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Amphibious Assault Ships

After the disappointing performance of the auto-gyro during the 1930s, Marine Corps interest in rotary-winged aircraft was not fully revived until 1943. During that year Marine officers from Division of Aviation (DivAvn), Headquarters Marine Corps (HQMC) sat as members of a joint Navy-Coast Guard-Marine Corps board to discuss formation of a program for the use of Sikorsky R-4 and R-6 helicopters. It was not until June 1946, however, that the first official action to institute a Marine Corps helicopter program began when General Alexander A. Vandegrift, Commandant of the Marine Corps (CMC), established a billet for one officer and three enlisted men within his headquarters.

The first two Sikorsky H03S-ls arrived from VX-3 to the newly formed Marine Helicopter Squadron One at Quantico until 9 February 1948. February 9, 1948 marked the delivery of the first helicopters to the Marine Corps and that delivery changed the face of the Corps forever. The development of the helicopter coupled with that of the amphibian tractor is what made the Marine Corps what it is today. Helicopters gave Marines the capability for air mobility and assault from the sea. Ever since their introduction to the Marine Corps, helicopters have played an invaluable role in the mission of the Corps.

The Casablanca Class CVE (Thetis Bay, CVE-90) had a displacement of 7,800 tons and a length of 512 feet, and the Independence Class CVL (Monterey, CVL-26) had a displacement of 11,000 tons and a length of 622 feet. The big obstacle to operating helicopters from these ships rested in the limitations imposed by CVE and CVL elevators and hangar deck dimensions and modification of CVE-CVL types to handle a helicopter carrying 20 combat troop and 5,000 pound such an aircraft is considered to be a project of major proportions. As of 1947 the actual construction of such a helicoptere could not be reasonably expected prior to 1951 and the imposition of the CVE-CVL restrictions would make the meeting of the minimum requirements of the Marine Corps very doubtful. Until the type of aircraft carrier to be used for helicopter operations was officially determined, further work on a design study which had begun in April in the Bureau of Aeronautics was stopped.

The DCNO (Operations), Vice Admiral Forrest P. Sherman, recommended on 6 May 1947 that a two-step study be undertaken to determine exactly which size helicopter should initially be designed for the Marine Corps. Admiral Sherman gave no assurance that a larger type aircraft carrier than a CVE or CVL could be assigned for an amphibious operation employing helicopters as one of the assault elements; therefore, he recommended that the DCNO (Air) investigate the practicability of alterations to hangars and elevators of either CVE or CVL types to handle the helicopter of 5,000 pounds capacity. If this appeared possible without excessive cost and loss of other characteristics of the type, he said called for proceeding with the design and procurement of the 5,000 pound capacity helicopter.

By 03 June 1947, Admiral Duncan had concluded these studies. "It appears that the 5,000 pound helicopter would be of such dimensions both in length and height as to preclude modifying the CVE or CVL carriers except at exorbitant cost." Admiral Duncan continued "By overlapping the rotors in future designs it appears possible to . . . permit stowage of a 3,500 pound helicopter in the CVE-CVL class carriers without modification of the ship or elevators . . . . [therefore] the Chief of the Bureau of Aeronautics is being requested to obtain design proposals for a 3,500 pound payload helicopter.

A memorandum dated 3 June 1947 to the Assistant Chief of Naval Operations (Marine Aviation), (ACN O(Marine Aviation)), Major General Field Harris, recommended that the Commandant eliminate the stowage requirements for the assault helicopter as it imposed many undesirable design factors - the most pertinent one being "that a rotor overlap of approximately 75 percent to 80 percent would be necessary in order to meet the elevator dimensions."

The only helicopter closely meeting that criteria at the time was the small Piasecki XHJP-1 which was still in the design stage and, in addition, had a useful load of only 1,024 pounds, almost 4,000 pounds less than the required minimum. The Military Requirements Section memorandum further mentioned that rotor overlap of such magnitude imposed "a heavy unknown factor on the design." The requirement for the helicopter to be serviced (stowed, repaired, and checked) on the hangar deck of a carrier imposed the undesirable design factor thereby jeopardizing the success of entire proposal. In order to meet the optimum requirement for a 5,000-pound payload the memorandum mentioned flight deck servicing should be accepted in lieu of hangar deck "and many marginal design factors and difficult design limitations would be eliminated."

On 09 July 1947 the Commandant made an important change relating to the helicopter's characteristics by specifying only one size helicopter of a 5,000-pound minimum payload capability. It eliminated the requirement for the helicopter to be accommodated by the ship's elevator and stowed on the hangar deck and listed the overall dimensions as "small as possible." The design proposal for a 3,500-pound helicopter was cancelled. In order that the early landing may he provided with necessary continuity, it is necessary that communications vehicles, recoilless weapons, and initial resupply he provided at an early hour and, ideally, that these should be followed by artillery. This required a payload of approximately 5,000 pounds.

