The escort carrier or escort aircraft carrier (U.S. hull classification symbol CVE), also called a "jeep carrier" or "baby flattop" in the United States Navy (USN) or "Woolworth Carrier" by the Royal Navy, was a small and slow type of aircraft carrier used by the Royal Navy, the United States Navy, the Imperial Japanese Navy and Imperial Japanese Army Air Force in World War II. They were typically half the length and a third the displacement of larger fleet carriers, slower, more-lightly armed and armored, and carried fewer planes. Escort carriers were most often built upon a commercial ship hull, so they were cheaper and could be built quickly. This was their principal advantage as they could be completed in greater numbers as a stop-gap when fleet carriers were scarce. However, the lack of protection made escort carriers particularly vulnerable, and several were sunk with great loss of life. The light carrier (U.S. hull classification symbol CVL) was a similar concept to the escort carrier in most respects, but was fast enough to operate alongside fleet carriers.
Escort carriers were too slow to keep up with the main forces consisting of fleet carriers, battleships, and cruisers. Instead, they were used to escort merchant ship convoys, defending them from enemy threats such as submarines and planes. In the invasions of mainland Europe and Pacific islands, escort carriers provided air support to ground forces during amphibious operations. Escort carriers also served as backup aircraft transports for fleet carriers, and ferried aircraft of all military services to points of delivery.
In the Battle of the Atlantic, escort carriers were used to protect convoys against U-boats. Initially escort carriers accompanied the merchant ships and helped to fend off attacks from aircraft and submarines. As numbers increased later in the war, escort carriers also formed part of hunter-killer groups that sought out submarines instead of being attached to a particular convoy.
In the Pacific theater, CVEs provided air support of ground troops in the Battle of Leyte Gulf. They lacked the speed and weapons to counter enemy fleets, relying on the protection of a Fast Carrier Task Force. However, at the Battle off Samar, one U.S. task force of escort carriers and destroyers managed to successfully defend itself against a much larger Japanese force of battleships and cruisers. The Japanese met a furious defense of carrier aircraft, screening destroyers, and destroyer escorts.
Of the 151 aircraft carriers built in the U.S. during World War II, 122 were escort carriers, though no examples survive. The Casablanca class was the most numerous class of aircraft carrier, with 50 launched. Second was the Bogue class, with 45 launched.
In the early 1920s, the Washington Naval Treaty imposed limits on the maximum size and total tonnage of aircraft carriers for the five main naval powers. Later treaties largely kept these provisions. As a result, construction between the World Wars had been insufficient to meet operational needs for aircraft carriers as World War II expanded from Europe. Too few fleet carriers were available to simultaneously transport aircraft to distant bases, support amphibious invasions, offer carrier landing training for replacement pilots, conduct anti-submarine patrols, and provide defensive air cover for deployed battleships and cruisers. The foregoing mission requirements limited use of fleet carriers' unique offensive strike capability demonstrated at the Battle of Taranto and the Attack on Pearl Harbor. Conversion of existing ships (and hulls under construction for other purposes) provided additional aircraft carriers until new construction became available.
Conversions of cruisers and passenger liners with speed similar to fleet carriers were identified by the U.S. as "light aircraft carriers" (hull classification symbol CVL) able to operate at battle fleet speeds. Slower conversions were classified as "escort carriers" and were considered naval auxiliaries suitable for pilot training and transport of aircraft to distant bases.
The Royal Navy had recognized a need for carriers to defend its trade routes in the 1930s. While designs had been prepared for "trade protection carriers" and five suitable liners identified for conversion, nothing further was done mostly because there were insufficient aircraft for even the fleet carriers under construction at the time. However, by 1940 the need had become urgent and HMS Audacity was converted from the captured German merchant ship MV Hannover and commissioned in July 1941. For defense from German aircraft, convoys were supplied first with fighter catapult ships and CAM ships that could carry a single (disposable) fighter. In the interim, before escort carriers could be supplied, they also brought in merchant aircraft carriers that could operate four aircraft.
