LPH-6 Thetis Bay
Other than the LST, the most prominent all-purpose workhorse of the Korean War had been the helicopter. So necessary had these contraptions suddenly become that landing platforms sprouted throughout the fleet and were designed into all possible new construction, while their further implications for amphibious warfare attracted the interest of the Marines. As the tactical possibilities of vertical envelopment were clarified, there came proposals for the conversion of escort carriers to helicopter work and the projection of the helicopter amphibious assault ship (LPH), which would carry a Marine battalion, its supplies, and the helicopters necessary to land it.
By 1951 The type of CVE recommended for conversion to a helicopter carrier had been changed from the previously desired Commencement Bay class to that of the Casablanca class. The Tactics and Techniques Board's report of 05 January 1951 stated: " . . , it had been discovered that the Commencement Bay (CVE-105) class aircraft carrier was being adapted to ASW missions and did not appear to he available for modification. Other class CVEs were in reserve, and as far as the board could determine, there was no immediate requirement for their use. Of these, the Casablanca class (CVE-55) appeared to be the best choice because of its greater speed, in addition to being available in larger numbers. In this light, the hoard 's recommendation was for the Commandant to request the modification of the four carriers of the Casablanca class (CVE-55) or its equivalent."
In a letter to the Commandant on 13 August 1951, the Acting Chief of Naval Operations, Admiral Donald B. "Wu" Duncan, approved the Marine Corps' concept of landing one division by helicopter. He questioned, however, whether the state of development of transport helicopters justified settling, at that time, on a definite method for conducting such operations and beginning a ship conversion or building program. He feared acceptance of the Marine Corps' concept of transporting troops, equipment, stores, and helicopters all in the same ship would automatically require radical changes to existing types of ships or the construction of specially designed new types. Either course would involve a large expenditure of funds. The decision rendered by the Acting CNO was that further experimentation and investigation should be conducted into the matter.
On 12 October 1951, the CNO initiated action to settle the questions raised by the Commandant's concept of future amphibious operations. Although there had been general agreement that in an assault elements of one Marine division would be landed by helicopter, yet to be determined was the type of platform the assault would be launched from. To this end, the CNO directed the Commander in Chief, United States Atlantic Fleet to evaluate the capabilities of transport helicopters and to develop doctrine, techniques and procedures for ship-to-shore movement of helicopter transported troops. Representing the Marine Corps in the conduct of this evaluation was General Graves B . Erskine, Commanding General, Fleet Marine Force, Atlantic, a much-decorated veteran of World War I and a pioneer in the development of amphibious warfare doctrine. In the early years of World War II he had been Chief of Staff, V Amphibious Corps and later commanded the 3d Marine Division on Iwo Jima.
To develop the assault helicopter concept in FMFLant, on 20 December 1951 General Erskine convened a board with Major General Field Harris, the Commanding General, Aircraft, FMFLant as the senior member. General Harris' board met on 2 January 1952 and decided that the best method for obtaining a solution to the problem was to hold a series of ship-to-shore exercises during the early part of the year. As a result, HELEX I and II took place between 20 January and 28 February 1952. Participating in both exercises were the newly formed helicopter squadrons HMR-261 and -262. Operating from the deck of the USS Siboney (CVE-122), the two squadrons lifted troops of the 1st Battalion, 8th Marines into landing zones at Camp Lejeune. In addition, the squadrons airlifted their own personnel and equipment ashore after the tactical portion of the exercise had been completed.
General Harris' board made two major determinations from the results of HELEX I and II. The first conclusion was that the CVE-105 class carrier could adequately handle aircraft, personnel, and logistically support a vertical envelopment from the sea. Secondly, the board evaluated the employment of a mix of two different types of ships, i.e., a helicopter transport and a troop transport with a helicopter deck, and concluded that such combination of ships was tactically unsound. The factors militating against the use of separate ships were found in the limited troop-carrying capacity of the HRS and the additional time required for the aircraft to land, load with troops, and relaunch from the troop transport.
When he assumed the Commandancy on 01 January 1952, General Lemuel C. Shepherd, Jr., who relieved General Cates, touched in his inaugural address on the successes achieved by the helicopter and the role it played in the Korean War when he said: "Seven years have passed since the development of the helicopter as a troop carrier was begun, but in the fall of 1951, in the bleak Korean countryside, the worth of the ungainly looking craft was finally proved. Just as the amphibian tractor came to the fore as a troop carrier over the reefs of Pacific atolls during World War II, so the helicopter became the greatest single innovation during the Korean conflict as a tactical and humanitarian medium of transportation . . . ."
