'Transom' was a British and US carrierborne air attack on Japanese targets at Soerabaja on the island of Java in the Japanese-occupied Netherlands East Indies (17/18 May 1944).

The attack on Soerabaja was the second and last joint British and US aircraft carrier raid in the Indian Ocean during 1944, and was undertaken to divert Japanese forces from the US 'Straightline' landing on Wakde island off New Guinea and make use of the US carrier Saratoga during her return voyage to the Pacific Ocean following her period of loan to the British. The warships involved in the operation sailed from Ceylon and refuelled in Western Australia before reaching the waters to the south of Java, where the carriers' aircraft were launched. On the morning of 17 May two groups of Allied aircraft made a co-ordinated and wholly unexpected attack on Soerabaja’s port and several industrial facilities. US heavy bombers struck Soerabaja that night and Australian aircraft laid mines in nearby waters. Both the US and Australian warplanes operated from bases in northern Australia.

Estimates of the damage inflicted by the Allies differ. Some sources describe the results as modest, and others contend that they were significant. The number of civilian casualties caused by the raid is unknown. There is consensus that the operation provided the Royal Navy with useful exposure to the US Navy’s superior carrier tactics. The attack had no effect on Japanese military deployments as the Eastern Fleet was not considered a serious threat.

Soerabaja is a city in the north-eastern part of Java that was part of the Netherlands East Indies at the time of World War II. It had become one of the main port cities of Asia during the later 19^th century and was the centre of the Netherlands East Indies' sugar export industry. Soerabaja’s economy entered a period of decline in the later part of the 1920s, but nonetheless remained an important commercial city.

Japanese forces invaded and conquered most of the Netherlands East Indies between December 1941 and March 1942, Java being the object of the 'J' operation. Soerabaja was bombed on many occasions during the campaign, the first air raid focusing on the city’s port and naval base, and the Dutch garrison surrendered on 8 March. Like the rest of Java, Soerabaja was administered by the Imperial Japanese army during the occupation of the Netherlands East Indies. Soerabaja remained an important naval base and industrial centre during the occupation. Japanese anti-submarine forces based at Soerabaja hunted Allied submarines operating in the Java Sea. The Wonokromo oil refinery located in the city was the only facility in Java that produced aviation fuel. Large numbers of Allied aircraft attacked Soerabaja on 22 July and the night of 8/9 November 1943. Smaller raids took place during most months from February 1944 until the end of the war in August 1945. Consolidated PBY Catalina flying boats of the Royal Australian Air Force also periodically dropped mines in the entrance to Soerabaja’s port from August 1943. From the start of 1944 minefields laid by aircraft considerably disrupted movements of shipping in and out of Soerabaja and sank several ships.

From the middle of 1942 until a time early in 1944, the Allies undertook no offensive naval operations in the Indian Ocean. Their main naval force there was Admiral Sir James Somerville’s small Eastern Fleet which, from January 1943, included no aircraft carriers, and its three elderly battleships were transferred elsewhere later in the year.The warships which remained to the fleet were capable only of protecting Allied shipping, but fortunately for the Allies the Japanese made no attempt at any large-scale operations in the Indian Ocean after the 'C' raid of the middle of 1942. This allowed the Eastern Fleet to focus on countering German and Japanese submarines and using its own submarines to raid Japanese shipping.

The plan adopted by the Allied leaders at the 'Sextant' conference of November 1943 in Cairo stated that ;the main effort against Japan should be made in the Pacific;, and that the Indian Ocean would be a subsidiary theatre. It was also decided that any offensive operations, including aircraft carrier raids, in the theatre would have the goals of ;maintaining pressure on the enemy, forcing dispersion of his forces, and attaining the maximum attrition of his air and naval forces and shipping'.

