USN Carrier Evolution IX: Escort Carriers

Ninth article in a series by Scot MacDonald. Reprinted with permission: Naval Aviation News, December 1962 pp 49-53.

“The story of the escort aircraft carriers is like a story with a surprise ending. When the United States began to build them, there was a definite purpose in view—fighting off submarines and escorting convoys. But as the war progressed, the small carrier demonstrated surprising versatility. It became a great deal more than its name implies. From a purely defensive measure, the escort carrier emerged as an offensive weapon.”—FADM Chester W. Nimitz, USN, CinCPacFlt/CinCPOA, 1945.

Toward the end of World War I, Great Britain experimented in converting light cruisers to aircraft carriers—notably in HMS Cavendish, of 32 knots and about 10,000 tons displacement. But with the signing of the Armistice, the project was abandoned. Despite this, it was a subject of interest in the following years.

Where it all began: HMS Vindictive (ex-Cavendish) was laid down as a Hawkins class cruiser and converted to an aircraft carrier, carrying 12 aircraft, in June 1918. The flight decks were removed and the ship reconfigured back to a cruiser in 1924.

Cruiser conversion considered in 1925

In 1925, the General Board seriously considered the conversion of cruiser hulls to aircraft carriers. Although treaty limitations restricted the building up of carrier strength, there was sufficient uncommitted construction tonnage to permit the building of more carriers than the U.S. Fleet had. Could this uncommitted tonnage be best employed in building small carriers? The Board’s answer can best be summed up in this excerpt from its report:

Incomplete studies of the subject by the Bureau of Construction and Repair and the meagre information available concerning the performance of airplanes from carriers of approximately 10,000 tons displacement does not justify building them at this time.

1927 analysis

But the subject of “light” carriers was of recurrent interest to the U.S. Fleet. In May 1927, LCDR Bruce G. Leighton prepared a paper in which he analysed the problem. He titled it: Light aircraft carriers: A study of their possible uses in so-called “cruiser operations,” comparison with light cruisers as fleet units.

Though the title may have been cumbersome, the document was impressive. He forecast every fundamental combat requirement of the latter-day CVLs and CVEs, including the bombing of capital ships, support of fleet operations, anti-submarine work, scouting and reconnaissance, and the reduction of enemy shore bases. He concluded that “all things considered, it might well be considered as a worthy substitute for the light cruiser, or even distinctly preferable to the cruiser.”

John S. McCain Sr

For the next dozen years, the subject interjected itself spasmodically and unsuccessfully into Navy thinking. But in March 1939, CAPT (later ADML) John S. McCain Sr, then commanding the Ranger, wrote to the Secretary of the Navy advocating the building of at least eight “pocket-size” carriers of cruiser speed. These were not meant to replace the CVs, but to supplement them, giving force commanders much more flexibility in the use of ship-based aircraft at sea, without jeopardising the much more costly heavy carriers. RADM (later FADM) Ernest J. King, in his endorsement to the letter, was not at all enthusiastic about this scheme. He suggested that existing aircraft carriers carry the maximum number of planes permissible as a better solution than the construction of smaller carriers.

The matter was not entirely dropped, however, for the Bureau of Construction and Repair was considering and even drawing plans for the conversion of 20- or 21-knot passenger ships, creating experimental carriers with short flight decks. By November 1940, the Chief of Naval Operations brought these considerations to an abrupt halt, basing his decision on a letter from SecNav to the Chairman of the U.S. Maritime Commission. SecNav wrote:

The characteristics of aircraft have changed, placing more exacting demands upon the carrier. These demands are such that a converted merchant vessel will no longer make as satisfactory an aircraft carrier as was the case when the plans for those vessels were being drawn.

Presidential influence

In commenting on the beginning of escort carriers, historian LEUT William G. Land, USNR in Functional development of the small carrier (CVE) says, “The escort carrier was forced upon the Navy by the President.”