In 1940, U.S. Admiral William Halsey recommended construction of naval auxiliaries for pilot training. In early 1941 the British asked the U.S. to build on their behalf six carriers of an improved Audacity design, but the U.S. had already begun their own escort carrier. On 1 February 1941, the United States Chief of Naval Operations gave priority to construction of naval auxiliaries for aircraft transport. U.S. ships built to meet these needs were initially referred to as auxiliary aircraft escort vessels (AVG) in February 1942 and then auxiliary aircraft carrier (ACV) on 5 August 1942. The first U.S. example of the type was USS Long Island. Operation Torch and North Atlantic anti-submarine warfare proved these ships capable aircraft carriers for ship formations moving at the speed of trade or amphibious invasion convoys. U.S. classification revision to escort aircraft carrier (CVE) on 15 July 1943 reflected upgraded status from auxiliary to combatant. They were informally known as "Jeep carriers" or "baby flattops". It was quickly found that the escort carriers had better performance than light carriers, which tended to pitch badly in moderate to high seas. The Commencement Bay class was designed to incorporate the best features of American CVLs on a more stable hull with a less expensive propulsion system.
Among their crews, CVE was sarcastically said to stand for "Combustible, Vulnerable, and Expendable", and the CVEs were called “Kaiser coffins" in honor of Casablanca-class manufacturer Henry J. Kaiser. Magazine protection was minimal in comparison to fleet aircraft carriers. HMS Avenger was sunk within minutes by a single torpedo, and HMS Dasher exploded from undetermined causes with very heavy loss of life. Three escort carriers—USS St. Lo, Ommaney Bay and Bismarck Sea—were destroyed by kamikazes, the largest ships to meet such a fate.
Allied escort carriers were typically around 500 ft (150 m) long, not much more than half the length of the almost 900 ft (270 m) fleet carriers of the same era, but were less than 1⁄3 of the weight. A typical escort carrier displaced about 8,000 long tons (8,100 t), as compared to almost 30,000 long tons (30,000 t) for a full-size fleet carrier. The aircraft hangar typically ran only 1⁄3 of the way under the flight deck and housed a combination of 24–30 fighters and bombers organized into one single "composite squadron". By comparison, a late Essex-class fleet carrier of the period could carry 103 aircraft organized into separate fighter, bomber and torpedo-bomber squadrons.
The island (superstructure) on these ships was small and cramped, and located well forward of the funnels (unlike on a normal-sized carrier, where the funnels were integrated into the island). Although the first escort carriers had only one aircraft elevator, having two elevators (one fore and one aft), along with the single aircraft catapult, quickly became standard. The carriers employed the same system of arresting cables and tail hooks as on the big carriers, and procedures for launch and recovery were the same as well.
The crew size was less than 1⁄3 of that of a large carrier, but this was still a bigger complement than most naval vessels. U.S. escort carriers were large enough to have facilities such as a permanent canteen or snack bar, called a gedunk bar, in addition to the mess. The bar was open for longer hours than the mess and sold several flavors of ice cream, along with cigarettes and other consumables. There were also several vending machines available on board.
In all, 130 Allied escort carriers were launched or converted during the war. Of these, six were British conversions of merchant ships: HMS Audacity, Nairana, Campania, Activity, Pretoria Castle and Vindex. The remaining escort carriers were U.S.-built. Like the British, the first U.S. escort carriers were converted merchant vessels (or in the Sangamon class, converted military oilers). The Bogue-class carriers were based on the hull of the Type C3 cargo ship. The last 69 escort carriers of the Casablanca and Commencement Bay classes were purpose-designed and purpose-built carriers drawing on the experience gained with the previous classes.
Main article: list of escort carriers by country
Many escort carriers were Lend-Leased to the United Kingdom, this list specifies the breakdown in service to each navy.
In addition, six escort carriers were converted from other types by the British during the war.
