Escort Carriers During WW2
Contributor: Bob Bryant
Naval historians tend to focus on the contributions of the "fast carriers" operated during World War II. These were the 73 fleet carriers (CVs) and light carriers (CVLs). Less is written about the vital functions performed by 127 escort carriers (CVEs), including the so-called "hunter-killers" of the Atlantic and "little giants" of the Pacific. During the war, Allied CVEs performed virtually all the functions of the fleet and light carriers. They fought a major naval engagement against a powerful enemy battleship fleet, something the larger carriers did not experience. They supported invasions during which CVE-launched aircraft bombed enemy positions, spotted for gunship bombardment, and delivered aircraft to land bases after key airfields had been taken. They participated in raids on enemy installations, targeted shipping, sank submarines, protected fleets and convoys, and replenished aircraft and pilots for other carriers and land bases. Allied CVEs were also used for training pilots and, at the end of the war, helped repatriate troops and Prisoners of War (POWs) to their homes. In contrast, Japan used her 5 CVEs almost exclusively for convoy escort, transportation and training.
Types of Aircraft Carriers
Fleet Carriers. World War II CVs typically had standard displacements of 20,000 to 37,000 tons, were 700 to 850 feet in overall length, and could sail at 30 to 35 knots. US and Japanese fleet carriers were typically capable of carrying 50 to 90 aircraft into combat. British carriers were designed with armored decks, a measure that provided significantly greater protection against bombs and special attack planes, aka "kamikazes." However, the additional weight of the armor reduced their typical carrying capability to 35 to 55 aircraft. Thus their additional defensive measures limited their offensive striking power until Britain introduced a new carrier class late in the war.
Light Carriers. CVLs typically had standard displacements of 11,000 to 13,000 tons and 600 to 700 feet in overall length. With typical speeds of 28 to 31 knots, they were fast enough to keep up with the fleet carriers. Their smaller size, however, typically reduced their aircraft load to between 30 and 50. The design of light carriers commissioned immediately after the war began typically reflected the urgent need for fast carriers and took advantage of either the ship hulls being immediately available for conversion to aircraft carriers or of commercial shipyard capacity available to build them. While these carriers made important contributions to the war effort, their relatively small size made them operationally inefficient. Navel power in the Pacific theater was measured by the number of fleet carriers a navy had.
Escort Carriers. CVEs were typically smaller, slower, and lightly armored compared to their "fast" counterparts. Standard displacements normally ranged from 8,000 to 12,000 tons for Allied CVEs but averaged about 16,000 tons for Japanese CVEs, which were converted from passenger liners. With speeds from 15 to 24 knots, they were unable to keep up with the fast carriers. They were typically 450 to 600 feet in on overall length and carried 15 to 30 aircraft. CVEs were not usually included with naval battle fleets, but before the war was over, escort carriers had performed every function that the larger carriers had.
Merchant Aircraft Carriers. MACs were grain transports and oil tankers modified by the UK to have flight decks above their cargo holds. They displaced 8,000 to 9,000 tons and were typically 400 to 500 feet in overall length. They sailed at 11 to 12 knots, and carried 3 or 4 four aircraft along with their cargo.
Offensive and Defensive Capabilities
Unlike other warships, aircraft carrier armament was for principally for anti-aircraft defense rather that offense. Heavy anti-aircraft guns (3 to 5 inch) fired at aerial threats at longer range while lighter, rapid-fire anti-aircraft cannons (20 to 40 mm) fired at closer range. In comparison, destroyers, heavy cruisers, and battleships typically had anti-ship guns of 5, 8, and 14 to 18 inches respectively.
A carrier's offensive power was with the aircraft she carried. The number of such aircraft varied, even within a class of carriers, with the model of aircraft in the squadrons. Some models, such as those produced by Fairey Aviation, were larger than others. Some models, such as the Mitsubishi A5M "Claude" fighter and the Douglas SBD Dauntless dive-bomber, did not have folding wings. These factors reduced the number of aircraft that a carrier could accommodate. Some carriers had smaller hangers than others or, in the case of some earlier carriers, no hanger at all. CVE hanger deck length was typically between 45% and 60% of the flight deck length. Operating procedures for some navies provided for routinely keeping aircraft on deck rather than lowering them all down to the hanger for storage, enabling their carriers to have more aircraft aboard. The number of "operational" aircraft carried also varied. For example, Japan's CVE Shin'yo carried a total of 33 aircraft, but six were spares in various stages of disassembly, leaving only 27 ready for operations. Finally, the number of aircraft aboard depended upon the mission. Bogue-class CVEs could operate up to 24 aircraft when protecting convoys or hunting submarines but, when not themselves maintaining operational squadrons, could transport 90 aircraft.
Allied Escort Carrier Development
Early in World War II, Allied convoys in large areas of the Atlantic Ocean could not be protected from Axis air and submarine attack using land-based Allied aircraft from airfields in Canada, Iceland, and the United Kingdom (UK). Nor were there enough Allied aircraft carriers to include them with convoys in order to provide carrier-launched aircraft protection in those ocean gaps. To improve convoy protection, the Allies made plans for producing relatively small, "escort carriers" typically having 15 to 30 aircraft compared to 30 to 90 aircraft for the larger, faster carriers. While too slow to keep up with the larger carriers, the CVEs would keep pace with the merchant fleets they were expected to protect.