Indeed, President Franklin D. Roosevelt did actively enter the “light” carrier controversy. Great Britain had been at war with Germany since September 1939. Since that time and before the U.S. entered the war, large numbers of U.S.-built military aircraft were sold to the British. The U.S. had need for an aircraft-carrying ship to speed delivery. By mid-February 1941, RADM W. F. Halsey (later FADM) had written to Commander-in-Chief , U.S. Fleet:

A previously stated expectation, that the Navy would be called upon to provide transport for Army aircraft, has now materialised in the current diversion of Enterprise and Lexington to transport 80 pursuit planes from the West Coast to Hawaii. To continue with primary reliance on aircraft carriers for such work, as is our present necessity, seriously endangers the availability of air-offensive power in the Fleet.

ADML Husband E. Kimmel, in endorsing this letter from his Commander Aircraft Battle Force to the Chief of Naval Operations, fully concurred and pointed out that on five separate occasions in the past he had himself urged such action.

Helicopter carrier?

Earlier, on 21 October 1940, CNO had received a memorandum from the President’s Naval Aide advising him that President Roosevelt proposed the Navy acquire a merchant ship and convert it to an aircraft carrier, accommodating eight to twelve helicopters (not yet operated by the Navy) or aircraft capable of landing or taking off in a small space. The purpose of this type carrier was to “provide quick conversions for carrying small planes which could hover ahead of convoys, detect submarines and drop smoke bombs to indicate their locations to an attacking surface escort craft.”

HMS Tracker, an escort carrier with 816 Squadron Swordfish embarked.

CNO decided on the last day of 1940 that the Chairman of the Maritime Commission would be consulted to determine the availability of ships for this purpose. On January 2nd, it was found that two Danish ships might permit conversion, but later investigation proved this would not be possible.

Standardisation

The results of this January 2 conference determined that the two ships (one was to be sold to Great Britain ) selected:

Should be of the same or very similar design in order that the plans made for one could be applicable to both; that the airplanes should be further investigated to determine the type and availability; that an armament of four AA pom-poms and one five-inch surface gun should be such as to insure stability at all stages of loading.

These converted merchant ships were to fill the need later expressed by (then) ADML Halsey, the transport of aircraft, as well as to provide protection to Allied convoys.
On 6 January 1941, ADML Harold R. Stark, CNO , convened a conference in his Washington office to discuss merchant-conversion. The autogyro type aircraft was considered of dubious usefulness because of its inability to carry any load other than smoke bombs; an aircraft, to meet the purpose designed, must have some offensive characteristics. An abbreviated deck was ruled out. The converted ship should be diesel-driven in order to eliminate smokestacks. The decision was made to obtain from the Maritime Commission, if possible, C-3 cargo ships.

Two diesel C-3s

On the following day, CNO was informed that two diesel-driven C-3 type ships, the Mormacmail and the Mormacland, would be suitable for conversion and were available. He was told by President Roosevelt that any plan that would take more than about three months to complete conversion would be unacceptable. This, in effect, placed pressure on the project. The idea of substituting “blimps” for autogyros or heavier-than-air craft was flirted with but, by January 15, was “out of the picture.” The Mormacmail was acquired on 6 March 1941. On June 2—just within the three-month limitation set by the President—she emerged from conversion and was placed in commission as the aircraft escort vessel USS Long Island (AVG-1), commanded by CMDR Donald B. Duncan who, on 31 December 1942, was to become the first commanding officer of USS Essex.

Early plans for the conversion called for the installation of a 305-foot (93 metres) flight deck on the Mormacmail, but the Bureau of Aeronautics required at least 350 feet (106.6 metres) to safely land SOC Seagulls aboard. Upon commissioning, Long Island had a deck length of 362 feet (110.6 metres). She had one elevator, handled 16 planes, had a trial run speed of 17.6 knots and berthed 190 officers and 780 men.