The table below lists escort carriers and similar ships performing the same missions. The first four were built as early fleet aircraft carriers. Merchant aircraft carriers (MAC) carried trade cargo in addition to operating aircraft. Aircraft transports carried larger numbers of planes by eliminating accommodation for operating personnel and storage of fuel and ammunition.
|HMS Argus||1918||UK||14,000 tons (net)||20 kn (37 km/h; 23 mph)||18||converted liner|
|USS Langley||1922||United States||11,500 tons||15 kn (28 km/h; 17 mph)||30||converted collier|
|Hōshō||1923||Japan||7,500 tons (standard)||25 kn (46 km/h; 29 mph)||12||early fleet carrier|
|HMS Hermes||1924||UK||10,850 tons (standard)||25 kn (46 km/h; 29 mph)||12||early fleet carrier|
|HMS Audacity||1941||UK||11,000 tons||15 kn (28 km/h; 17 mph)||6||merchant conversion|
|USS Long Island, HMS Archer||1941||United States and UK||9,000 tons||17 kn (31 km/h; 20 mph)||15–21||merchant conversions|
|HMS Avenger, Biter, Dasher, USS Charger||1941||United States and UK||8,200 tons||17 kn (31 km/h; 20 mph)||15–21||merchant conversions|
|Taiyō, Unyō, Chūyō||1941||Japan||17,830 tons (standard)||21 kn (39 km/h; 24 mph)||27||converted liners|
|HMS Activity||1942||UK||11,800 tons (standard)||18 kn (33 km/h; 21 mph)||10–15||merchant conversion|
|Bogue class||1942||United States and UK||9,800 tons||18 kn (33 km/h; 21 mph)||15–21||45 conversions of C-3 merchant hulls|
|USS Sangamon, Suwanee, Chenango, Santee||1942||United States||11,400 tons (standard)||18 kn (33 km/h; 21 mph)||31||converted oilers|
|Akitsu Maru, Nigitsu Maru||1942||Japan (Army)||11,800 tons (standard)||20 kn (37 km/h; 23 mph)||8||liners converted to Hei-type landing craft carriers|
|Campania||1943||UK||12,400 tons (standard)||18 kn (33 km/h; 21 mph)||18||merchant conversion|
|Vindex||1943||UK||13,400 tons (standard)||16 kn (30 km/h; 18 mph)||15–20||merchant conversion|
|Nairana||1943||UK||14,000 tons (standard)||16 kn (30 km/h; 18 mph)||15–20||merchant conversion|
|Rapana class (Acavus, Adula, Alexia, Amastra, Ancylus, Gadila, Macoma, Miralda, Rapana)||1943||UK||12,000 tons||12 kn (22 km/h; 14 mph)||3||tankers converted to merchant aircraft carriers|
|Casablanca class||1943||United States||7,800 tons||19 kn (35 km/h; 22 mph)||28||50 built as escort aircraft carriers|
|Kaiyō||1943||Japan||13,600 tons (standard)||23 kn (43 km/h; 26 mph)||24||converted liner|
|HMS Pretoria Castle||1943||UK||17,400
|18 kn (33 km/h; 21 mph)||21||merchant conversion|
|Empire MacAlpine, Empire MacAndrew, Empire MacRae, Empire MacKendrick, Empire MacCallum, Empire MacDermott||1943||UK||8,000 tons (gross)||12 kn (22 km/h; 14 mph)||4||grain carrying merchant aircraft carriers|
|Empire MacCabe, Empire MacKay, Empire MacMahon, Empire MacColl||1943||UK||9,000 tons (gross)||11 kn (20 km/h; 13 mph)||3||tanker merchant aircraft carriers|
|Commencement Bay class||1944||United States||10,900 tons||19 kn (35 km/h; 22 mph)||34||19 built as escort aircraft carriers|
|Shin'yō||1944||Japan||17,500 tons||22 kn (41 km/h; 25 mph)||33||converted liner|
|Yamashio Maru class||1945||Japan (Army)||16,119 tons (standard)||15 kn (28 km/h; 17 mph)||8||converted tanker|
|Kumano Maru||1945||Japan (Army)||8,258 tons (standard)||19 kn (35 km/h; 22 mph)||8–37||Type M cargo ship converted to Hei-type landing craft carrier|
|Bogue-class escort carrier||Independence-class light carrier||Essex-class fleet carrier||Illustrious-class fleet carrier|
|Length:||495 ft (151 m)||625 ft (191 m)||875 ft (267 m)||740 ft (226 m)|
|Beam:||69 ft (21 m)||72 ft (22 m)||92 ft (28 m)||95 ft (29 m)|
|Displacement:||9,800 t||11,000 t||27,100 t||23,000 t|
|Armament||1x 5-inch/38-caliber gun, light AA||light AA||12x 5-inch/38-caliber guns, light AA||16x QF 4.5-inch Mk I – V naval guns|
|Armor||None||50–125 mm||150–200 mm||75 mm deck|