Design of all but a handful of CVEs was principally dictated by how quickly they could be brought into action. As early as 1938, the Imperial Japanese Navy (IJN) anticipated additional needs for carriers and subsidized construction of passenger liners so that they could be readily converted. During periods early in the Atlantic war, German U-boats were sinking Allied merchant ships faster than they could be produced. Accordingly, from 1941 to 1943, Allied merchant ships, passenger liners, and tankers, both in service and under construction, were converted to become escort carriers as quickly as possible. It was not until mid-1944 that the Commencement Bay-class, with a design optimized for service as an escort carrier, entered the war.
For a summary of CVE specifications by class, see the link to a table at end of this article. A link is also provided for a table summarizing models of aircraft deployed on aircraft carriers during the war.
FACs, CAMs, MACs. Until CVEs could become available, the UK took three interim measures for rapidly providing aircraft protection to convoys out of range of Allied land bases.
First, in 1940-1941, the UK converted three ocean boarding vessels, a seaplane tender, and an auxiliary aircraft cruiser to become Fighter Catapult Ships (FACs). Each such ship had a single aircraft, a Fairey Fulmar fighter, which could be launched using a catapult. No provision was made for the FACs to recover aircraft. After completing their attack, these planes were ditched in the ocean and their pilots recovered by other ships. Three of these five FACs were sunk in 1941.
Second, beginning in 1941, the UK converted 35 commercial and military transport ships to Catapult Aircraft Merchant ships (CAMs). Like the FACs, the CAMs carried only one, catapult-launched aircraft for which there was no provision to recover. While in service in 1941 and 1942, the CAMs provided valuable service, making nine combat launches while with convoys in the North Atlantic and Arctic Oceans and downing nine German aircraft. As adequate numbers of CVEs became available in mid-1943, FAC and CAM ships were judged to be too vulnerable to German raiders and U-boats and were retired from service.
Third, between April 1943 and April 1944, the UK converted a total of 19 commercial grain transports and oil tankers to Merchant Aircraft Carriers (MACs). These ships transported critical supplies such as grain and oil in their holds but, in addition, carried three or four Fairey Swordfish torpedo bombers for defense. MACs had flight decks and were capable of recovering as well as launching aircraft. Not all had hangers or lifts, and aircraft had to be stored on the flight decks. Although these carriers, like their predecessors, were intended to be stopgap measures until enough CVEs became available, MACs proved effective and all but four of them continued in service until the end of the war in Europe.
USS Langley. The Langley was the first US aircraft and had been converted from a collier in 1922. She was converted to a seaplane tender in 1937 but retained about 350 feet of her flight deck. Langley was in the Pacific in late 1941when the US entered the war and was assigned to the American-British-Dutch-Australian naval forces. She was similar is size and capability to the CVEs to come and performed their typical functions, including anti-submarine patrols and transport of aircraft. While transporting 32 Curtis P-40 Warhawk fighters from Australia to Java in late February 1942, she was attacked by Mitsubishi G4M "Betty" bombers, hit with five bombs, and scuttled.
Audacity. In January 1941, the UK began rebuilding a captured German merchant ship that, by the summer, became the first operational CVE, the HMS Audacity. She carried six operational Grumman F4F Wildcat fighters, called Martlets by the British, and could store another eight. There was no hanger deck or lift, and aircraft were stored on the flight deck. She escorted four convoys to and from Gibraltar, defending principally against German U-boats and long-range Folke-Wulf Fw 200 Condor bombers, before being sunk in September 1941 by a torpedo from U-751.
Long Island-Class. In April 1941, the United States (US) began converting C-3 merchant shipping hulls to escort carriers. To get these CVEs operational as soon as possible, US President Roosevelt insisted upon conversions that could be completed in no more than three months. The first US-built CVE was the USS Long Island, commissioned in June 1941 and operational by September. She was capable of operating 30 aircraft.
The following November, the second US-built CVE, capable of operating 15 aircraft, was transferred under the Lend-Lease Act to the Royal Navy as the HMS Archer. Her operational squadrons variously included Fairey Swordfish and Martlets and she ferried Martlets and Curtiss P-40 Warhawks to fleet carriers and land bases.
Charger/Avenger-Class CVEs. Four more CVEs were then constructed in US shipyards, of which three were transferred to the UK. Carrier names along with the maximum number of operational aircraft carried were HMS Avenger (15), HMS Biter (21), HMS Dasher (15), and USS Charger (30). These carriers were referred to as Charger-class by the Americans and Avenger-class by the British. USS Charger spent most of its service in the Chesapeake Bay and was used principally for training pilots and crew. The UK ships typically carried a mix of Fairey Swordfish, Hawker Sea Hurricanes, Grumman Wildcats/Martlets, and Grumman Avengers.
