View source for Operation Transom

{{Short description|1944 British-American air raid on Surabaya}}
{{Featured article}}
{{Use dmy dates|date=July 2020}}
{{Infobox military conflict
| conflict    = Operation Transom
| partof      = the [[South-East Asian theatre of World War II]]
| image       = Carrier strike on Surabaya, Java in May 1944.jpg
| caption     = [[Surabaya]] during the attack by Allied carrier aircraft on 17 May 1944
| image_size  = 300px
| alt         = Black and white aerial photograph of a harbour with smoke rising from several locations
| date        = 17 May 1944
| place       = [[Surabaya]], [[Netherlands East Indies]]
| result      = Allied victory
| coordinates             = {{Coord|7.211035|S|112.730260|E|display=inline, title}}
| map_type    = Indonesia Java
| map_relief  = yes
| map_size    = 300
| map_caption = Location of Surabaya in Java
| combatant1  = {{flag|United Kingdom}}<br>{{flag|United States|1912}}<br>{{flag|Australia}}<br />{{flagcountry|Provisional Government of the French Republic}}<br />{{flagcountry|Dutch government-in-exile}}<br>{{flagcountry|Dominion of New Zealand}}
| combatant2  = {{flagcountry|Empire of Japan}}
| commander1  = {{flagicon|United Kingdom}} [[James Somerville]]
| commander2  = Unknown
| strength1   = 76 aircraft<br>2 aircraft carriers<br>3 battleships<br>1 battlecruiser<br>6 cruisers<br>14 destroyers<br>8 submarines
| strength2   = Anti-aircraft batteries
| casualties1 = 3 aircraft destroyed
| casualties2 = Accounts differ
| casualties3 = Unknown civilian casualties
| notes       =
| campaignbox = {{Campaignbox Bombing of SE Asia 1944-45}}
}}
'''Operation Transom''' was an attack by [[Allies of World War II|Allied]] forces against the Japanese-occupied city of [[Surabaya]] on the Indonesian island of [[Java]] during [[World War II]]. Conducted by the British-led [[Eastern Fleet]], the operation took place on 17 May 1944 and involved American and British [[carrier-based aircraft]] bombing the city's docks and an [[oil refinery]]. An American [[torpedo bomber]] was shot down, and two British torpedo bombers were lost in accidents.

The attack on Surabaya was the second, and final, joint American-British [[aircraft carrier]] raid in the Indian Ocean during 1944. It was undertaken to divert Japanese forces from the [[Battle of Wakde|Allied landing on Wakde island]] off [[New Guinea]] and make use of the American aircraft carrier on its return voyage to the Pacific. The warships involved in the operation sailed from [[Ceylon]] and refuelled in [[Western Australia]] before reaching the waters south of Java, where the carriers' aircraft were launched. On the morning of 17 May two groups of Allied aircraft made a coordinated attack on Surabaya's port and several industrial facilities that took the Japanese by surprise. American [[heavy bomber]]s struck Surabaya that night and Australian aircraft laid [[Naval mine|mines]] in nearby waters; these aircraft 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 British [[Royal Navy]] with useful exposure to superior [[United States Navy]] carrier tactics. The attack had no effect on Japanese military deployments as the Eastern Fleet was not considered a serious threat.

==Background==
{{seealso|Indian Ocean in World War II}}
===Surabaya in World War II===
[[Surabaya]] is a city in eastern [[Java]] that was part of the [[Netherlands East Indies]] (NEI) at the time of World War II. It became one of the main port cities in Asia during the late 19th century and was the centre of the NEI's [[Sugar industry|sugar export industry]]. Surabaya's economy began to decline in the 1920s, but it remained an important commercial city.{{sfn|Dick|2003|pp=xvii–xviii}}

Japanese forces [[Dutch East Indies campaign|invaded and conquered]] most of the NEI between December 1941 and March 1942.{{sfn|Dear|Foot|2001|p=613}} Surabaya was bombed on many occasions during the campaign, the first air raid focusing on the city's port and naval base.{{sfn|Dick|2003|p=74}} The Dutch garrison surrendered on 8 March.{{sfn|Dick|2003|p=75}} Like the rest of Java, Surabaya was administered by the [[Imperial Japanese Army]] during the [[Japanese occupation of the Dutch East Indies|occupation of the Netherlands East Indies]].{{sfn|Dear|Foot|2001|p=613}}{{sfn|Dick|2003|p=76}}