In January 1944 the Admiralty decided to undertake a major reinforcement of the Eastern Fleet as this was now feasible after by the surrender of the Italian navy in September 1943, which had removed one of the Royal Navy’s main opponents and given the Allies control over the Mediterranean Sea. A total of 146 warships was therefore scheduled to reach the Eastern Fleet over the next four months. These warships included three battleships, two aircraft carriers, 14 cruisers and large numbers of destroyers and other escort vessels. The first substantial group of reinforcements, which reached the Eastern Fleet’s base in Ceylon on 27 January, included the fleet carrier Illustrious, the battleships Queen Elizabeth and Valiant, and the battle-cruiser Renown. Many other ships arrived over the course of the year, but a continued shortage of destroyers hindered the fleet’s ability to undertake offensive operations until April, as priority was given to the escort of convoys.

Early in 1944 the Japanese military transferred its main naval attack force, the Combined Fleet, to Singapore. This resulted from the decision to shift the fleet from its bases in the central part of the Pacific Ocean, which had become vulnerable to US attack, and concentrate it at a location with good naval repair facilities and ready access to fuel. The Japanese did not intend to undertake large-scale attacks into the Indian Ocean but, not knowing this, Somerville believed that his force would be unable to counter the Combined Fleet should it enter the Indian Ocean, and more air units were despatched for the defence of Ceylon. The US Navy also agreed to the temporary transfer the fleet carrier Saratoga, escorted by three destroyers, from the Pacific to augment the Eastern Fleet.

Saratoga and her escorts joined the Eastern Fleet on 27 March. Illustrious and Saratoga, accompanied by much of the Eastern Fleet, undertook a successful carrierborne air raid against the Japanese-held island of Sabang in the Netherlands East Indies on 19 April as part of 'Cockpit': the Allied aircraft sank one ship, drove another aground, damaged oil storage tanks and destroyed up to 24 Japanese aircraft on the ground, while losing only one Allied aeroplane and driving off an attack by three Japanese aircraft.

Following 'Cockpit', Saratoga was directed to return to the USA for a refit. The chief of naval operations head of the US Navy, Admiral Ernest J. King, suggested to Admiral the Lord Louis Mountbatten, head of the South-East Asia Command, that Saratoga and vessels of the Eastern Fleet strike Soerabaja on her return voyage. King hoped that this would divert Japanese forces ahead of the US 'Straightline' assault on Wakde island scheduled for 17 May. Mountbatten agreed to the proposal.

Somerville decided to conduct the attack using almost the same forces as used in 'Cockpit'. One of the main differences was to substitute Grumman Avenger level and torpedo bombers for Illustrious's usual air wing of Fairey Barracuda torpedo and dive-bombers. This change was made because Soerabaja’s defences were expected to be stronger than those at Sabang, and Somerville had decided to launch the aircraft 180 miles (290 km) from the port city, which was beyond the Barracuda’s effective range. Because of the distance to be covered from Ceylon and the Royal Navy’s lack of experience in under-way replenishment, the final plan for 'Transom' involved the refuelling of the Eastern Fleet in the Exmouth Gulf of Western Australia before striking at Soerabaja The US Army Air Forces' 380^th Bombardment Group, which was based near Darwin in Australia, was to also bomb Soerabaja on the night after the carrier raid to prevent the Japanese from despatching aircraft to attack the Eastern Fleet as it withdrew. The Allies had good intelligence on the locations of Japanese facilities in Soerabaja, which aided the planning process. However, the Allies lacked information on the strength of Japanese air forces in the region, which forced the Eastern Fleet to assign large numbers of fighter aircraft to escort the strike force and protect the fleet rather than attacking ground targets.

The Eastern Fleet was organised into three forces for 'Transom'. Task Force 65 comprised Queen Elizabeth, Valiant and later Renown, the Free French battleship Richelieu, the light cruisers Newcastle, Nigeria and Free Dutch Tromp, and the destroyers Rotherham, Racehorse, Penn, Napier, Nepal, Quiberon, Quickmatch and Free Dutch Van Galen. Vice Admiral Sir Arthur Power’s TF66 comprised the carriers Illustrious and Saratoga under the command of Rear Admiral C. Moody, the light cruisers Ceylon and New Zealand Gambia, and the destroyers Quilliam, Quadrant, Queenborough and US Cummings, Dunlap and Fanning.