Bogue/Attacker-Class and Bogue/Ruler-Class CVEs. Experience with the USS Long Island led to design improvements for the forty-five C-3 hull conversions that made up the Bogue-class CVEs. Forty-five Bogue class carriers capable of operating 19-24 aircraft were launched in the US between 1942 and 1943. The first 22 were converted from merchant ships that were completed or nearly completed. Eleven of these were transferred to the Royal Navy, where they were referred to as the Attacker-class. Another 23 were built as CVEs from the beginning. All of these were transferred to the Royal Navy and referred to as the Ruler-class or alternatively as the Ameer-class.
Sangamon-Class CVEs. At the same time that the C-3 merchant ships were being converted to Bogue-class CVEs, the same was being done with four fast fleet T-3 mercantile tanker hulls that became the Sangamon-class. These ex-oilers had longer flight decks, greater range, were faster, more stable, carried 25-32 aircraft, and carried more fuel than the Bogue-Class ships. These improvements made them the choice for escorting troops across the Atlantic for OPERATION TORCH, the invasion of North Africa, and their completion was expedited. Their extra fuel capacity later proved useful in the Pacific. After providing close combat support and combat air patrols for OPERATION GALVANIC, the invasion of the Gilbert Islands, three Sangamon-class carriers still had enough fuel between them to refuel 45 destroyers and two cruisers. More such CVEs might have been constructed, but the critical wartime need for more oilers prevented the conversion of additional mercantile tankers to warships.
Activity. HMS Activity was under construction as a refrigerated cargo ship but converted by the UK to an escort carrier in 1942. She carried 10 aircraft, typically Fairey Swordfish and Grumman Martlets. She served as a trainer and later escorted convoys and transported aircraft, personnel, and supplies.
Casablanca/Kaiser-Class CVEs. The critical need for protecting convoys led to mass production of Casablanca-class CVEs in Kaiser's US shipyards. These carriers carried 27 operational aircraft. Although the design incorporated some improvements, ships of this class were generally considered good enough but just barely. Fifty were commissioned between 1942 and 1944.
Pretoria Castle. Pretoria Castle was a passenger liner converted in 1939 to a Royal Navy Armed Merchant Cruiser. In this capacity, she provided convoy escort protection against German commerce raiders in the South Atlantic. In mid-1943, she was converted to an escort carrier capable of accommodating 21 aircraft. Her wartime service as a CVE included sea trials and training, but she saw no active combat.
Nairana-Class CVEs. The UK converted three merchant ships to CVEs, one each at shipyards in England, Scotland, and Northern Ireland. These were HMS Nairana, Vindex, and Campania. They came into use during 1944 and carried 15 to 20 aircraft. Although grouped together as a class, they were not from a common design. Standard displacement ranged from13,000 to 14,000 long tons and installed power from 11,000 to 13,000 horsepower.
Commencement Bay-Class CVEs. Everything that had been learned from earlier designs was taken into consideration for the Commencement Bay-class CVEs, which in effect were upgraded Sangamons. The engine room was partitioned to reduce the likelihood that a single hit could knock out both engines. The flight deck was strengthened so that it could accommodate the newer, heavier aircraft models. Elevators were faster and two catapults were included instead of just one. These CVEs were a little faster than the Sangamons, and the longer hanger deck enabled accommodating 34 operational aircraft. Nineteen of these carriers were commissioned beginning in November 1944 but only a few saw combat during World War II.
Japanese Escort Carrier Development
Taiyo-Class CVEs. Three escort carriers were converted from Nitta Maru class passenger-cargo liners built by Mitsubishi Shipbuilding & Engineering at Nagasaki. Taiyo, Un'yo, and Chkyo became operational as CVEs in September 1941, May 1942, and November 1942 respectively. Taiyo could accommodate 23 operational aircraft and 4 spares. Un'yo, and Chkyo could each accommodate a total of 30 aircraft. These CVEs were larger and faster than Allied CVEs but they lacked catapults and arresting gear. They were used almost exclusively for transporting aircraft, escorting convoys, and training pilots. During their service, these three CVEs were hit by US submarine torpedoes in a total of eight separate attacks, ultimately resulting in all three being sunk in 1944.
Shin'yo. This carrier was converted from the German passenger liner Sharnhorst, which had been trapped in Japan at the beginning of the war in Europe and was subsequently purchased by the IJN with the intention of using her as a troop ship. Following IJN carrier losses at Midway in June 1942, she was converted instead to a CVE and was similar to the Taiyo-class carriers. She did not become operational for convoy escort until November 1943. Shin'yo could accommodate 27 operational aircraft and 6 spares. Like the Taiyo-class carriers, she was sunk by US submarine torpedoes in 1944.
Kaiyo. Like Japan's other CVEs, this carrier was converted from a passenger liner, becoming operational as a CVE along with Shin'yo in November 1943. She could accommodate 24 aircraft, typically 18 fighters and 6 bombers, and served to ferry aircraft and escort convoys. Kaiyo ended her career bombed out and intentionally beached in Japan's Inland Sea, then serving only as an anti-aircraft platform.
Escort Carrier Production During the War
The Allies produced a total of 121 CVEs during the war, of which 10 were sunk. The Japanese produced a total of 5 CVEs during the war, all of which were sunk. (See table, below.)