Surabaya remained an important naval base and industrial centre during the occupation. Japanese [[anti-submarine warfare|anti-submarine]] forces based at Surabaya hunted Allied [[submarine]]s operating in the [[Java Sea]].{{sfn|Hobbs|2011|p=42}} The [[Wonokromo]] oil refinery located in the city was the only facility in Java that produced [[Avgas|aviation fuel]].{{sfn|Hobbs|2011|p=42}}{{sfn|Roskill|1960|p=357}} Large numbers of Allied aircraft attacked Surabaya on 22 July and the night of 8/9 November 1943. Areas across the city were bombed during the first of these raids. Small raids took place during most months from February 1944 until the end of the war in August 1945.{{sfn|Dick|2003|pp=78–79}} [[Royal Australian Air Force]] [[Consolidated PBY Catalina]] aircraft also periodically dropped [[naval mine]]s in the entrance to Surabaya's port from August 1943. From the start of 1944 minefields laid by aircraft considerably disrupted movements of shipping in and out of Surabaya and sank several ships.{{sfn|Odgers|1968|pp=359, 363}}

===Allied and Japanese plans===
From mid-1942 until early 1944 the Allies did not undertake any offensive naval operations in the [[Indian Ocean]]. Their main naval force there was the small British-led [[Eastern Fleet]] which was commanded by Admiral [[James Somerville|Sir James Somerville]]. From January 1943 the fleet did not include any [[aircraft carrier]]s and its three elderly [[battleship]]s were transferred elsewhere later in the year.{{sfn|Mawdsley|2019|pp=407–408}} The remaining ships were capable only of protecting Allied shipping.{{sfn|Roskill|1960|p=347}} Fortunately for the Allies, the Japanese did not attempt any large-scale operations in the Indian Ocean after mid-1942. This allowed the Eastern Fleet to focus on countering German and Japanese submarines and using its own submarines to raid Japanese shipping.{{sfn|Mawdsley|2019|p=408}}
[[File:Admiral James Somerville visiting USS Saratoga on 3 April 1944.jpg|thumb|left|alt=Black and white photo of men in military uniforms on the deck of an aircraft carrier|Admiral [[James Somerville]] addressing the crew of {{USS|Saratoga|CV-3|6}} on 3 April 1944]]

The plan adopted by the [[Allies of World War II|Allied]] leaders at the November 1943 [[Cairo Conference]] 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".{{sfn|Roskill|1960|p=346}}

In January 1944 the [[British Admiralty|Admiralty]], the British government institution responsible for administering the [[Royal Navy]], decided to substantially reinforce the Eastern Fleet.{{sfn|Roskill|1960|p=347}} This had been made possible by the surrender of the [[Regia Marina|Italian Navy]] in 1943, which removed one of the Royal Navy's main opponents and gave the Allies control over the [[Mediterranean Sea]].{{sfn|Mawdsley|2019|p=409}} A total of 146 warships were scheduled to arrive over the next four months. These included three battleships, two aircraft carriers, fourteen [[cruiser]]s and large numbers of [[destroyer]]s and other escort vessels. The first substantial group of reinforcements reached the Eastern Fleet's base at [[Ceylon]] on 27 January; these included the aircraft carrier {{HMS|Illustrious|87|6}}, battleships {{HMS|Queen Elizabeth|1913|6}} and {{HMS|Valiant|1914|2}} and [[battlecruiser]] {{HMS|Renown|1916|6}}.{{sfn|Roskill|1960|p=347}} Many other ships arrived over the course of the year.{{sfn|Roskill|1960|p=347}} Shortages of destroyers hindered the fleet's ability to conduct offensive operations until April, as priority was given to escorting convoys.{{sfn|Winton|1993|p=176}}

In early 1944 the Japanese military transferred its main naval striking force, the [[Combined Fleet]], to [[Singapore]]. This change was made to evacuate the fleet from its bases in the central Pacific, which had become vulnerable to American attacks, and concentrate it at a location with good naval repair facilities and ready access to fuel. The Japanese did not intend to undertake any large-scale attacks into the Indian Ocean. Somerville believed that his force would be unable to counter the Combined Fleet if it entered the Indian Ocean, and more air units were dispatched to protect Ceylon.{{sfn|Roskill|1960|pp=347–348}} The [[United States Navy]] also agreed to temporarily transfer the aircraft carrier {{USS|Saratoga|CV-3|6}} and three destroyers from the Pacific to augment the Eastern Fleet.{{sfn|Roskill|1960|p=348}}

