US Navy Escort Aircraft Carriers
The United States Navy in World War II
NOTE ON NOMENCLATURE
The following abbreviations are used in this article: AA (antiaircraft), DD (destroyer), DE (destroyer escort), DP (dual-purpose surface/AA gun), RN (Royal Navy), USN (United States Navy). The F4F Wildcat fighter was designed and originally produced by Grumman. When that company switched to production of the follow-on F6F Hellcat, responsibility for Wildcat production passed to General Motors, and the Wildcats it produced were designated FM. Similarly, when TBF Avenger torpedo bomber production passed from Grumman to General Motors, the aircraft’s designation became TBM. To avoid confusion, the designations F4F and TBF are used throughout this article.
The air group operating from escort carriers was designated as a Composite Squadron (VC), e.g. VC-10, assigned to USS Gambier Bay (CVE 73). The USN initially classified the jeep carriers as auxiliary aircraft escort vessels (AVG). In early 1942 they were reclassified as auxiliary aircraft carriers (ACV), and in mid-1943 they became escort aircraft carriers (CVE). Again to avoid confusion, the CVE classification is used throughout this article.
During World War II, the US Navy operated three categories of aircraft carriers: fleet carriers (CV), light fleet carriers (CVL) and escort aircraft carriers (CVE). The CVs and CVLs were strike carriers designed for offensive operations. CVEs—the jeep carriers as they were nicknamed—were either conversions of civilian merchant ships or new construction based on mercantile designs. As such they were significantly smaller and slower than the CVs and CVLs
The CVE’s origins may be traced to World War I, when various merchant vessels were taken into naval service for conversion to seaplane carriers. The primary user was Britain’s Royal Navy, which commissioned around a dozen such ships. A typical example was HMS Empress, a former cross-Channel steamer that could carry six seaplanes. Most of these ships had no flight deck, the aircraft being handled by cranes. They proved useful, however, and in the 1930s the Admiralty had plans to requisition five passenger liners for conversion into auxiliary carriers for service as convoy escorts, training ships and aircraft transports. Nothing was done, however, since at the time the Royal Navy possessed insufficient aircraft to provide even its fleet carriers with full air groups.
Only with the onset of World War II did Britain embark upon an auxiliary carrier program. A number of merchant ships were requisitioned and converted, the first of which was HMS Audacity, formerly the German cargo ship Hannover, which had been captured in March 1940. Audacity had a full-length flight deck but no island, catapult or internal hanger, her eight aircraft being carried on deck. Despite these unsatisfactory features she operated successfully in the Atlantic, providing effective air cover for convoys between the UK and Gibraltar, until she was torpedoed and sunk by a U-boat in December 1941.
At first the CVE concept was looked upon with disfavor by the USN, which preferred large fleet carriers. But the need for additional carriers in 1942 led first to the development of the so-called light fleet carriers built on cruiser hulls and then to a series of small auxiliary carriers, the first of which was USS Long Island, formerly the cargo ship Mormacmail. She was acquired by the Navy and converted in 1941. The initial intention was to employ her as an aircraft transport. After completion, however, she received an air group and embarked upon a series of trials to test the concept of the escort aircraft carrier. Long Island was soon joined by a sister ship, USS Charger, which had originally been earmarked for transfer to the RN. These two ships were the prototypes for the mass-produced “Bogue” class CVEs, 45 of which were built from 1942 to 1944.
The first 22 units of the “Bogue” class were conversions of completed or near-complete US Maritime Commission Type C-3 cargo ships; the remaining 23 were built as carriers from the keel up. Long Island and Charger were diesel propelled with a maximum speed of about sixteen knots, which was considered too slow. The “Bogues,” therefore, were given steam turbine propulsion, raising their maximum speed to 18-19 knots. Their full-load displacement was 14,200 tons, overall length was 495 feet, waterline beam was 65 feet, and flight deck length was 440 feet. The internal hanger was served by two flight deck elevators, and the ships were fitted with a single aircraft catapult. Experience with the flush-decked Long Island showed the need for an island bridge and flight control position. Thus Charger was completed with a small starboard-side island and a similar one was adopted for the “Bogues” As completed they were armed with a pair of 5in/51 guns plus ten single 20mm guns as light AA.