Escort Carrier Functions And Operations
Allied CVEs were used in a wide variety of functions. Initially the critical need was for convoy escort, but CVEs were also envisioned from the beginning for additional operations, including combat roles. The UK's early intention for deployment of CVEs was 24 for convoy escort, 11 for assault operations, 7 for ferrying aircraft, and 2 for training. Ultimately, Allied CVEs performed all of the ten basic functions performed by fleet and light carriers except for anti-raider search and destroy operations. Operational examples for each of these functions are included in the following sections.
- Naval Battles. CVE's were never envisioned for deployment in front line, ship-to-ship combat with an enemy fleet. Their thin skin, light armament, and slow speed made them unsuitable for action that would involve direct exchanges of gunfire with other ships. A contemporary assessment of the "baby flattops" was that they were CVE, i.e., "Combustible, Vulnerable, and Expendable."
However, during OPERATION KING II, the Allied invasion of the Philippines, questionable USN command decisions and monumental communication failures resulted in a small group of Allied CVEs unexpectedly confronting a powerful Japanese fleet. As an IJN "decoy fleet" of carriers lured the large carriers and battleships of the powerful US Third Fleet away from the Philippines, another IJN fleet sailed through unguarded waters toward Leyte Gulf to disrupt the Allied landings there. Off Samar, this IJN fleet of 4 battleships, 8 cruisers and 11 destroyers bumped into and then engaged "Taffy 3", a USN support group consisting of only 6 CVEs, 3 destroyers, and 4 destroyer escorts. As surprised as the Japanese by the encounter, and under gunfire from battleships and cruisers, the CVEs launched their aircraft as fast as they could with whatever fuel and munitions were already loaded. Some planes had little or none but attacked nonetheless with what they had, which included some rockets, bombs, torpedoes, machine guns, depth bombs, and even handguns. Pilots without munitions or ammunition risked themselves and dived on the IJN warships anyway to harass them into taking evasive action. The escorting USN destroyers and destroyer escorts also reacted quickly to protect the retreating CVEs. With torpedoes and only 5" guns, they boldly charged the IJN gunships, including the Yamato with 18" guns, the largest warship afloat. Three of these brave USN escort ships were sunk. CVE Gambier Bay was also targeted by 8" and 18" shellfire and became the only USN aircraft carrier sunk by surface naval gunfire during the war. In return, CVE St. Lo became the only USN carrier to ever score a hit on an enemy warship with its own guns.
The confused and desperate running fight lasted two and a half hours. The aggressive US response blunted the Japanese attack and scattered their warships. The Japanese commander came to believe he was facing the main US fleet that had, in fact, been successfully lured away. He retreated. Potential catastrophe for the Allied invasion force at Leyte Gulf was averted through the courage and determination of these very much out-gunned CVEs and their escorts. On CVE Fanshaw Bay, which had been hit by four 8" shells, a signalman watching the Japanese gunships retreat was heard to yell, "Damn it, boys, they're getting away!"
Even after the IJN warships left the area, the threat to Taffy 3 and other nearby CVE groups had not ended. IJN submarines were prowling, and the first attacks of the war were being made by Japanese Special Attack Units (aka "kamikazes"). One such plane hit CVE St. Lo, sinking her. Overall, the Battle off Samar cost the Americans over 1,500 dead and five ships sunk. These personnel losses were greater than the combined total of Americans killed in all four of the major fleet carrier battles of 1942. When the attacks on retreating Japanese warships by aircraft from nearby CVE groups are included, the CVEs and their escorts had sunk three IJN heavy cruisers and damaged three others along with a destroyer.
- Invasions. CVE support for invasions involved such combat action by their air squadrons as softening up targets before troops landed, close air support for advancing troops, Combat Air Patrol (CAP) and anti-submarine cover for warships at or in transit to the invasion area, and spotting for gunship bombardment. CVEs were also used for replenishment of aircraft and pilots during the invasion, photo-reconnaissance, air delivery of supplies, and even for dropping propaganda leaflets.
In the Atlantic in November 1942, the Sangamon-class CVEs were rushed to completion to support OPERATION TORCH, the Allied invasion of North Africa. They would be the first US CVEs to see combat. Fighters and bombers from USS Sangamon attacked a key airdrome near Casablanca. Avenger torpedo bombers from USS Suwannee attacked the submarine base in Casablanca Harbor and attacked a cruiser and gun batteries. Her Wildcat fighters conducted CAPs and anti-submarine patrols to protect the fleet. Aircraft from USS Santee neutralized the airdrome at Marrakesh and did spotting for US warship's guns, photo-reconnaissance, and patrols searching for enemy cruisers and submarines, attacking one of the latter. P-40 Warhawk fighters transported by USS Chenango flew to key Moroccan airdromes after ground troops had secured them. Along with USS Ranger, the only US fleet carrier then in the Atlantic, the US carriers brought a total of 171 combat aircraft to the battle. Never before had an amphibious landing been attempted on a shore separated from its staging area by almost 4,000 miles of ocean.
