'Boomerang' (ii) was a US air attack by Major General Curtis E. LeMay’s XX Bomber Command of General Henry H. Arnold’s 20th AAF from a forward base at Trincomalee in Ceylon against the Japanese-operated oilfields and their associated installations near Palembang at the south-eastern end of Sumatra in the Japanese-occupied Netherlands East Indies, and also against the waters off Penang, Singapore, Saigon, Cam Ranh Bay, Pakchan and the estuary of the Yangtze river (28 August 1944).
In the course of 162 sorties, the American bombers laid 987 mines, and air/sea rescue cover and general support off Japanese-occupied Malaya and Netherlands East Indies was provided by Admiral Sir James Somerville’s Eastern Fleet, which currently comprised the battleships Howe, Queen Elizabeth and French Richelieu, the battle-cruiser Renown, the fleet carriers Illustrious, Indomitable and Victorious, 11 cruisers including Ceylon and Kenya, and 32 destroyers including Racehorse, Rapid, Relentless, Rocket and Rotherham.
After its 'L' conquest of the island during February and March 1942, the Imperial Japanese army controlled the Royal Dutch Shell company’s oil refineries on Sumatra, these including Pangkalan Brandan and Pladjoe (Pladju), as well as the Standard-Vacuum Oil Company (Stanvac) refinery at Sungei (Soengai) Gerong. The oil refined at the small Pangkalan Brandan refinery in northern Sumatra was transported to port facilities at nearby Pangkalan Susu for shipment directly to Singapore and other locations in the Malayan area.
Oil production was centred at Prabumulih, some 43.5 miles (70 km) from Palembang in the south-eastern part of Sumatra. From this crude oil was piped to the large Pladjoe refinery, a few miles to the north of Palembang. It was in February 1942 that the Japanese 2nd Parachute Regiment captured Pladjoe before it could be destroyed, and the Japanese later named Pladjoe, which was managed by Nihon Sekiyu, as the 'No. 1 Refinery'. This facility was able to refine 45,000 barrels per day and its speciality was high-octane aviation fuel production. In the period before World War II, Stanvac also operated several oilfields and transported the crude oil to its Sungei Gerong refinery, to the east of Palembang. After they had captured Sungei Gerong, they named it the 'No. 2 Refinery', and under the management of Mitsubishi Sekiyu this too was capable of refining 45, 000 barrels per day. These two refineries, which were the largest in South-East Asia, had a combined annual capacity of 20.46 million barrels, and were capable of producing 78% of Japan’s aviation fuel and 22% of its fuel oil requirements.
The Imperial Japanese army used captured British and Dutch tankers, most of them comparatively small, to transport fuel across the Musi (Moesi) river, which joins the Ogan and Komering rivers near Palembang. Below Palembang, the Musi is deep enough for ocean-going vessels and about 50 miles (80 km) to the north it enters the waters of the Bangka Strait. Japan’s wartime demands for fuel were so great that almost daily trips were needed to transport the oil from Sumatra to Singapore for further shipment to other parts of the Japanese empire. Fuel also was transported either in bulk or by case (tins) to the smaller more remote locations in and around Malaya and the former Dutch East Indies.
Asiatic Petroleum, a subsidiary of Royal Dutch Shell Oil, formerly owned storage facilities at Pulau Bukum and Pulau Sebarok near Singapore, and petroleum products were delivered by sea from Sumatra and stored in these captured centres. Round trips from Palembang to Singapore and back, including loading and discharging fuel, averaged about one week, but many trips took longer, indicating possible loading and unloading difficulties and/or the ships' engine problems and perhaps groundings.
Their very remoteness in Sumatra permitted the operation these oil facilities by the Japanese with impunity from Allied attack until the Allied meeting at the 'Sextant' conference at Cairo in Egypt during November 1943. Attended by President Franklin D. Roosevelt, Prime Minister Winston Churchill, Generalissimo Chiang Kai-shek and the British and US Combined Chiefs-of-Staff, the conference was intended to address future military operations against Japan, and one of the agreements reached was for the bombing of vital targets in the Dutch East Indies during 1944.
This it was within this context that on the night of 10/11 August 1944 the USAAF undertook 'Boomerang' (ii). Some 54 Boeing B-29 Superfortress bombers of the XX Bomber Command’s 58th (Very Heavy) Bombardment Wing, commanded by Brigadier General LaVern G. Saunders, lifted off from their base at Chengtu in China, staged through the newly completed 7,200-ft (2195-m) runway at RAF China Bay, near Trincomalee in Ceylon, to make a radar-guided night attack on the Pladjoe refinery. The bombers flew individually from China Bay straight to Siberoet island, off Pandang in southern Sumatra, and then directly to Palembang. About 12 of the bombers failed to attack for varied reasons, but 39 aircraft reached their primary targets, two bombed the secondary target of Pangkalan Brandan refinery, one bombed the airfield at Djambi and eight mined the Musi river along which all of Palembang’s product was shipped. Just nine aircraft of Colonel Alva D. Harvey’s 444th Bomb Group reached Palembang and attacked through heavy overcast with 36 500-lb (227-kg) HE bombs and 16 photo-flash bombs. The results at Pladjoe were unobserved, but later deemed poor, and as a result no other B-29 raids were staged through Ceylon.
The eight B-29 minelaying aircraft of Colonel Alan D. Clark’s 462nd Bomb Group had greater success. Descending 500 ft (150 m) below the 1,00-ft (305-m) ceiling, the bombers strafed Japanese ships on the Musi river and dropped 16 mines in the first such operation by the B-29. The aircraft claimed three ships sunk, two others damaged and a one-month closure of the river approach to the refinery.
The 3,855-mile (6205-km) flight of 19 hours 40 minutes from Ceylon to Palembang and the parallel 4,030-mile (6485-km) flight to the Musi river and back, were the longest single-stage missions flown by USAAF combat aircraft in World War II.
Somerville’s Eastern Fleet organised and implemented a complex air/sea rescue undertaking in support of 'Boomerang' (ii), the ships involved including the light cruiser Ceylon, destroyer Redoubt, submarines Terrapin and Trenchant, a number of smaller vessels and an assortment of aircraft types. The submarines, based at Trincomalee, patrolled to the west of Sumatra and acted as radio beacons.
One B-29 was lost on its return flight as a result of fuel exhaustion, and went down into the sea some 90 miles (145 km) off China Bay. British aircraft and Redoubt homed on a signal from the B-29’s life raft. One gunner had been killed in the ditching, but the other crewmen were picked up. This was the only B-29 lost in the raid.
In conjunction with the long-distance raid on Palembang and to maximise psychological impact of long-range bombing on Japan’s leaders, on the same night other aircraft of the 444th Bomb Group flew a 3,120-mile (5020-km) raid on the Japanese port city of Nagasaki, which the aircraft bombed from an altitude of 18,000 ft (5485 m). Seven of the bombers are credited with hitting their primary target.
On 5 November 1944 the XX Bomber Command launched 76 B-29 bombers from Kharagpur, to the west of the Indian city of Calcutta, on the first USAAF attack on Singapore. Each of the aircraft was armed with just two 1,000-lb (454-kg) bombs as a result of the great distance to Singapore. The primary target was the former British 'King George VI' graving dock and the secondary target was the refinery at Pangkalan Brandan. Some 53 of the bombers attacked Singapore and seven attacked Pangkalan Brandan.