On 30 April the TF67 support force had departed Trincomalee with a number of Royal Fleet Auxiliary vessels in the form of Eagledale, Echodale, 8,296-ton Arndale, 5,892-ton Appleleaf, 5,911-ton Pearleaf and 5,150-ton Bacchus. TF67 was escorted by the heavy cruiser London, destroyers Rotherham and Dutch Van Galen, and frigate Findhorn. two cruisers and six destroyers. Somerville commanded the fleet from Queen Elizabeth. The warships were drawn from six navies, the capital ships being accompanied by three US destroyers, four British cruisers and three destroyers, four Australian destroyers, one Free Dutch cruiser and destroyer, and one New Zealand cruiser. The Australian light cruiser Adelaide also sailed from Fremantle in Western Australia to protect the tankers while they were at the Exmouth Gulf, and this allowed their two escorting cruisers to augment TF66 during the attack. Two squadrons of Supermarine Spitfire fighters were transferred from the RAAF’s No. 1 Wing at Darwin to the Exmouth Gulf to protect the Eastern Fleet while it refuelled, and Australian and US maritime patrol aircraft were assigned to operate offshore.

Each carrier operated an air group comprising units from their parent navies. Illustrious embarked two squadrons each of 14 Vought Corsair fighters and two squadrons each of nine Avenger bombers. Saratoga's air group comprised one squadron of 26 Grumman F6F Hellcat fighters, one squadron of 24 Douglas SBD Dauntless dive-bombers and one squadron of 18 Avenger bombers, as well as a single Hellcat allocated to the air group’s commander.

Soerabaja’s defences against air attack at the time of 'Transom' took the form of a few anti-aircraft guns, whose crews were inadequately trained. Radar stations and a network of observer posts were also sited to detect minelaying aircraft. The Japanese forces stationed in the city included the Imperial Japanese army’s 28^th Independent Mixed Brigade and the headquarters of the Imperial Japanese navy’s 2^nd Southern Expeditionary Fleet, the latter commanded by Vice Admiral Shiro Kawase.

TF67 was the first element of the Eastern Fleet to sail, departing on 30 April, while Forces 65 and 66 sailed on 6 May. The Allied ships proceeded to the Exmouth Gulf on a course that kept them at least 600 miles (965 km) from Japanese airfields in order to avoid detection and subsequent attack. The carriers' air wings practised the attack they would conduct on Soerabaja three times during the voyage. The warships arrived in the Exmouth Gulf on 14 and 15 May. While his ships were refuelling, Somerville met with Vice Admiral Thomas C. Kincaid, the commander of the US 7^th Fleet, Rear Admiral Ralph W. Christie, commander of the 7^th Fleet’s submarines, and Commodore Cuthbert Pope, the naval officer in charge at Fremantle, to discuss the most recent intelligence.

The Eastern Fleet departed the Exmouth Gulf on the afternoon of 15 May and proceeded to the north. It arrived at the flying off point at 06.30 on 17 May without being detected by the Japanese. One British and seven US submarines also took up positions near Soerabaja, in the southern entrance to the Strait of Malacca, and in the Bali, Lombok and Sunda Straits to support the Eastern Fleet. The submarines were positioned to rescue any Allied aircrew who were forced down, to attack ships that tried to escape from Soerabaja, and to intercept any Japanese warships that attempted to attack the Allied fleet.

The aircraft launched by the carriers were organised into two strike forces. Force A comprised nine Avenger machines from Illustrious, 12 Dauntless machines and an escort of eight Corsair machines: Force A’s Avenger aircraft were to bomb the Braat engineering works and the Dauntless aircraft the oil refinery. Force B was to bomb shipping and dock facilities in Soerabaja’s port, and comprised 21 Avenger and six Dauntless attack aircraft escorted by eight Corsair and 12 Hellcat fighters. The commander of Saratoga's air group, Commander Joseph C. Clifton, led both carriers' air wings during the attack. All of the aircraft had been launched and formed with the rest of their force by 07.20. Two of the British Avenger bombers crashed during take-off, their crews being rescued.