In September 1943, UK Attacker-class escort carriers HMS Attacker, Battler, Hunter, and Stalker along with the light carrier HMS Unicorn supported OPERATION AVALANCHE, the invasion of Italy at Salerno. Carrier aircraft provided protective cover for the landings until the landing force secured enemy airfields. Once the airfields were taken, aircraft flew to them from the carriers and provided air cover for landing operations from those airfields. Together, there were 109 aircraft from the four CVEs. Their aircraft losses were high, and aircraft was flown in to replace those losses from two fleet carriers, HMS Illustrious and Formidable, which maintained station further away from the action. This replenishment of CVEs by CVs was the reverse of the typical procedure then in use in the Pacific, where CV aircraft and pilot losses were replenished by CVEs. The usefulness of the CVE aircraft for providing air cover during the Salerno landings led the UK to develop "assault CVEs" to optimize them for this role.
For OPERATION OVERLORD, the invasion of northern France at Normandy in June 1944, three Allied CVEs (HMS Emperor, Tracker, and Pursuer) were deployed west of the landing area to discourage interference by U-boats. Two months later, for OPERATION DRAGOON, 200 aircraft launched from nine Allied CVEs supported the invasion of southern France at Provence by spotting for naval gunfire and bombing retreating German forces.
In the Pacific, the first use of aircraft carriers for close air support of invasion troops was done during OPERATION LANDCRAB, the operation to retake Attu in the Aleutian Islands during May 1943. This was only the third US amphibious assault of the war. The operation was also one of the earliest uses of "leapfrogging", whereby the Japanese position at Kiska was bypassed with the expectation that it would wither on the vine or be evacuated after Attu fell. A single escort carrier, USS Nassau, was included for this operation because persistent fog and wind conditions might prevent land-based aircraft from being available. Having an offshore launching capability increased options. Nassau's Wildcat fighters bombed and strafed enemy positions as well as conducted photo-reconnaissance, typically in foul weather. Munitions included "oil bombs", a forerunner of napalm bombs used extensively later in the war.
Beginning in late 1943 as US forces moved across the Central Pacific, CVEs helped support virtually every amphibious assault with fleet protection, air support for ground forces, spotting for naval bombardment, and/or replenishment of aircraft and pilots. These operations included the invasions of the Gilbert Islands, Marshall Islands, Mariana Islands, Palau Islands, the Philippines, Iwo Jima, and Okinawa. OPERATION STALEMATE, the assault on Peleliu in September 1944, was supported by 3 CVs, 5 CVLs, and 11 CVEs. For this operation, the escort carriers were being employed for the first time as group under a single, common command. It was perceived that once the larger carriers had helped establish a beachhead and largely reduced enemy air strength in an area, the CVEs could completely handle the full support of a major operation.
When Japanese Special Attack Units (aka "kamikazes") became active in late 1944, CVEs were perceived to be particularly vulnerable. Their invasion support functions required them to remain off hostile shores for lengthy periods without the speed, maneuverability, and larger defensive screen typically enjoyed by the larger carriers. During the war, CVEs took 20 hits from special attack planes severe enough to require repairs that resulted in lost operational time. Three escort carriers, USN St. Lo, Ommaney Bay, and Bismarck Sea, were sunk. Special attack planes also caused lost operational time 28 times for the larger carriers, but none were sunk. Since the missions for special attack aircraft involved only one-way flights, their effective range was doubled. One such plane smashed into a carrier, killing 27, at the US logistics center at Ulithi Atoll, having flown over 1,500 miles from Kanoya airbase on Japan.
- Raids. This function involved attacks to degrade enemy positions without the intent of invading to secure a permanent position. Escort carriers were typically ten knots slower than CVs and CVLs, the "fast carriers." This made them more vulnerable during hit-and-run raiding. Nonetheless, Allied CVEs participated in raids to cripple enemy warships, disrupt enemy air operations, and divert enemy attention away from principal objectives.
UK initiatives kept the German battleship Tirpitz confined to Norwegian ports for most of the war. Anchored at Kaafjord in northern Norway, Tirpitz was the largest battle ship ever produced in Europe and, with her 15" guns, was viewed by the Allies as a ongoing threat to convoys to Russia. As six months of repairs resulting from an midget submarine attack were nearing completion, the OPERATION TUNGSTON raid was undertaken in April 1944 to keep Tirpitz disabled. While aircraft from two RN fleet carriers bombed her, aircraft from CVEs HMS Emperor, Pursuer, and Searcher strafed nearby anti-aircraft batteries as well as the battleship herself. CVE HMS Fencer provided CAP and conducted anti-submarine patrols during the raid. As a result of damage inflicted, it would take over three more months for Tirpitz to be combat-ready again. Another raid against her in August, OPERATION GOODWOOD, involved multiple fleet carriers and CVEs Nabob and Trumpeter. Multiple raids after that kept Tirpitz disabled, preventing her from ever rejoining the war effort. Land based bombers finally sank her in November 1944.