|Speed:||18 kn (33 km/h; 21 mph)||32 kn (58 km/h; 36 mph)||33 kn (61 km/h; 38 mph)||31 kn (56 km/h; 35 mph)|
|Crew:||850||1,569||3,448||817 + 390|
The years following World War II brought many revolutionary new technologies to naval aviation, most notably the helicopter and the jet fighter, and with this a complete rethinking of its strategies and ships' tasks. Although several of the latest Commencement Bay-class CVE were deployed as floating airfields during the Korean War, the main reasons for the development of the escort carrier had disappeared or could be dealt with better by newer weapons. The emergence of the helicopter meant that helicopter-deck equipped frigates could now take over the CVE's role in a convoy while also performing their usual role as submarine hunters. Ship-mounted guided missile launchers took over much of the aircraft protection role, and in-flight refueling eliminated the need for floating stopover points for transport or patrol aircraft. Consequently, after the Commencement Bay class, no new escort carriers were designed, and with every downsizing of the navy, the CVEs were the first to be mothballed.
Several escort carriers were pressed back into service during the first years of the Vietnam War because of their ability to carry large numbers of aircraft. Redesignated AKV (air transport auxiliary), they were manned by a civilian crew and used to ferry whole aircraft and spare parts from the U.S. to Army, Air Force and Marine bases in South Vietnam. However, CVEs were useful in this role only for a limited period. Once all major aircraft were equipped with refueling probes, it became much easier to fly the aircraft directly to its base instead of shipping it.
The last chapter in the history of escort carriers consisted of two conversions: as an experiment, USS Thetis Bay was converted from an aircraft carrier into a pure helicopter carrier (CVHA-1) and used by the Marine Corps to carry assault helicopters for the first wave of amphibious warfare operations. Later, Thetis Bay became a full amphibious assault ship (LHP-6). Although in service only from 1955 (the year of her conversion) to 1964, the experience gained in her training exercises greatly influenced the design of today's amphibious assault ships.
In the second conversion, in 1961, USS Gilbert Islands had all her aircraft handling equipment removed and four tall radio antennas installed on her long, flat deck. In lieu of aircraft, the hangar deck now had 24 military radio transmitter trucks bolted to its floor. Rechristened USS Annapolis, the ship was used as a communication relay ship and served dutifully through the Vietnam War as a floating radio station, relaying transmissions between the forces on the ground and the command centers back home. Like Thetis Bay, the experience gained before Annapolis was stricken in 1976 helped develop today's purpose-built amphibious command ships of the Blue Ridge class.
Unlike almost all other major classes of ships and patrol boats from World War II, most of which can be found in a museum or port, no escort carrier or American light carrier has survived; all were destroyed during the war or broken up in the following decades. The Dictionary of American Naval Fighting Ships records that the last former escort carrier remaining in naval service—USS Annapolis—was sold for scrapping 19 December 1979. The last American light carrier (the escort carrier's faster sister type) was USS Cabot, which was broken up in 2002 after a decade-long attempt to preserve the vessel.
Later in the Cold War the U.S.-designed Sea Control Ship was intended to serve a similar role; while none were actually built, the Spanish aircraft carrier Principe de Asturias and the Thai HTMS Chakri Naruebet are based on the concept.