''Saratoga'' and her escorts [[Operation Diplomat|joined the Eastern Fleet]] on 27 March 1944.{{sfn|Roskill|1960|p=354}} ''Illustrious'' and ''Saratoga'', accompanied by much of the Eastern Fleet, conducted a successful air raid against the Japanese-held island of [[Weh Island|Sabang]] in the NEI on 19 April as part of [[Operation Cockpit]].{{sfn|Kirby|1962|pp=380–381}} The Allied aircraft sank one ship, drove another [[Ship grounding|aground]], damaged oil storage tanks and destroyed up to 24 Japanese aircraft on the ground.{{sfn|Roskill|1960|p=356}} One Allied aircraft was shot down, and an attack on the fleet by three Japanese aircraft was defeated.{{sfn|Brown|2009|p=80}}

==Prelude==
[[File:1944-05-15JapWW2BattlefrontAtlas.jpg|thumb|upright=1.3|alt=Map of the western Pacific Ocean and South East Asia marked with the territory controlled by the Allies and Japanese as at mid-May 1944|The strategic situation in the Pacific in mid-May 1944. The red shaded area was controlled by the Allies and the remainder was controlled by Japan.]]
Following Operation Cockpit, ''Saratoga'' was directed to return to the United States for a [[refit]].{{sfn|Roskill|1960|p=356}} The head of the US Navy, Admiral [[Ernest King]], suggested to Admiral [[Louis Mountbatten, 1st Earl Mountbatten of Burma|Lord Louis Mountbatten]], the commander of [[South East Asia Command]], that the carrier and other vessels of the Eastern Fleet strike Surabaya on her return voyage. King hoped that this would divert Japanese forces ahead of the Allied [[Battle of Wakde|landing at Wakde island]] off New Guinea that was scheduled for 17 May. Mountbatten agreed to the proposal.{{sfn|Gill|1968|p=416}}

Somerville decided to conduct the attack using almost the same forces as had been involved in Operation Cockpit.{{sfn|Roskill|1960|p=356}} One of the main differences was to substitute [[Grumman Avenger]]s for ''Illustrious''{{'}}s usual air wing of [[Fairey Barracuda]] torpedo and [[dive bomber]]s. This change was made because Surabaya's defences were expected to be stronger than those at Sabang, and Somerville had decided to launch the aircraft {{convert|180|mi|km}} from the city, which was beyond the Barracudas' effective range.{{sfn|Roskill|1960|pp=356–357}} Because of the distance to be covered from Ceylon and the Royal Navy's lack of experience in [[underway replenishment]], the final plans for the operation involved the Eastern Fleet refuelling at [[Exmouth Gulf]] in [[Western Australia]] before striking Surabaya.{{sfn|Hobbs|2011|p=42}} The [[United States Army Air Forces|United States Army Air Forces']] [[380th Air Expeditionary Wing|380th Bombardment Group]], which was based near [[Darwin, Northern Territory|Darwin]] in Australia, was to also bomb Surabaya on the night after the carrier raid to prevent the Japanese from dispatching aircraft to attack the Eastern Fleet as it withdrew.{{sfn|Odgers|1968|p=229}} The Allies had good intelligence on the locations of Japanese facilities in Surabaya, which aided planning for air raids on the city.{{sfn|Dick|2003|p=79}} They 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.{{sfn|Hobbs|2011|p=46}}