On 5 March 1952, shortly after the termination of HELEX I and II, General Cates requested that General Erskine make additional recommendation on three related items which could be derived from the recent tests. Two of the subjects had not been addressed in prior reports but the third had been treated by the Tactics and Techniques Board in February 1951. The three areas to be considered were: 1. The suitability of the CVE class carrier and any modifications necessary to make it more suitable for assault helicopter operations; 2. The general characteristics required for a helicopter transport vessel for future construction; 3. Based upon 1 . and 2 . above, the shipping requirements to support helicopter operations involving the assault elements of one Marine division.
General Harris' board responded to the Commandant's request on 29 March 1952. It determined that the CVE-55 class carrier, with a few modifications, appeared to be suitable for assault helicopter operations with the HRS. For operations with the HR2S, additional modifications would be necessary. In this connection it was recommended that a design study be conducted in order to determine the extent of the alterations needed to make the ship compatible for HR2S operations. No determination was made on the second objective as the board believed that additional helicopter assault exercises should be held prior to settling on the general characteristics for such a ship.
The estimated shipping requirements for transporting the assault elements of one Marine division (12,000 to 14,000 troops and related helicopter personnel) were given as 20 CVE-55s if the HRS was the only type helicopter used. If the HR2S was to be employed in lieu of the HRS, then 13 CVEs would be necessary. However, as an immediate course of action, since there were not enough HRSs available to land the divisional assault elements, General Harris recommended that only four CVE-55s be modified for helicopter operations and suggested that only a minimum modification be accomplished. In any case each ship should be modified to accommodate at least 20 HRSs, 850 troops, and 75 tons of supplies.
General Harris' report was forwarded through appropriate headquarters to the CNO. General Cates concurred with the recommendations and stated in his endorsement on 28 April 1952 that modification of four CVE-55 class aircraft carriers was considered satisfactory as an inaugural step in implementing the development of the helicopter assault capability. He mentioned that additional conversions would be necessary at an early date to fill the desired requirements. General Cates concluded by stating that the ship modification measures "are viewed as essential in maintaining the momentum of the helicopter program [and] to insure early availability of a Fleet Marine Force helicopter assault capability in connection with fleet amphibious operations."
Following the Commandant's request, the CNO, on 8 September 1952, directed the Chief, Bureau of Ships, to undertake a study to determine the feasibility of modifying a CVE-55 class aircraft carrier. Two months later, the CNO was advised by BuShips that the feasibility study had been completed and the CVE-55 class appeared to be an excellent ship for such use and the suggested conversion to rotory-wing operation was recommended to permit service evaluation.
Unfortunately, by the time BuShips had completed the study it was too late to have the modification included in the 1954 Fiscal Year budget. To ensure incorporation of the four Landing Platforms for Helicopters (LPHs) in the 1955 budget, the Commandant, on 26 November, repeated his request for the conversions of the CVE-55s. Soon thereafter, on 5 February 1953, General Cates revised his shipping requirements. He informed the CNO that the Marine Corps now had a specific need for a total of 16 LPHs instead of 12; four modified CVE-105s and 12 CVE-55s. These requirements were taken from a study completed earlier by the Tactics and Techniques Board at Quantico. The 16 helicopter aircraft carriers were the minimum number of ships which the Tactics and Techniques Board felt could accommodate the assault elements of one Marine division.
In May 1955, Thetis Bay was towed to the San Francisco Naval Shipyard where she began conversion to the Navy's first assault helicopter aircraft carrier. On 1 July 1955, her designation was changed from CVE-90 to CVHA-1. With that change, she became a complement to the attack transport. Her helicopters supplemented landing craft to give the Navy and Marine Corps the flexibility of a vertical assault capability. The CVHA-1 had an overall length of 512 feet, a beam of 108 feet, a displacement of 11,000 tons full load, and a maximum speed of 19 1/2 knots. Approximately 1,000 combat troops and 20 HRS helicopters could be accommodated.