The Mormacland, acquired at the same time, was similarly converted and was turned over to the British as HMS Archer (BAVG-1) when it was completed the following November. Experience with the BAVG and the two British conversions led the British to believe that the diesel-driven ships were too slow for their purpose as special escort vessels—although they were no slower than the later Bogue carriers.

(Ed. note: The British also found some early diesel propulsion units seriously unreliable. For instance, despite major dockyard repairs in 1943, the diesel-driven HMS Archer was reduced to stores and maintenance duties after completing only two missions.)

Training and trials ship

Long Island was used primarily as a training ship during the remaining peacetime months of 1941. She was subjected to tests and experiments—much the way USS Langley had been in her early days—to obtain data needed for the construction of later escort carriers. As a result of the Navy’s experiences with this ship, other CVEs were outfitted with two elevators instead of one, the flight decks were lengthened, and the anti-aircraft power was increased.

On 26 December 1941, SecNav approved the conversion of 24 merchant hulls for the 1942 shipbuilding program and, in March, ordered the conversion of cruiser hulls, which became the CVLs. LCDR Leighton’s 1927 paper was proving its farsightedness.

Naval aviation historian Henry Dater traced the next developments in a paper published in Military Affairs:

There were only 20 C-3 hulls available for conversion, ten of which were earmarked for the Royal Navy and ten for the United States .  
The new ships were improved by the substitution of a steam turbine power plant for the diesel engines employed in the Long Island and Charger (the latter was redesignated CVE-30 and replaced CVE-1 as a training ship when the Long Island was pressed into service, ferrying planes and pilots at the outbreak of war), and by the addition of a slightly larger flight deck (436 x 79 feet; 133 x 24 metres), a small island, and a considerably larger hangar space.
They were referred to either as the CVE-6 class, from the numerical designation of HMS Battler, or as the Bogue class, from the first ship to operate with the U.S. Navy.
The remaining four CVEs authorised for the 1942 program were converted from Cimarron class fast fleet oilers and were known as the Sangamon (CVE-26) class. These were considerably larger, having a flight deck of 503 feet by 85 feet (153 x 26 metres), and were able to accommodate two small squadrons of aircraft. Because of their size, work was rushed on them during the summer of 1942 so that they would be available for the North African invasion in the autumn.

Easy pickings

Before the U.S. entered the war, German U-boats hovered near British coastal ports and picked off merchant ships with ease. Land-based RAF planes drove the German submarines further out to sea. To make matters more difficult for the enemy, convoys sailed closer together, opening up larger areas of the North Atlantic for the German subs to search. The Germans solved this problem by developing the “wolf pack” technique of operating in groups, then concentrating for the kill when convoys were sighted.

Henry Dater wrote:

It was this technique which created the British desire for aircraft escort vessels in late 1940 and 1941. With the entry of the United States into the conflict the Germans found easy pickings off the American coast, but it was only a matter of time until land-based air on this side of the Atlantic drove them out to sea once more. There, in mid-ocean, was a vast area in which the convoys did not have the assistance of aircraft. By early 1943 it became evident that the decisive campaign was to be fought in that area.

Not highly regarded for their steady deck properties, The CVEs were allotted the “will roll on damp grass” category by pilots.

Escort procedures

The air officer of the Bogue described escort procedures during March and April 1943:

The ship was stationed inside the convoy for this work. The convoys were in columns of five ships each with about 700 yards between columns.
They left a double space in the middle in the centre of which they placed the Bogue. The other escorts were placed around the convoy in a half circle. The idea was, if possible, to use our catapults and to stay in our centre position when launching our planes so there wouldn’t be any wide separation. As it happened, we had westerly winds on the east-bound convoy so we had to turn around to launch planes and to take them aboard. Consequently, the separation was fairly large due to the fact that it was what is called a high speed convoy, “nine knots!”