The Eastern Fleet was organised into three forces for Operation Transom. Force 65 comprised ''Queen Elizabeth'', ''Valiant'', ''Renown'', the French battleship [[French battleship Richelieu|''Richelieu'']], two cruisers and eight destroyers. Force 66 was made up of ''Illustrious'', ''Saratoga'', two cruisers and six destroyers. Force 67 was the replenishment group and comprised six [[Tanker (ship)|tankers]], a [[distilling ship|water distilling ship]] and two cruisers. Somerville commanded the fleet from ''Queen Elizabeth''.{{sfn|Gill|1968|pp=416–417}} The warships were drawn from six navies, the [[capital ship]]s being accompanied by three American destroyers, four British cruisers and three destroyers, four Australian destroyers, a Dutch cruiser and destroyer and a New Zealand cruiser.{{sfn|Faulkner|2012|p=224}} The Australian light cruiser {{HMAS|Adelaide|1918|6}} also sailed from [[Fremantle]] in Western Australia to protect the tankers while they were at Exmouth Gulf; this allowed their two escorting cruisers to augment Force 66 during the attack.{{sfn|Gill|1968|p=417}} Two squadrons of [[Supermarine Spitfire]] fighters were transferred from [[No. 1 Wing RAAF]] at Darwin to Exmouth Gulf to protect the Eastern Fleet while it refuelled and Australian and American [[maritime patrol aircraft]] were assigned to operate offshore.{{sfn|Odgers|1968|p=229}}

Each carrier had an [[Carrier air wing|air group]] made up of units from their parent navies. ''Illustrious'' embarked two squadrons equipped with 14 [[Vought F4U Corsair]] [[fighter aircraft|fighters]] each and two squadrons with nine Avengers. ''Saratoga''{{'}}s air group comprised a squadron with 26 [[Grumman F6F Hellcat]] fighters, a squadron with 24 [[Douglas SBD Dauntless]] dive bombers and a squadron operating 18 Avenger torpedo bombers, as well as a single Hellcat allocated to the Air Group Leader.{{sfn|Brown|2009|p=83}}

Surabaya's defences against air attack at the time of Operation Transom included a few [[Anti-aircraft warfare|anti-aircraft guns]], whose crews were inadequately trained.{{sfn|Hobbs|2011|p=45}} [[Radar]] stations and a network of observer posts were also sited to detect minelaying aircraft.{{sfn|Odgers|1968|p=363}} The Japanese forces stationed in the city included the Imperial Japanese Army's [[28th Independent Mixed Brigade]] and the headquarters of the [[Imperial Japanese Navy|Imperial Japanese Navy's]] [[Southern Expeditionary Fleet (Imperial Japanese Navy)|2nd Southern Expeditionary Fleet]].{{sfn|Fuller|1992|pp=119, 286}}

==Attack==
[[File:Avenger being armed on HMS Illustrious (87) 1944.jpg|thumb|alt=Black and white photograph of an aircraft being loaded with bombs|An Avenger being loaded with bombs on board {{HMS|Illustrious|87|6}} before the raid on Surabaya]]
Force 67 was the first element of the Eastern Fleet to sail, departing on 30 April. Forces 65 and 66 sailed on 6 May. The Allied ships proceeded to Exmouth Gulf on a course that kept them at least {{convert|600|mi|km}} from Japanese airfields to avoid being detected or attacked.{{sfn|Gill|1968|p=417}} The carriers' air wings practised the attack they would conduct on Surabaya three times during the voyage.{{sfn|Hobbs|2011|p=42}} The warships arrived at Exmouth Gulf on 14 and 15 May. While his ships were refuelling, Somerville met with the commander of the [[United States Seventh Fleet]], Vice Admiral [[Thomas C. Kinkaid]], Rear Admiral [[Ralph Waldo Christie]] who commanded the fleet's submarines, and the Naval Officer In Charge Fremantle, Commodore [[Cuthbert Pope]], to discuss the most recent intelligence.{{sfn|Gill|1968|p=417}}

The Eastern Fleet departed Exmouth Gulf on the afternoon of 15 May and proceeded north. It arrived at the flying off point at 6:30&nbsp;am local time on 17 May without being detected by the Japanese.{{sfn|Roskill|1960|p=357}} One British and seven American submarines also took up positions near Surabaya, the southern entrance to the [[Strait of Malacca]] and the [[Bali Strait|Bali]], [[Lombok Strait|Lombok]] and [[Sunda Strait]]s to support the Eastern Fleet.{{sfn|Gill|1968|p=419}}{{sfn|Hobbs|2011|p=41}} The submarines were positioned to rescue Allied aircrew that were forced down, attack ships that tried to escape from Surabaya and intercept any Japanese warships that attempted to attack the Allied fleet.{{sfn|Blair|2001|p=629}}

