpandjang were able to move up when heavy rains made the rivers all but impassable to more Japanese troops, and the Japanese delay thus gave the Dutch commanders the time they required to deploy additional units from the central provinces and thereby prevent the retreating force’s flank from being turned.

Between 3 and 7 March there was small-scale but vicious fighting as Japanese units tried to cross the river. As the Japanese offensive ground to a halt, Dutch reconnaissance agents returned with reports that the Japanese had suffered many dead and wounded, and also that the regiment now numbered only about 200 men. Hazenberg therefore decided that the time was right for a counterattack on the night of 8/9 March. On 7 and 8 March local boats were secretly brought together and loaded with supplies and ammunition as the Dutch assault groups formed. On 8 March, however, there arrived news of the Dutch capitulation on Java, marking the success of the Japanese 'J' (ii), and all Dutch offensive efforts had to be ended as Sumatra was wholly dependent on the delivery of military supplies from Java, and it was decided to go over to the defensive on Sumatra. Western Sumatra had therefore to be left to the Japanese and only a small part of the island’s north would be held by the currently available forces for as long a time as possible, and certainly until an evacuation by sea could be organised.

The Dutch units destroyed all airfields and harbour facilities as they withdrew into defensive positions at the southern entrance of the Alice valley, where they planned to check the Japanese as long as possible. Should these positions fall, the remaining Dutch planned to undertake a campaign of guerrilla warfare. Yet this latter was almost impossible to plan and execute as the native population of Sumatra was in no way minded to co-operate with the Dutch colonial power, and many were prepared to betray the Dutch to the Japanese. The antipathy of the local population became abundantly clear when the Dutch wished to move about 3,000 Europeans and Christian civilians from refugee camps on the coast of Aceh province in the extreme north-west of the island, which in 1907 had been the last area to succumb to Dutch rule: a Moslem uprising which broke out shortly after the start of 'L' (i) prevented the effort.

The final phase of 'L' (i) began on 28 February, when 27 transport vessels departed Singapore with 22,000 men of Lieutenant General Takuma Nishimura’s Imperial Guards Division. The transport vessels were divided into four convoys protected by three cruisers, 10 destroyers, and a number of patrol boats and submarine chasers. by this time the Allies lacked any capability to intervene by air or sea, the convoys reached north-western Sumatra without interference.

On 12 March the 'Kobayashi' Detachment took Sabang island and the airfield at Koetaradja in 'T' (i) without meeting any opposition. The 'Yoshida' Detachment landed to the south of Idi with a single infantry battalion tasked with the seizure of the Lantja and Pangkalang Brandan oilfields before driving to the south in the direction of Medan and applying pressure on the Dutch positions there. The main force of the Imperial Guards Division landed about 4 miles (6.4 km) to the north-west of Tandjoengtiram with the task of advancing along the highway linking Pematang Siantar, Balige and Taroetoeng to cut off any Dutch forces attempting to withdraw from Medan and also to drive to the north with the object of taking Medan airfield there. The elements of the Imperial Guards Division later linked with a detachment of the 38^th Division moving up the island from Palembang. On 17 March troops of the 38^th Division entered Fort de Koch on the central part of the island’s south-west coast.

Sumatra fell on 28 March when Overakker surrendered 2,000 Dutch troops at Koetarjane, a mountain village 65 miles (105 km) to the north-west of Toba Meer. After this, the Japanese used many Allied prisoners of way to built a railway between Pekanbaru and Moera.