Thirty-four of the “Bouge” class were transferred to the RN via Lend-lease, leaving only eleven in USN service. These were joined by the follow-on “Casablanca” class, 50 of which were completed and commissioned from late 1942 to mid-1944—the largest class of aircraft carriers ever constructed. The “Casablancas” were designed from the keel up as carriers, though built to mercantile production standards. They were smaller than the “Bouges” and due to manufacturing bottlenecks, they received reciprocating engines instead of steam turbines, so that their range was less. As completed their armament consisted of one 5in/38 DP, four twin 40mm Bofors AA and twelve single 20mm AA. By 1945, however, both classes had a pair of 5in/38s, eight to ten twin 40mm and up to 27 20mm.
To meet the pressing need for aircraft carriers in 1942, the USN also decided to convert four Type T-3 naval oilers into escort carriers. These ships constituted the “Sangamon” class, and they were considerably larger than the “Bouges” and “Casablancas.” They had a much longer flight deck, a more powerful catapult and, thanks to their oil tanker origins, an exceptionally wide radius of action. The "Sangamons” successfully filled the gap in the Pacific until sufficient CVs and CVLs became available, and they were the prototypes for the final wartime CVEs, the “Commencement Bay” class. These ships were based on the T-3 tanker hull but were built as carriers from the keel up. Thirty-three were ordered but only nineteen were eventually commissioned in the USN, some postwar. The rest were canceled. Those commissioned during the war (late 1944-1945) saw little action before VJ-Day.
In US Navy service, the jeep carriers carried between nineteen and 33 fighters and bombers. In late 1943-early 1944 the “Bogue” and “Casablanca” classes serving in the Atlantic shipped an air group consisting of nine F4F Wildcat fighters and twelve TBF Avenger torpedo bombers; if operating in the Pacific their air group consisted of eighteen F4Fs and twelve TBFs. For the larger “Sangamon” class, the air group consisted of 24 F4Fs and nine TBFs. Later in the war the four “Sangamons” and the follow-on “Commencement Bay” class had air groups consisting of eighteen F6F Hellcat fighters and twelve TBFs. Thanks to their larger hangers and longer flight decks, they were the only CVEs capable of operating the F6F and the Vought F4U Corsair, both of which were considerably larger than the F4F. To speed flight deck operations, the “Sangamons” were refitted with a second catapult and the “Commencement Bays” were completed with two catapults.
Though it was obsolescent as a front-line fighter by 1943, the Wildcat acquired an extended lease on life aboard the jeep carriers. The F4F-4 model with folding wings economized on space in the hanger and could take off from the CVE’s relatively short flight deck without catapult assist. Thus the Wildcat remained in production right to the end of the war. Some 8,000 were produced, nearly 1,000 of which were supplied to Britain’s Royal Navy. The Avenger, which was the largest single-engine aircraft operated by the Navy during the war, required catapult assist for takeoff. Its enclosed weapons bay could accommodate bombs or depth charges in place of a torpedo, and the TBF could also carry air-to-surface rockets underwing. Aboard CVEs in the Atlantic, the Avenger served primarily as an antisubmarine aircraft, while in the Pacific it was also employed aboard CVEs as a light bomber and ground attack aircraft.
The introduction of the CVE revolutionized antisubmarine warfare. For the first time, convoys could be provided with on-the-spot air support. In combination with destroyer escorts, they also formed independent hunter-killer groups. These consisted of a CVE and several escorts, initially older fleet destroyers like the four-piper escort conversions, later the destroyer escorts.
Hunter-killer groups served as convoy escorts and also operated independently, locating and destroying U-boats on passage to and from the Atlantic. This roving hunter-killer concept proved most successful. The ever-present possibility of air attack compelled the U-boats to remain submerged during daylight hours, greatly impeding their operations. If caught on the surface by aircraft from a CVE, they were likely to be damaged or sunk in short order. The hunter-killer group formed around USS Bouge (CVE-9), for example, sank or damaged fifteen German and Japanese submarines between April 1943 and April 1945.