Hunter-killer tactics

Though this tactic met with considerable success at first, it was primarily defensive. A new technique was found more effective. A small task group took up a position where it could throw its support to either of two convoys in a general area. Escort carrier-based aircraft scouted ahead, searching out German U-boats before the submarines could make contact. This permitted the carriers to be released from the difficult manoeuvre necessary in the central slot of the convoy. Out of this technique emerged the successful hunter-killer tactic that eventually freed Allied shipping in the North Atlantic.

The Sangamon class escort carriers, built as fleet oilers under the Merchant Marine Act of 1936, were completed in 1939, but in the 1942 shipbuilding program were slated for reconfiguration as aircraft carriers. Only four hulls were on hand. “Had more oiler hulls been available,” wrote LEUT Land, “they would have become the prototype of the small carrier for the ensuing year’s program. But the overwhelming need for fleet oilers—to make possible our logistic advance—prevented this type of hull from being again used for carriers, until 1944.”

Launched as the Esso Trenton on 4 November 1939 and purchased by the USN 22 October 1940, USS Sangamon (AO-28) served initially as a tanker (top). One of the largest USN escort carriers, she was the lead in a four-ship class and completed her conversion (ACV-26, later CVE-26) on 20 August 1942 (middle). Sangamon was damaged by a kamikaze in a night attack, 4 May 1945 (bottom). With all bridge communications and all aircraft but one destroyed, that aircraft became her only means of radio communication with the fleet. Sangamon returned to Norfolk for repairs that were halted by Japan’s surrender.

Sangamon dimensions

The Sangamons had an over-all length of 553 feet (168.6 metres), a speed of 18.3 knots, a trial displacement of 23,235 tons, and carried 120 officers and 960 men. They were armed with two five-inch, 38 calibre guns, two quad and ten twin 40mm AA mounts. They were equipped with two hydraulic catapults forward.

Historian Land wrote:

With the CVs, except Ranger, being employed in the Pacific, planning for the North African landings depended on the completion of the AO conversions of Suwannee, Sangamon, Chenango and Santee. For this reason, Suwannee had to cut down on its pre-commissioning period, fitting out and shakedown in order to be substituted in the final plans for the much smaller Charger, the ex-BAVG that had been doing regular duty as qualification carrier in Chesapeake Bay. Santee, likewise, was barely completed in its essentials and had had hardly any exercise with its air group before its first combat operation was to begin.

CAPT William D. Sample, commanding Santee, wrote of the hectic early days aboard:

Santee left Norfolk Navy Yard 13 September 1942 with yard workmen still on board and her decks piled high with stores. During that first month, Santee returned to the yard twice and was never free of the yard workmen. The completion of the ship continued while the fitting out and shake-down were proceeding together. At the end of the month, the air group had operated aboard only a day and a half and guns had been fired only for structural tests…The Navy Yard had done an almost impossible task in getting the ship out in time for the pending operations but, in so doing, only the essentials had been completed, and it was then necessary for the ship to install, adjust, calibrate and repair until the ship could use her battery and equipment…The service experience necessary to test many of the questionable features of the ship’s design was soon obtained in a wintry gale encountered en route to Bermuda. The two forward boats were carried away, the new upper decks proved to be sieves and the repair work of the ship’s force got underway in earnest.

The first of a pair of USAAF P-40 Warhawks catapults from USS Chenango to explore Port Lyautey runway serviceability in support of the Casablanca landings. The P-40s had no hook and once airborne were forced to land somewhere solid, other than the aircraft carrier from which they launched. The Port Lyautey airfield had been very effectively bombed by USN aircraft and both aircraft crashed while attempting to land between the bomb craters. Despite futile efforts to stop them, 85 more Chenango P-40s arrived overhead some 45 minutes later. Of these, 20 were destroyed attempting to land.