The Marine Corps Schools (MCS) amphibious command post exercises were held annually by joint Navy and Marine Corps forces to simulate a ship-to-shore assault landing against an enemy-defended beach. Operation PACKARD II represented an ideal opportunity for HMX-1 to implement one of the helicopter program objectives for 1948 and woul d present the first test in the movement of troops by helicopters in a ship-to-shore operation. For problem purposes, the regimental staff planned in full, and theoretically executed, the ship-to-shore movement of a constructive regimental combat team using a problem force of 250 HRP-1 helicopters operating from four CVEs . This movement and subsequent employment of the helicopter-borne force was part of, and integrated with, the overall attack plan of the naval attack force and landing force.

As the operation began on 23 May at 0930, the five HO3S-ls took off from the USS Palau (CVE-122), anchored off Onslow Beach at Camp Lejeune, North Carolina, and proceeded in formation to the designated landing zone a few miles inland. The troops of the first flight were landed precisely at 1000. During the day's operations, a total of 66 Marines and a considerable amount of communications equipment were transported to the beach by helicopter. A total of 35 flights was made between the Palau and the landing zone.

The squadron concluded from its participation in PACKARD II that "transport helicopters capable of carrying at least eight troops were urgently needed if combat troops were to be landed expeditiously and in battle formation. Also, that "in order to use the space available in a CVE to full advantage, it would be necessary that embarked helicopters be capable of movement up or down on the ship's flight deck elevators," and in order to do this expeditiously, it was stressed " that automatic blade folding devices must be developed."

In response to the Commandant's directive of December 1946, officers of the MCS were busily engaged in developing a concept covering the tactics and techniques of the employment of helicopters in an amphibious operation and by November 1948 the school had published the world's first printed textbook on the subject entitled "Amphibious Operations-Employment of Helicopters (Tentative)". It was originally printed in mimeograph form in 1947 as an instructional guide for use within the school and later was used for th e planning of Operation PACKARD II. The booklet was numbered 31 in a series of publications on amphibious operations and was written jointly with representatives from HMX-1, but under the overall supervision of the Senior School's Director and senior member of the Helicopter and Transport Seaplane Board, Colonel Robert E. Hogaboom.

Phib-31 spelled out the many advantages of the helicopter to the new amphibious concept: " [the helicopter's] ability to circumvent powerful beach defenses, and to land assault forces accurately and at any desired altitude, on tactical localities farther inland endow helicopter operations with many of the desirable characteristics of the conventional airborne attack while avoiding the undesirable dispersal of forces which often accompany such operations. The helicopter, furthermore, when transported to the scene of operations in aircraft carriers, makes operations possible at ranges which have not yet been achieved by the existing conventional troop carrier types.

HMX-1 took part in Operation PACKARD III which was the MCS amphibious command post exercise of 1949. The operation was held again at Camp Lejeune, North Carolina, and was basically the same as PACKARD II in which the squadron had participated the previous year. For PACKARD III, the squadron's aircraft were divided into three separate sections. The main echelon consisted of eight HRP-ls based on board the USS Palau and, for problem purposes, represented a full helicopter aircraft group of 184 HRPs operating from six CVEs for the lifting of a complete regimental combat team. Each HRP helicopter carried six fully-equipped combat troops from the carrier for approximately 10 miles under a heavy cover of fighter aircraft which were simulating smoke and strafing runs on the defending forces. A total of 230 passengers were carried in addition to 14,000 pounds of cargo. High winds and rough seas encountered during the entire operation swamped many landing boats as they approached the beach and upon their return they experienced great difficulty in tying up to their respective attack cargo ships (AKAs).

The high point of May 1950 for HMX-1 was Operation PACKARD IV, which took place during the final week of the month. Six HRP-ls and two HO3S-1 helicopters landed on board the USS Mindoro (CVE-120) at Norfolk, Virginia, after which the ship sailed south to a point 15 miles off the coast of Camp Lejeune. The operation lasted only two days during which five HRPs and two HO3Ss carried ashore a total of 120 troops and over 20,000 pounds of cargo.

The Marine Corps was also investigating the feasibility of transporting troops from friendly bases to hostile beaches by assault seaplane transports, in addition to the ship-to-shore movement of troops by helicopter, and that the assault seaplane concept had resulted in an engineering study contract being awarded for a "flying LST" to the Consolidated Vultee Corporation, San Diego, California.

If the Marine Corps was to employ effectively its anticipated six squadrons of helicopters, plans for their employment had to be made. The first step was contained in Marine Corps Equipment Policy, 1950, which proposed a concept of future amphibious operations based primarily on the employment of the assault helicopter. Emphasis was on tactical surprise, featuring a vertical envelopment by helicopter in ultimate conjunction with dispersed assaults capable of rapidly penetrating selected points in the beach defenses. Commencement of the assault proper began with the launching of assault troops in helicopters and amphibian vehicles from ships underway in cruising or other dispersed formations. Landing of helicopter forces were in landing zones, from which one or more objectives might be seized. Landing of further troop components were by amphibian vehicles (taking advantage of success achieved by the helicopter borne troops) for beach approac h and assault at dispersed points. Early logistic support followed the pattern of the assault itself, using helicopters to deliver supplies to deep positions, and amphibian vehicles and trailers to transport heavy material across the beach to using units or dispersed interior units.