The first results of the Commandant's request for LPHs in early 1953 were realized on 20 July 1956 when the USS Thetis Bay (CVE-90) was commissioned after undergoing a conversion in the San Francisco Naval Shipyard. Redesignated as the CVHA-1 (Assault Helicopter Aircraft Carrier), the Thetis Bay was designed to afford the Marine Corps the opportunity to evaluate the vertical assault concept. Although it was not intended that the converted ship be the prototype for future LPH (CVE) conversions, it did provide the Marine Corps with the opportunity to evaluate some features desirable in new construction.
The Fiscal Year 1955 The Fiscal Year 1955 budget called for two such conversions, but due to monetary shortage the second CVHA, the USS Block Island (CVE-106), was not started until January 1958. The conversion of the Block Island was never completed though, mainly as the result of an austerity move. The USS Thetis Bay, the first of these conversions, had had a checkered career. A product of the Kaiser shipyards in Vancouver, Washington, which had gained fame in World War II as a mass producer of ships, she was not one of those more rapidly rushed to completion. Kaiser received the contract for her on 18 June 1942 but did not lay the keel until three days before Christmas the next year. The ship was launched 16 April 1944 and commissioned five days later. After short service in World War II she went into mothballs along with much of the rest of the fleet. Initially designated simply Maritime Commission Hull No. 1127 (while under construction), she sailed in World War II as CVE-90, an escort carrier; and after conversion to a helicopter assault ship became for a short time CVAH-1 (carrier, assault, helicopter) and finally LPH 6.
The conversion started in the San Francisco Naval Shipyard 1 June 1955 and was finished 1 September 1956. In an unusual event, the vessel was recommissioned prior to the completion of the work. Captain Thomas W. South II ran up his flag on 20 July 1956 as the commanding officer of the first - and at this time - only ship specifically adapted to conduct helicopter assault operations. Captain South had close association with both aviation and the Marine Corps. The son of Marine Colonel Hamilton D. South, Captain South had flown in the Pacific during World War II and had commanded an experimental unit equipped with remote-controlled assault drones. Captain South, who eventually attained the rank of Rear Admiral, had a brother, Colonel Hamilton D. South, who was a Marine flier and later Director of Information at HQMC.
To the Marine Corps, the Thetis Bay constituted visible proof that amphibious vertical assaults could be conducted, but compared to other warships of the time, she was not impressive. At maximum load she displaced only 10,866 tons. Modern attack aircraft carriers were being launched at the same time that displaced 56,000 tons, and it would not be long before ship engineers started designing carriers that would displace over 85,000 tons. Thetis Bay's overall length of 501 feet was slightly less than half that of the new attack aircraft carriers, and the conversion's flight deck did not extend the entire length of the ship. Yet this small LPH would have to operate with the HR2S which was 88 feet long as it lifted off with the assault troops. The ship could accommodate 103 Marine officers (including the helicopter pilots) and 901 enlisted men in addition to the 40 officers and 598 men required to operate her. Her two boilers and double propellors could drive this small ship through the water at 19 knots.
Less than a month after the conversion was complete, on 24 September 1956, Colonel Frederick R. Payne had the distinction of being the first Marine helicopter pilot ever to land on an actual LPH when he brought his HRS-3 helicopter down on the flight deck and was eagerly greeted by Captain South. This ship was always known to pilots and Marines who operated from her as the "Teddy Bear," from her identifying call sign on the radio. The nickname became almost a term of affection among the early pilots operating from her decks rather than any comment on her size.
In retrospect, the Thetis Bay seems pathetically small. At that time, however, she was the forerunner of all that would come after her. She would serve long after, serve well, and serve courageously. By late 1958, the Marine Corps had gained valuable operational experience with the Thetis Bay and the Commandant had determined that the best solution for meeting assault helicopter aircraft carrier requirements was through new construction or by modifying other type World War II carriers.
On 28 May 1959, Thetis Bay's designation was changed to LPH-6, amphibious assault ship. In May 1960, Thetis Bay participated in a practice night assault landing at Camp Pendleton during which her helicopters carried 1,300 troops and 33 tons of cargo to the objective area. This was the first large-scale night landing of ground forces by carrier-based helicopters.
Thetis Bay stood out of Norfolk on 5 January 1964 en route to Philadelphia for inactivation and arrived there the next day. She was decommissioned and struck from the Navy list on 1 March 1964. Her hulk was sold in December 1964 to Peck Iron & Metal Co., Inc., Portsmouth, Va., for scrap.
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