The aircraft launched by the carriers were organised into two strike forces. Force A was made up of nine Avengers from ''Illustrious'', twelve Dauntless dive bombers and an escort of eight Corsairs. Force A's Avengers were to bomb the Braat Engineering Works and the Dauntlesses the oil refinery.{{sfn|Hobbs|2011|p=45}} Force B was to attack shipping and dock facilities in Surabaya's port. It comprised twenty-one Avengers and six Dauntlesses escorted by eight Corsairs and twelve Hellcats.{{sfn|Hobbs|2011|pp=42, 45}} The commander of ''Saratoga''{{'}}s air group, Commander [[Joseph C. Clifton]], led both carriers' air wings during the attack.<ref name="NYT Clifton obit">{{cite news |title=Joseph C. Clifton, Admiral, 59, dies |url=https://timesmachine.nytimes.com/timesmachine/1967/12/26/88500593.html?pageNumber=33 |access-date=24 May 2021 |work=The New York Times |date=26 December 1967}}</ref><ref>{{cite web |title=Joseph C. Clifton |url=https://valor.militarytimes.com/hero/311017 |website=The Hall of Valor Project |publisher=Sightline Media Group |access-date=24 May 2021}}</ref> All of the aircraft were launched and formed up with the rest of their force by 7:20&nbsp;am.{{sfn|Roskill|1960|p=357}} Two British Avengers crashed during takeoff, their crews being rescued.{{sfn|Evans|Grossnick|2015|p=196}}
[[File:Surabaya under attack during Operation Transom.jpg|thumb|left|alt=Black and white aerial photograph of a city and port area with explosions taking place|An airfield and port installations under attack during the raid]]

The attack on Surabaya commenced at 8:30&nbsp;am. The Japanese had not detected the aircraft as they approached, and were taken by surprise.{{sfn|Roskill|1960|p=357}} 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 fighter aircraft were encountered, and the anti-aircraft guns were largely ineffective.{{sfn|Hobbs|2011|p=45}} One of ''Saratoga''{{'}}s Avengers was shot down, and both members of its crew became [[prisoners of war]].{{sfn|Evans|Grossnick|2015|p=196}}

The Allied pilots believed that they had inflicted heavy damage.{{sfn|Roskill|1960|p=357}} They claimed to have damaged ten ships, demolished both the Wonokromo oil refinery and the Braat Engineering Works and destroyed 16 aircraft and several buildings at an airfield.{{sfn|Gill|1968|p=418}}

After the strike force completed landing on the carriers at 10:50&nbsp;am, the Eastern Fleet withdrew to the south-west in an attempt to obscure the fact that it was headed for Exmouth Gulf.{{sfn|Hobbs|2011|p=45}}{{sfn|Gill|1968|p=419}} 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 3:00&nbsp;pm that many worthwhile targets, including Japanese submarines, remained in Surabaya's port. Somerville later regretted not ordering a second strike during the afternoon of 17 May.{{sfn|Hobbs|2011|p=45}}{{sfn|Roskill|1960|pp=357–358}}

The eight submarines that supported Operation Transom were not needed to rescue downed airmen, and none sank ships that were escaping from Surabaya.{{sfn|Blair|2001|p=629}} {{USS|Rasher}} attacked a Japanese [[convoy]] near [[Ambon Island|Ambon]] on 11 May while en route to take up station north of Surabaya, sinking one ship and damaging several others.{{sfn|Blair|2001|p=632}} {{USS|Angler|SS-240|6}} sank a cargo ship in Sunda Strait on 20 May but was counter-attacked by the ships escorting it. The submarine had to abort its patrol the next day after the crew became sick due to either contaminated drinking water or fumes from cleaning chemicals.{{sfn|Blair|2001|pp=630–631}}<ref>{{cite web |title=Angler (SS-240) |url=https://www.history.navy.mil/research/histories/ship-histories/danfs/a/angler.html |website=Dictionary of American Naval Fighting Ships |publisher=Naval History and Heritage Command|access-date=26 June 2021}}</ref> The historian [[Clay Blair]] judged that the submarines would have likely achieved more if they had undertaken routine patrols or been stationed near the major Japanese naval anchorage at [[Tawi-Tawi]].{{sfn|Blair|2001|p=629}}