Beginning in early April 1945, the British Pacific Fleet (BPF) conducted raids for 82 consecutive days on the Japanese airfields on the Sakishima Islands. These were principally intended to reduce interference with OPERATION ICEBERG, the invasion of Okinawa, by Japanese Special Attack Units (aka "kamikazes"). Airfields were rocketed, bombed, and bombarded by a fleet that included five RN fleet carriers and twenty-five RN and USN escort carriers. When the main fleet retired for refueling, the large Sangamon-class CVEs continued the raiding operations, day and night. Also engaged in these raids was the new USN Block Island of the new Commencement Bay-class of CVEs. It was captained and manned by seven hundred men from the CVE of the same name that had been sunk in the Atlantic in mid-1944.
Also in April 1945, CVEs HMS Empress and Shah from the Far East Fleet based at Ceylon (now Sri Lanka) conducted raids on the Andaman Islands to prevent Japanese interference with OPERATION BISHOP, the UK landings at Rangoon, Burma.
For OPERATION WANDERER in June 1944, escort carriers HMS Striker and Fencer raided the Norwegian coast to keep German U-boats away from the Normandy where they might interfere with OPRATION OVERLORD.
- Anti-Shipping and Blockading. These actions included anti-shipping sweeps, operations to sink enemy merchant shipping, and mine laying by aircraft.
Beginning in 1944, CVEs participated in many operations to sink German ships and degrade port facilities along the coast of Norway. In April, HMS Pursuer aircraft took part in a successful attack on a German convoy off Bodo, hitting four supply vessels and one of the escorts with bombs. The following month, HMS Searcher, Striker, and Emperor hit a convoy and shore targets at Kristiansund (OPERATION HOOPS). Similar strikes continued by several other CVEs through to the end of the war when CVEs HMS Searcher, Queen, and Trumpeter hit shipping and the U-boat base at Kilbotn (OPERATION JUDGEMENT) in May of 1945. Strikes were also made on Axis shipping in the Aegean (OPERATION OUTING) by seven UK CVEs as the Germans withdrew from Crete in September 1944.
- Anti-Raider. The threat from surface raiders had virtually passed by the time CVEs became available. Only larger carriers had been involved in search and destroy action against them.
- Anti-Submarine Warfare. ASW included specialized operations such as deploying hunter-killer groups to search for and destroy submarines independently of invasion support or convoy escort operations.
In early 1943 when the number of CVEs was still limited, the UK and US favored different approaches for using available CVEs in ASW. The UK typically kept their CVEs close to convoys since protection of the merchant ships was their priority, not sinking submarines. In addition, it was reasoned that, if the objective was to find U-boats to sink, they could well be expected to come to the convoys. UK CVE operations were closely controlled centrally to optimize convoy escort efforts. Convoys were routed around known submarine concentrations and additional escorts were sent to strengthen the defense for convoys that were believed to be threatened.
The US, on the other hand, believed a complementary effort by independent CVEs to search out and destroy U-boats and their supply ships would also be effective. Disrupting refueling operations and sinking U-boat supply ships, such as "milk cow" submarines, reduced the patrol time for Axis attack submarines to find and sink Allied merchant ships before they had to return to their bases. US CVEs, led by officers with naval aviation experience, formed the center of hunter-killer groups that moved independently of convoys and independently of centralized control. They acted upon highly accurate intelligence about enemy submarines positions because the Allies were intercepting and decoding Axis naval transmissions. Almost from the beginning, the US used CVEs, screened by destroyers or destroyer escorts, for independent anti-submarine patrols. US escort carriers USS Bogue, Card, Core, and Croatan, guided to German submarine locations using intercepted German Navy transmissions, were highly successful as "hunter-killer" warships. During the war, seven USN hunter-killer CVEs and their escorts sank 54 U-boats, 31 by the CVE's aircraft.
Both the UK and US approaches for using escort carriers proved highly successful for sinking submarines in the Atlantic. Together, ship borne aircraft and their surface ship escorts sank 93 U-boats.
After the turning point for the Atlantic anti-submarine war in May 1943, and with increasing numbers of CVEs becoming available, the UK also deployed hunter-killer groups centered on CVEs. In early 1944, HMS Vindex began focused ASW as well as convoy escort duty in the Atlantic and Arctic Oceans and sank a total of four U-boats during her career.
Beginning in February 1945 around Iwo Jima and later around Okinawa in the Pacific theater, CVEs USS Tulagi and Anzio were deployed for independent ASW patrolling. The work was monotonous, with hours and days passing without any sightings. It also was tiring, with aircrews often conducting ground support work during the day and anti-submarine work at night. When Japanese submarines were located with radar and then sighted on the surface, they were attacked with machine gun, rockets, depth bombs and/or "Fido" acoustic homing torpedoes. Escorting surface ships might be called in to make "hedgehog" forward-thrown ASW munitions. Sonobuoys were dropped into the water to listen for sounds of submarines escaping or breaking up.
- Convoy and Fleet Escort. This function involved using escort carrier air squadrons for CAP and ASW to protect transports and warships transiting war zones. The greatest initial Allied need for CVEs was to protect merchant shipping in convoys. To improve protection from raider and U-boat attacks, thousands of merchant ships traveled in thousands of convoys protected by thousands of escorts. UK naval escorts alone completed 13,200 separate trans-Atlantic voyages to protect merchant ships.