The attack on Soerabaja began at 08.30. The Japanese had not detected the aircraft as they approached, and were taken by total surprise. The two forces made a well-synchronised attack, Force A approaching Wonokromo from the south and Force B attacking the port from the north. No Japanese fighters were encountered, and the anti-aircraft guns were largely ineffective. One of Saratoga's Avenger aircraft was shot down, both members of its crew being taken prisoner.

The Allied pilots believed that they had inflicted heavy damage. They claimed to have damaged 10 ships, demolished both the Wonokromo oil refinery and the Braat engineering works, and destroyed 16 aircraft and several buildings at an airfield.

After the attack force had completed landing on the carriers at 10.50, the Eastern Fleet withdrew to the south-west in an attempt to obscure the fact that it was headed for the Exmouth Gulf. Somerville’s staff had not requested a debriefing from Clifton upon his return. As a result, they did not learn until photographs taken by one of Saratoga's photo-reconnaissance aircraft were dropped onto Queen Elizabeth at 15.00 that many worthwhile targets, including Japanese submarines, remained in Soerabaja’s port. Somerville later regretted not ordering a second strike during the afternoon of 17 May.

The eight submarines that supported 'Transom' were not actually need for the rescue of downed airmen, and none sank ships escaping from Soerabaja The US Rasher attacked a Japanese convoy near Ambon on 11 May while en route to take up station to the north of Soerabaja, sinking one ship and damaging several others. The US Angler sank a cargo ship in the Sunda Strait on 20 May but was counterattacked by the warships escorting it. The submarine had to abort its patrol on the following day after its crew fell sick as a result either of contaminated drinking water or of fumes from cleaning chemicals.

The heavy bomber raid on Soerabaja to cover the Eastern Fleet’s withdrawal took place on the night of 17/18 May. Seven Consolidated B-24 Liberator four-engined bombers were despatched from Darwin and refuelled at Corunna Downs airfield in Western Australia before proceeding to Soerabaja and attacking its port with demolition bombs, which caused further fires and damage. RAAF Catalina flying boats flying from Yampi Sound in Western Australia also laid mines near the city during May to support the landing at Wakde. A minelaying mission by Catalina machines of Nos 11 and 43 Squadrons on the night of 20/21 May encountered heavy opposition from the Japanese defenders, who were still on high alert following the carrier and heavy bomber raids, and one of the Australian aircraft was destroyed.

Saratoga and her three escorting destroyers detached from the Eastern Fleet shortly before sunset on 18 May, and steamed to Fremantle. The rest of the Eastern Fleet reached the Exmouth Gulf during the morning of the following day, refuelled and sailed for Ceylon before sunset. Adelaide and one of the Australian destroyers which had been attached to the Eastern Fleet left the Exmouth Gulf bound for Fremantle after the tanker group departed on 19 May. The Eastern Fleet arrived back at Ceylon on 27 May. Saratoga reached Bremerton on the west coast of the USA on 10 June and after a refit rejoined the Pacific Fleet in September 1944.

As had been the case with 'Cockpit' and the several other carrierborne raids the Eastern Fleet conducted in 1944, 'Transom' exercised no effect on Japanese deployments. This was because the Combined Fleet did not regard the Eastern Fleet as a threat, and was under orders to preserve its strength to contest a major US offensive expected in the central Pacific. The Japanese leadership incorrectly interpreted the US 'Horlicks' landing on Biak island off the northern coast of New Guinea on 27 May as being the main Allied effort, and the Combined Fleetdespatched a powerful force to make a counterattack on 10 June in 'Kon'. This was cancelled two days later when it became apparent that the Americans were about to invade the Mariana islands group in the central Pacific, and the Combined Fleet's 'A' operation was defeated during the Battle of the Philippine Sea on 19/20 June.