The heavy bomber raid against Surabaya that had been planned to cover the Eastern Fleet's withdrawal took place on the night of 17/18 May. Seven [[Consolidated B-24 Liberator]]s were dispatched from Darwin and refuelled at [[Corunna Downs Airfield]] in Western Australia. They then proceeded to Surabaya and attacked its port with demolition bombs. This caused further fires and damage.{{sfn|Odgers|1968|p=230}} RAAF Catalinas flying from [[Yampi Sound]] in Western Australia also laid mines near the city during May to support the landing at Wakde.{{sfn|Odgers|1968|pp=227, 364}} A minelaying mission conducted by Catalinas from [[No. 11 Squadron RAAF|Nos. 11]] and [[No. 43 Squadron RAAF|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. One of the Australian aircraft was destroyed.{{sfn|Odgers|1968|p=230}}

==Aftermath==
[[File:USS Saratoga viewed from HMS Illustrious at the conclusion of Operation Transom.jpg|thumb|alt=Black and white photo of men standing on the deck of a ship looking at another ship which is sailing nearby|''Illustrious''{{'}}s crew farewelling ''Saratoga'' on 18 May 1944]]
===Subsequent operations===
''Saratoga'' and her three escorting American destroyers detached from the Eastern Fleet shortly before sunset on 18 May, and proceeded to Fremantle. The remainder of the Eastern Fleet reached Exmouth Gulf the next morning, and sailed for Ceylon before sunset after refuelling again. ''Adelaide'' and one of the Australian destroyers that had been attached to the Eastern Fleet left Exmouth Gulf bound for Fremantle after the tanker group departed on 19 May.{{sfn|Gill|1968|p=419}} The Eastern Fleet arrived back at Ceylon on 27 May.{{sfn|Faulkner|2012|p=224}} ''Saratoga'' reached [[Bremerton, Washington]], on 10 June and after a refit re-joined the [[United States Pacific Fleet|Pacific Fleet]] in September 1944.{{sfn|Brown|2009|p=81}}<ref>{{cite web |title=Saratoga V (CV-3) |url=https://www.history.navy.mil/research/histories/ship-histories/danfs/s/saratoga-v.html |website=Dictionary of American Naval Fighting Ships |publisher=Naval History and Heritage Command |access-date=25 July 2021}}</ref>

As was also the case with Operation Cockpit and the several other carrier raids the Eastern Fleet conducted in 1944, Operation Transom did not have any effect on Japanese deployments.{{sfn|Kirby|1962|p=384}}{{sfn|Faulkner|2012|p=221}} 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 American offensive that was expected to take place in the central Pacific.{{sfn|Roskill|1960|p=355}} The Japanese leadership incorrectly interpreted the American landing at [[Biak]] off the north coast of New Guinea on 27 May as being the main Allied effort, and the Combined Fleet dispatched a powerful force to make a counter attack on 10 June in what was designated [[Operation Kon]]. This attack was cancelled two days later when it became apparent that the Americans were about to invade the [[Mariana Islands]] in the Central Pacific, and the Combined Fleet was defeated during the [[Battle of the Philippine Sea]] fought between 19 and 20 June.{{sfn|Mawdsley|2019|pp=249–250, 398–406}}

===Assessments===
Accounts of the damage inflicted during Operation Transom differ. [[Stephen Roskill]], the official historian of the Royal Navy's role in World War II, wrote in 1960 that although the Allies believed during the war that "many of the ships in harbour had been sunk or damaged and&nbsp;...&nbsp;severe destruction had been done to the oil refinery and naval base", Japanese records "do not confirm that either their shipping or the shore facilities suffered at all heavily". These records indicated that only a single small ship was sunk. Roskill judged that "fires started on shore" led the Allied aircrew to "report too optimistically on the results of the raid".{{sfn|Roskill|1960|p=357}} The Australian naval official historian [[G. Hermon Gill]] reached an identical conclusion in 1968. He also noted that Admiral [[Guy Royle]], the head of the Royal Australian Navy, told the Australian [[Advisory War Council]] on 23 May that Operation Transom had been of dubious value on military grounds as similar results could have been achieved by land-based aircraft without risking warships.{{sfn|Gill|1968|pp=418–419}} More recently, a 1990 work by [[Edwyn Gray]] and a 2009 work by [[David K. Brown|David Brown]] concurred with Roskill and judged that the raid had not been successful.{{sfn|Brown|2009|p=81}}{{sfn|Gray|1990|p=162}}