The first use of a carrier escort for convoy protection was made in September 1941 when Britain's first escort carrier, HMS Audacity, escorted a convoy outbound from Britain to Gibraltar. Five of the twenty-five merchant ships were sunk by U-boats, but a German Luftwaffe attack by land-based aircraft from an airfield in France was repulsed. A German Focke-Wulf Condor bomber was shot down. Later that month, escorting another convoy to Gibraltar, Audacity's aircraft conducted anti-submarine sweeps and fought off German Condors, shooting down four but losing one RN Martlet fighter in the exchange. The return convoy around mid-December consisted of 32 merchant ships and 17 escorting warships ships, including Audacity and three destroyers. Audacity's Martlet fighters shot down two Condors without a loss and spotted German submarine U-131, which was subsequently depth bombed by screening warships and scuttled. This was the first instance of escort carrier-launched aircraft guiding another escort warship to a submarine that resulted in a kill. It demonstrated the potential for routinely including carriers as convoy escorts. The convoy fought through a total of nine U-boats, sinking five and losing three merchant ships, a destroyer and, finally, HMS Audacity, which was torpedoed by U-751. Even with the losses, the Admiralty considered the convoy a success. Audacity's aircraft reduced the size of the unprotected area on the Gibraltar convoy route and demonstrated the importance of escort carriers that carried with them their own fighter and anti-submarine protection. On the German side, the severe losses of U-boats during this operation discouraged Admiral D´┐Żnitz from authorizing such attacks unless the U-boats in a wolfpack outnumbered convoy escort vessels.
While on convoy escort duty in the North Atlantic in May 1943, a Fairey Swordfish from HMS Archer sank U-752 with a "rocket spear." This was the first sinking of a U-boat with this newly developed weapon and only the second submarine sinking by an aircraft operating from an escort carrier.
In January 1944, HMS Chaser became the first CVE to escort a large convoy to Russia. Her Wildcat fighters helped drive off German aircraft and her Swordfish bombers attacked German submarines. One Swordfish spotted a U-713 on the surface and called in an escorting destroyer that then sank her with depth bombs. Another U-boat was sunk by land-based aircraft. All 43 merchant ships of the convoy reached Kola Inlet safely in spite of the14 U-boats deployed against them. During the return convoy, one of Chaser's Swordfish caught U-472 on the surface, damaged her with bombs and rockets, and called in an escorting destroyer that sank her with gunfire. Patrolling Swordfish subsequently sank U-366 and U-973. All merchant ships except one arrived at homeport safely.
As the Allies advanced over land in the Atlantic theater and over the ocean in the Pacific theater, a growing number of CVEs provided convoy protection and transportation services for the ever-lengthening supply lines.
- Transportation. This function involved transporting personnel and/or aircraft to and within war zones. It does not include transportation or replenishment accomplished as part of supporting specific invasions.
In the Atlantic, CVEs helped sustain momentum after successful invasions. For example, USS Croatan ferried aircraft and plane crews to Casablanca to support North African operations.
In the Pacific, Japanese CVEs made regular trips to forward bases with aircraft and aircrews to support advances and defensive operations in the South Pacific area. CVE USS Long Island delivered the first aircraft to Henderson Field on Guadalcanal after the US Marines secured a tenuous toehold there in August 1942. Two months later, USS Copahee delivered another 38 marine fighters and dive-bombers in time for them to participate in the Battle of Cape Esperance and in the third and final Japanese attempt to retake that island. After the UK returned to the Pacific in 1945, HMS Arbiter was one of seven CVEs that ferried replenishment aircraft in support of the British Pacific Fleet (BPF).
Transportation duty was not without its dangers. IJN Chkyo was used principally to transport aircraft to and from the principal Japanese naval base at Truk in the Caroline Islands, and was sunk by a submarine torpedo en route to Japan. Taiyo was used to transport aircraft to distant Japanese bases as well as for convoy escort. She survived damaged twice from US submarine torpedoes attacks but was sunk by the third attack. USN CVEs carrying replacement aircraft for Halsey's Third fleet in December 1944 got caught in a typhoon with steady winds of over 100 knots and wave heights variously reported as tall as 60 to 100 feet. Carriers reported rolling as much as 45 to 60 degrees, and waves washed over flight decks 57 feet above the waterline. Aircraft on the CVE flight and hanger decks broke lose from their moorings, were swept overboard, and crashed into bulkheads, starting fires. Bombs exploded. Fire on CVE USS Monterey was from bow to stern. Lt. (j.g.) Jerry Ford, future US president, led a fire brigade down to the hanger deck to rescue the wounded and put out the fire. USS Monterey, Cowpens, Cape Esperance, and San Jacinto had most of their aircraft go overboard or become damaged beyond repair. In total, 146 aircraft were lost. Three destroyers capsized and a total of 800 men were lost. USS Nehenta Bay sustained damage in this typhoon and in another bout with heavy weather the following month (only 30 foot waves that time).
- Training and Trials. Some CVEs were mostly dedicated to pilot training and carrier trials. CVE USS Charger spent most of the war in the Chesapeake Bay with this focus. IJN Shinyo also spent considerable time in pilot training activities. HMS Pretoria Castle was used exclusively for trials and training.