On 4 June 1944, the group formed around USS Guadalcanal (CVE-60) captured U-505. The U-boat was first damaged by depth charges from the destroyer escort USS Chatelain (DE-149) and when she surfaced boarding parties from the escort and the carrier took control of her before she could be scuttled. U-505 was taken in tow by Guadalcanal and brought into port at Bermuda. She was the first enemy vessel captured on the high seas by the USN since 1815 and is now on display at the Museum of Science and Industry, Chicago, Illinois.
In the Pacific, the jeep carriers gave good service in support of amphibious task forces. For this purpose, they formed task groups of two or three escort carrier divisions, each division with four to eight CVEs plus six to eight destroyers and destroyer escorts. These groups escorted the amphibious ships to the invasion era, providing air cover and close air support for troops ashore.
The most famous action fought by the CVEs in this role was the Battle off Samar (25 October 1944), the central action of the larger Battle of Leyte Gulf. A Japanese force of four battleships, six heavy cruisers, two light cruisers and eleven destroyers attempted to close with and destroy the ships of the amphibious task force. In one of the most gallant actions in the annals of the USN, the jeep carriers, destroyers and destroyer escorts of Task Group 77.4 turned back the Japanese attack despite long odds. Task Unit 77.4.3—call sign Taffy Three—bore the brunt. Its three DDs and four DEs closed with the advancing enemy and though heavily outgunned, damaged several Japanese ships with torpedoes and gunfire. The air groups of TG 77.4 attacked as well—this despite the fact that they were armed with depth charges, high-explosive bombs and rockets instead of torpedoes and armor-piercing bombs.
The CVEs of Taffy Three engaged the enemy when he came in range, scoring several hits with their 5in/38 guns. But the price was high: two CVEs were sunk, one by gunfire and one by a Kamikaze, and four others were damaged. Two DDs and a DE of Taffy Three were sunk by gunfire, and twenty-three planes were shot down. In total 1,161 men were killed or listed as missing and 913 were wounded. But the Japanese lost three heavy cruisers and a destroyer, with most other ships damaged, and the battle proved to be the Imperial Japanese Navy's swan song.
The loss of two CVEs at Samar highlights the type's main drawbacks: low speed and vulnerability to gunfire, bomb, and torpedo damage. CVEs were the largest USN warships sunk by Kamikazes in the Pacific; others were sunk by German and Japanese submarines, though only Gambier Bay was lost to surface gunfire. Unlike the fleet and light fleet carriers, which were armored and whose hulls were subdivided to localize damage, the CVEs had only light splinter protection. On the other hand, they could be mass produced in large numbers, many components being prefabricated. Their existence freed the USN's main carrier striking force to act offensively against the enemy and thus the jeep carriers more than proved their worth.
In addition to their combat role the CVEs proved useful as aircraft transports, ferrying replacement aircraft from the US to the front-line forces, both Navy and Army. During the war many Army Air Force planes were given temporary catapult fittings, so that they could fly from the CVEs directly to the end user.
With the war won, most of the jeep carriers were decommissioned in short order and either scrapped or relegated to the Reserve Fleet. All the "Bogues" went to the breakers, and postwar staff studies concluded that the "Casablancas" and "Commencement Bays" were too small to be useful as anything but helicopter carriers. Some of the latter, however, operated Marine Corps air groups during the Korean War, flying the F4U Corsair in the ground attack role.
Other CVEs were converted to operate antisubmarine helicopters and some continued to serve in their secondary role as aircraft transports. USS Thetis Bay (CVE-90) of the "Casablanca" class underwent an extensive conversion to become the USN's prototype helicopter assault ship, pioneering the concept of "vertical envelopment" amphibious operations. As LPH-6 she served in this role from 1955 to 1964.
During World War II the United States produced a total of 120 CVEs, of which 34 were transferred to Britain’s Royal Navy—a testament to the awesome productive capability of the Arsenal of Democracy. Compared to the more glamorous fleet carriers, the CVEs were warships for the working day, manned largely by reservists. Almost all were out of commission by the mid-1960s and none, unfortunately, have been preserved in memory of their service. But the jeep carriers live on in the pages of history, where they more than earned their place.
My brother served on the Iwo Jima (LPH-2). That seems to have been the natural progression from these escort carriers.