Other historians regard the attack as a victory for the Allies. The official historian of the overall British effort in South East Asia, [[Stanley Kirby|Stanley Woodburn Kirby]], wrote in 1962 that the Wonokromo oil refinery and other industrial facilities were set on fire, the naval dockyard and two other docks were bombed and twelve Japanese aircraft destroyed on the ground.{{sfn|Kirby|1962|p=382}} H.P. Willmott noted in 1996 that the raid caused "severe damage" to the Wonokromo oil refinery, "damage to the dockyard" and the sinking of a [[minesweeper]], a [[submarine chaser]] and a naval freighter.{{sfn|Willmott|1996|p=161}} [[Jürgen Rohwer]] stated in 2005 that twelve Japanese aircraft were destroyed on the ground, a small freighter was sunk and a [[patrol boat]] damaged beyond repair.{{sfn|Rohwer|2005|p=323}} In 2011 David Hobbs judged that the operation was successful, the Wonokromo oil refinery being "burnt out", naval dock installations damaged and a merchant ship sunk.{{sfn|Hobbs|2011|p=46}} Marcus Faulkner wrote in 2012 that Operation Transom "inflicted considerable damage".{{sfn|Faulkner|2012|p=224}} As is the case for the other air raids on Surabaya during World War II, it is not known how many civilian casualties resulted from Operation Transom.{{sfn|Dick|2003|p=79}}

Both Roskill and Hobbs agree that the attack provided the Royal Navy with important experience of carrier strike operations and exposure to superior American carrier tactics. Roskill observed that Somerville decided to copy the way in which ''Saratoga''{{'}}s crew conducted flight operations.{{sfn|Roskill|1960|p=358}} Hobbs identified other lessons the Royal Navy took away from the operation, including a need to plan to conduct at least two strikes against each target and the desirability of obtaining photo reconnaissance aircraft that could be flown from carriers.{{sfn|Hobbs|2011|pp=45–46}} Gray also noted that the operation, and especially the need to refuel in Western Australia, illustrated to the Royal Navy that it required an improved ability to replenish warships while they were at sea. This contributed to the acquisition of many supply ships that later supported the [[British Pacific Fleet]] during its operations against [[Okinawa Island|Okinawa]] and Japan in 1945.{{sfn|Gray|1990|pp=162–164}}