- Repatriate Troops. After hostilities ended, CVEs were used to help return troops and prisoners of war to their homeports. A few US CVEs, including USS Block Island and Santee, were involved in the Recovery of Allied Military Personnel (RAMP) operation. HMS Vindex brought prisoners of war from Hong Kong back to Australia and the UK. The US Navy's OPERATION MAGIC CARPET for returning other troops involved 46 CVEs.
The combatants differed in the functions they emphasized for CVE use, in part as a result of the challenges presented by their principal theater of operations. The table below indicates the percentage of carriers each combatant used for each function. For example, the US Navy operated a total of 78 CVEs during the war. Fifty-three percent of these carriers participated in invasions at one time or another. Twenty-four percent were involved in ASW. Percentages for CVs and CVLs are included for comparison.
Functions Performed by Aircraft Carriers During World War II
|Number of Carriers||Naval Battles||Invasions||Raids||Anti-Ship||Anti-Raid||Anti-Sub||Convoy Escort||Trans.||Training||Repat.|
|CVs & CVLs|
During the war, seven US, three UK, and five Japanese CVEs were sunk. All three UK and one US CVE were sunk in the Atlantic theater. The rest were sunk in the Pacific theater.
Causes for Escort Carriers Being Sunk During World War II
|Escort Carrier||Date Sunk||Location Sunk||People Lost||Sunk By|
|1||HMS Audacity||21-Dec-41||North Atlantic off Spain||73||3 Torpedoes from German Sub U-751|
|2||USS Langley (SPC)||27-Feb-42||Off Java||>16||Bombs from Bali-based bombers|
|3||HMS Avenger||15-Nov-42||Off Algeria||514||1 Torpedo from Sub German U-155|
|4||HMS Dasher||27-Mar-43||Off Scotland||379||Internal explosion|
|5||IJN Shin'yo||17-Nov-43||East China Sea||1,130||4 Torpedoes from Sub USS Spadefish|
|6||USS Liscome Bay||24-Nov-43||Off Makin Island||702||1 Torpedo from Sub IJN I-175|
|7||IJN Chkyo||4-Dec-43||Off Japan||1,250||Torpedoes from Sub USS Sailfish|
|8||USS Block Island||29-May-44||Off Canary Is.||6||3 Torpedoes from Sub German U-549|
|9||IJN Taiyo||18-Aug-44||Off Philippines||790||1 Torpedoes from Sub USS Rasher|
|10||IJN Un'yo||17-Sep-44||Convoy HI-74 from Singapore||1,000e||2 Torpedoes from Sub USS Barb|
|11||USS Gambier Bay||25-Oct-44||Off Samar||?||Gunfire from IJN Chikuma (and IJN Yamato?)|
|12||USS St. Lo||25-Oct-44||Off Samar||113||Special Attack Plane (aka "Kamikaze")|
|13||USS Ommaney Bay||4-Jan-45||Sulu Sea off Philippines||95||Special Attack Plane (aka "Kamikaze")|
|14||USS Bismarck Sea||21-Feb-45||Iwo Jima||318||2 Special Attack Planes (aka "Kamikazes")|
|15||IJN Kaiyo||24-Jul-45||Beppu Bay, Japan||20||Mines and UK/BPF Bombs|
During the war, there were 104 incidents resulting in damage to CVEs that required their sailing to repair facilities and thereby reducing time available for operations. The causes for the damage are shown in the following table. Damage incidents for the "fast carriers" (CVs and CVLs) are shown for comparison.
Causes for Damage to Aircraft Carriers Resulting in Lost Operational Time
|Cause For Lost Operational Time||Fast||CVEs||Fast||CVEs|
|Aerial Bombs & Torpedoes||7||0||4%||0%|
|Aerial & Submarine Torpedoes||1||0||1%||0%|
|Sub-Total Aerial Bombs & Torpedoes||58||6||42%||6%|
|Special Attack Units (aka "kamikazes")||28||20||20%||19%|
|Sub-Total Combat Activity||101||43||74%||41%|
|Storms & Typhoons||11||19||8%||18%|
|Sub-Total Other Causes||36||61||26%||59%|
Escort Carrier Classes During WW2
Carrier Aircraft Used During WW2
Aircraft Carrier Operations During WW2
Barlow, Jeffrey G. (2013). "The Navy's Escort Carrier Offensive". Naval History Magazine, December 2013, Volume 27, Number 6. U.S. Naval Institute
Drury, Bob and Tom Clavin (2007). Halsey's Typhoon
Mason, Lt Cdr Geoffrey B, RN (2010). "Escort (and Light Fleet) Aircraft Carriers". Service Histories Of 1,000 Royal Navy Warships in World War 2
Morison, Samuel Eliot (1963). The Two-Ocean War
Roskill, Stephen (1960). The Navy At War
Toppan, Andrew (2020). The Dictionary of American Naval Fighting Ships (DANFS Online)
Tully, Anthony (2020). Kido Butai!- Stories and Battle Histories of the IJN's Carrier Fleet
Y'Blood, William T. (1983). Hunter-Killer
Y'Blood, William T. (1987). Little Giants
Directory of American Naval Fighting Ships
Naval War in the Pacific 1941-1945
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