Aircraft ferry

The carrier Chenango was used, in the North African operation that followed, as a ferry carrier for Army P-40s on the outward trip, as a fuel supply ship while moored at Casablanca, and as a fleet escort, with a borrowed air group furnishing air cover, on the return trip. Her sister ships, however, launched TBF-1 Avengers, SBD-3 Dauntless and F4F-4 Wildcat aircraft in support of landing operations for the capture of Casablanca and Port Lyautey. They were units of Task Force 34.

As part of the Northern Attack Group, Sangamon and Chenango assisted troops landing at Mehedia, not far from Port Lyautey (now Kenitra). Ranger and Suwanee provided air cover for the Centre Attack Group at Fedhala, northeast of Casablanca. Santee was the only carrier assigned to the Southern Attack Group, providing combat air patrol and anti-submarine patrol for the landing force at Safi —the only port in Morocco, other than Casablanca, that would permit the landing of 28-ton General Sherman tanks. It was for the capture of Casablanca that these tanks were needed.
Between 8-11 November 1942, Suwanee launched 255 combat sorties; Santee, 144, and Sangamon, 183.

Neutralise airfield citadel

During Sangamon ’s participation in the Northern Attack Group operation, her planes were called upon to neutralise a kasbah or citadel that guarded the Port Lyautey airdrome. Several SBDs delivered bombs on target. “The garrison then,” wrote Samuel Eliot Morison, “came out with their hands up and our infantry walked in.” By November 15, Sangamon’s part in the invasion of North Africa was completed and she sailed for Hampton Roads.

Planes in the Suwanee joined those based in the Ranger in bombing missions during the Battle of Casablanca. The Suwanee, like the Santee at Safi, encountered light winds. Many landings were made aboard with only 22-knot winds across the deck.

Despite the greenness of the crews in escort carriers, generally, they gave a good account of themselves, according to CinCLant:

The CVEs proved to be a valuable addition to the Fleet. They can handle a potent air group and, while their speed is insufficient, they can operate under most weather conditions and are very useful ships.

Their missions in the invasion of North Africa completed, Sangamon, Chenango, and Suwanee were dispatched to the Pacific. By the end of 1942, U.S. carrier strength in the Pacific had been reduced to the Enterprise and the Saratoga.

Mass production

In the meantime, President Roosevelt announced a need for more escort carriers. Shipbuilder Henry J. Kaiser had impressed the President with the merits of a plan which would permit the mass production of escort carriers, under a program to be supervised by the Maritime Commission.

The first of these, USS Casablanca (CVE-55), was commissioned 8 July 1943, and gave its name to the class—CVE-55 through CVE-104. They were also referred to as Kaiser class escort carriers. The Kaiser yard completed its 50-ship program on 8 July 1944. This was an impressive achievement in a wartime production program.

Dimensions

The Casablanca class had an overall length of 512 feet, 3 inches (156.1 metres), a speed of 19.3 knots, a trial displacement of 9570 tons, and carried 110 officers and 750 men. They had one five-inch (127 mm), 38 calibre gun and eight twin 40 mm AA mounts. The aircraft complement consisted of 12 Grumman Avenger TBMs and 16 Grumman (General Motors-built) Wildcat FM-2s; on the flight deck was a single hydraulic catapult, forward. Final details were worked out for a new class escort carrier during the trials of the Sangamon and Santee and during the planning for the 1944 building program. These ships were the first Navy-designed escort carriers for which hull and propeller model tests were carried out at the David W.Taylor Basin. The design was formally approved by CNO on 10 December 1942 and the contract was let on 23 January 1943.

The first of these carriers was the Commencement Bay (CVE-105) from which the class got its name. It had an overall length of 557 feet (169.8 metres), a speed of 19 knots, and a trial displacement of 23,100 tons. Few of these ships saw action in the war—the Commencement Bay was commissioned in November 1944. Only nine others were commissioned before V-J Day the following August. They incorporated all lessons learned since the Long Island was commissioned.