==References==
{{commonscat|Operation Transom}}
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===Citations===
{{reflist}}
===Works consulted===
* {{cite book |last1=Blair |first1=Clay |title=Silent Victory: The U.S. Submarine War Against Japan |date=2001 |publisher=Naval Institute Press |location=Annapolis, Maryland |isbn=978-1-55750-217-9 |author-link=Clay Blair}}
* {{cite book |last=Brown |first=David |title=Carrier Operations in World War II |year=2009 |publisher=Seaforth Publishing |location=Barnsley, Yorkshire |isbn=978-1-84832-042-0 |editor=Hobbs, David |author-link=David K. Brown}}
* {{Cite book |editor1-last=Dear |editor1-first=I.C.B. |editor1-link=I. C. B. Dear |editor2-last=Foot |editor2-first=M.R.D. |editor2-link=M. R. D. Foot |year=2001 |orig-year=1995 |title=The Oxford Companion to World War II |location=Oxford |publisher=[[Oxford University Press]] |isbn=978-0-19-860446-4}}
* {{cite book |last1=Dick |first1=H. W. |title=Surabaya, City of Work: A Socioeconomic History, 1900–2000 |date=2003 |publisher=Singapore University Press |location=Singapore |isbn=9789971692643}}
* {{cite book |last1=Evans |first1=Mark L. |last2=Grossnick |first2=Roy A. |title=United States Naval Aviation 1910–2010. Volume I: Chronology. |date=2015 |publisher=Naval History and Heritage Command, Department of the Navy |location=Washington, D.C. |isbn=978-0-945274-75-9 |url=https://www.history.navy.mil/content/history/nhhc/research/publications/publications-by-subject/naval-aviation-1910-2010.html#vol1}}
* {{cite book |last=Faulkner |first=Marcus |title=War at Sea: A Naval Atlas, 1939–1945 |year=2012 |publisher=Naval Institute Press |location=Annapolis, Maryland |isbn=978-1-59114-560-8}}
* {{cite book |last1=Fuller |first1=Richard |title=Shōkan: Hirohito's Samurai. Leaders of the Japanese Armed Forces, 1926–1945 |date=1992 |publisher=Arms and Armour |location=London |isbn=978-1-85409-151-2}}
* {{cite book |last=Gill |first=G. Hermon|author-link=G. Hermon Gill |title=Royal Australian Navy, 1942–1945 |url=https://www.awm.gov.au/collection/C1417314 |series=[[Australia in the War of 1939–1945]]|volume=Series 2 – Navy. Volume II|year=1968 |publisher=Australian War Memorial |location=Canberra|oclc=65475}}
* {{cite book |last1=Gray |first1=Edwyn |title=Operation Pacific: The Royal Navy's War against Japan, 1941–1945 |date=1990 |publisher=Naval Institute Press |location=Annapolis, Maryland |isbn=978-1-55750-650-4|author-link=Edwyn Gray}}
* {{cite book |last1=Hobbs |first1=David |title=The British Pacific Fleet: The Royal Navy's Most Powerful Strike Force |date=2011 |publisher=Naval Institute Press |location=Annapolis, Maryland |isbn=978-1-59114-044-3}}
* {{cite book|last=Kirby|first=S. Woodburn|author-link=Stanley Kirby|title=The War against Japan|volume=III: The Decisive Battles |publisher=HMSO|location=London|year=1962|series=[[History of the Second World War]]|oclc=632441219}}
* {{cite book |last1=Mawdsley |first1=Evan |title=The War for the Seas: A Maritime History of World War II |date=2019 |publisher=Yale University Press |location=New Haven, Connecticut |isbn=978-0-300-25488-4 |author-link=Evan Mawdsley}}
* {{cite book |last=Odgers |first=George |author-link=George Odgers|title=Air War Against Japan, 1943–1945 |orig-year=1957 |url=https://www.awm.gov.au/collection/RCDIG1070210/|series=Australia in the War of 1939–1945|volume=Series 3 – Air. Volume II|year=1968 |publisher=Australian War Memorial |location=Canberra|oclc=1990609}}
* {{cite book |last=Rohwer |first=Jürgen |author-link=Jürgen Rohwer |title=Chronology of the War at Sea: 1939–1945: The Naval History of World War Two |year=2005 |publisher=Naval Institute Press |location=Annapolis, Maryland |isbn=978-1-59114-119-8 |edition=Third revised}}
* {{cite book|last=Roskill|first=S.W.|author-link=Stephen Roskill|title=The War at Sea 1939–1945. Volume III: The Offensive Part I|year=1960|publisher=Her Majesty's Stationery Office|series=History of the Second World War|location=London|oclc=58588186}}
* {{cite book |last1=Willmott |first1=H.P. |title=Grave of a Dozen Schemes: British Naval Planning and the War Against Japan, 1943–1945 |date=1996 |publisher=Naval Institute Press |location=Annapolis, Maryland |isbn=978-1-55750-916-1}}
* {{cite book |last1=Winton |first1=John |title=Ultra in the Pacific: How Breaking Japanese Codes & Cyphers Affected Naval Operations Against Japan 1941–45 |date=1993 |publisher=Leo Cooper |location=London |isbn=978-0-85052-277-8 |author-link=John Winton}}

{{World War II city bombing}}

{{DEFAULTSORT:Transom, Operation}}
[[Category:South-East Asian theatre of World War II]]
[[Category:Naval battles of World War II involving France]]
[[Category:Naval battles of World War II involving the Netherlands]]
[[Category:1944 in Indonesia]]
[[Category:World War II aerial operations and battles of the Pacific theatre]]
[[Category:Aerial operations and battles of World War II involving the United Kingdom]]
[[Category:Naval battles and operations of World War II involving the United Kingdom]]
[[Category:April 1944 in Asia]]
[[Category:Indian Ocean operations of World War II]]
[[Category:Naval battles of World War II involving Japan]]
[[Category:Aerial operations and battles of World War II involving Japan]]
[[Category:Naval battles of World War II involving the United States]]
[[Category:Aerial operations and battles of World War II involving the United States]]
[[Category:Naval battles of World War II involving New Zealand]]