As the escort carriers gained experience, they earned the respect of the Fleet by proving themselves versatile in anti-submarine warfare. The Sangamon class first demonstrated combat capability in the support of the North African invasion. The first major carrier-supported amphibious landing in the Pacific was the capture of the Gilberts and Marshalls. Eight escort carriers participated, two of the Bogue class, three of the Sangamon class, and three of the Casablanca class. The changing status of these vessels is reflected in their redesignation. Originally identified as aircraft escort vessels (AVGs), they were redesignated on 20 August 1942, as auxiliary aircraft carriers (ACVs, and finally, on 15 July 1943, a directive changed the escort carrier symbol to CVE, reclassifying them as combatant ships.

Effectiveness

At the end of the North African invasion, CAPT (later VADM) Calvin T. Durgin evaluated the effectiveness of the escort carriers when he presented his report:

Due to their low speed, lack of protection and light armament, it is considered hazardous to employ a CVE group in operation where there is likely to be an effective enemy opposition. Such a group can, however, be used to advantage, and is capable of inflicting substantial damage to the enemy in assault where the enemy air and sea opposition is negligible or when it is being contained by other superior forces. When this situation exists, the CVE is well equipped to provide all support until landing strips are established ashore, and it can be effectively employed for bombardment spotting, combat air patrols over beaches and surface forces, for all forms of air reconnaissance missions and for bombing, rocket and strafing attacks.

The establishment of this force was made possible by the increasing number of carriers—notably of escort design—made available to the Fleet. Experience at Palau and Morotai and the difficulties encountered later at Leyte all pointed to the need for better planning in advance of operations if the CVEs were to perform efficiently their enlarged responsibilities. RADM Durgin’s command held administrative control over all escort carriers operating in the Pacific, except those assigned to training and transport duty.

On 15 December 1944, the escort carriers provided direct support for landings on Mindoro, and in the assault area on the next two days. Between 3-22 January 1945, 17 escort carriers covered the approach of the Luzon Attack Force against serious enemy air opposition from kamikaze pilots. This force of ships, Task Group 77.4, conducted preliminary strikes in the assault area, covered the landings in Lingayen Gulf , and supported the inland advance of troops ashore. In 1945 the CVEs saw a great deal of action. On the last three days of January, six escort carriers under RADM Sample (as CAPT, first C.O. of Santee) provided air cover and support for landings by Army troops at San Antonio near Subic Bay, and at two other nearby Philippine beaches.

Iwo Jima

In February, RADM Durgin directed his carriers in the battle for the capture of Iwo Jima. In March, the Okinawa campaign began, the last, and, for naval forces, the most violent major amphibious campaign of World War II. As Task Group 52.1, RADM Durgin, with an original strength of 18 escort carriers, conducted pre-assault strikes and supported the occupation of Kerama Retto, joined in the pre-assault strikes on Okinawa, and, from a fairly restricted operating area south-east of the island, supported the landings and flew daily close support for operations ashore until the island was secure on June 21.

The U.S. suffered few losses to the enemy in these ships. Five carriers of the Casablanca class were lost in the Pacific; one Bogue class was torpedoed in the Atlantic. During the war years, 76 CVEs of various classes were commissioned, in addition to the Long Island, commissioned months earlier. Seven more Commencement Bay class were commissioned during the post-war years. During the war, four sister ships to Long Island were transferred to the British, as were 34 additional escort carriers of the Bogue class. Four were sunk; at the end of the war, the rest were returned to the U.S. from Lend-Lease and were either sold or placed in the reserve fleet.

ASW victories

Through fulfilling a basic need of transporting large numbers of assembled aircraft to various theatres of war, the quickly conceived and executed escort carrier developed into an anti-submarine warfare weapon that defeated the German U-boat threat in the North Atlantic. They provided combat capability in the support of fleet operations in both the Atlantic and the Pacific. In short, they displayed a versatility, proved under the pressures and urgencies of a war that engulfed the world.