The Equipment Policy recommended that development of an aircraft carrier-type ship be initiated to transport the troop elements and helicopters of the landing force. It was further proposed that the construction of helicopter platforms on other type ships involved in the amphibious operation also be studied. The Navy had no firm plans at that time for providing properly configured ships for the employment of assault transport helicopters in accordance with this concept.

The Landing Force Tactics and Techniques Board, Marine Corps Landing Force Development Center, Marine Corps Schools was tasked to conduct a study on the most desirable means of embarking and transporting the troop elements and helicopters that are to execute the ship-to-shore movement in helicopters, and the Marine Corps operational requirement for appropriate shipping to permit the employment of assault transport helicopters. The first interim report was submitted as early as 16 December 1950 with the final report dated 5 January 1951. The study was entitled "Employment of Assault Transport Helicopters."

In determining the composition of the helicopter-landed force, the study group proposed employing one Marine division consisting of two regimental landing teams, an artillery group, and a division command group, totalling 10,000 officers and men. It was determined that this force would require 3,000 to 4,000 short tons of supplies and equipment. The most desirable means of embarking and transporting the troop elements and helicopters was that the helicopter-borne troops, equipment, supplies, and the helicopters should be transported together in aircraft carrier-type shipping.

The number of helicopters required to lift the main force was no less than 520 HRS-type helicopters each carrying 8- to 10-men or 208 HR2Ss carrying 20 to 25 troops each. The shipping requirements to accommodate the 8- to 10-man helicopter was established at 20 CVEs. In addition, all CVEs had to be converted to have the capability to operate at least 10 HRSs on the flight deck and store 10 on the hangar deck, plus spares. Facilities were also needed on each CVE for 500 to 600 combat troops plus approximately 200 personnel of the helicopter squadron. With the larger 20- to 25-man type helicopter, eight newly designed ships or converted CVs (fleet aircraft carriers) would be required; each one having the capacity to operate 10 helicopters from its flight deck and store 10, plus spares, in its hangar deck. The length of the CV class carriers varied from 739 feet for the Yorktown class CV to 901 feet for th e larger Lexington class. Both CV class ships had a top speed in excess of 30 knots. In this case, 1,200 to 1,500 billeting spaces would be needed for the assault troops plus the helicopter personnel. Cargo requirements were also listed as 150 to 200 short tons for the CVEs and 450 to 550 tons for each of the new or converted CVs.

There was no doubt that the larger helicopter was far superior in every way, more so in proportion than its difference in size would tend to indicate. The number of helicopters, helicopter personnel, ships, landing areas, and the complexity of the guidance system all pointed to the strong desirability of concentrating on the larger helicopter. A time limit was suggested for making a determination upon which type of ship program to pursue. If design and procurement of the 20- to 25-man helicopter (HR2S) was found to be less than two years, then the larger program should be undertaken. If, on the other hand, an adequate number of HR2Ss could not be procured, then the CVE conversion and the 8- to 10-man helicopter courses would be followed.

The USMC Tactics and Techniques Board completed a report on Marine Corps operational requirements for Naval amphibious shipping on 28 February 1951. The erection of helicopter platforms on various types of amphibious ships revealed that on conventional transports, APA (attack transport) and AKA (attack cargo) ships, space for only one helicopter could be provided without seriously limiting the ship's normal amphibious capability. This type of ship was dismissed from further study as it would require an excessive number of vessels to operate a significant number of helicopters. The LSD (landing ship dock) was found to have the capability to transport up to 60 helicopters but it too could only launch one aircraft at a time without extensive modification resulting in the loss of its original function. The LST (Landing Ship Tank) had the capability to operate five helicopters from a modified deck or transport up to 30 and then only operate two simultaneously. However, since the LST was slow, extremely vulnerable, and was considered to be of reduced application in future operations, it also was not considered further by the board. Seaplane tenders, the board pointed out, could operate only one helicopter at a time while an oiler could handle three to five, but again it was doubtful that these ship types could be diverted from their primary mission. Therefore it was concluded that a modified CVE carrier or a helicopter transport vessel specifically designed for helicopter and troop transport was the best solution. The CVE requirement to support the approved program was determined to be a total of four ships in service by 1 September 1952, with the first ship needed by 1 November 1951.

In February 1951, General Cates recommended that one helicopter aircraft carrier of new construction, or one converted from a CV or CVL, be included in the Navy's ship-building program for the next fiscal year, i.e., 1952. The Commandant pointed out that development of amphibious ships of all types had lagged in recent years and the time had arrived when constructive progress in this area was becoming necessary.

In April 1951, the Director of Marine Aviation, General Jerome, told the Deputy Chief of Naval Operations for Air (Op-5B), that the Marine Corps needed a prototype amphibious troop/helicopter transport ship and that it was essential that such a ship be developed from the keel up. That part of the Marine Corps concept which required troops, equipment, helicopters, and reasonable maintenance and operational facilities be combined in one type of ship was also pointed out. Four days later, the Commandant submitted to the CNO a request for the use of a CV or a CVE in evaluating the employment of assault transport helicopters. Unfortunately, all requests appeared to have been made in vain as the Ships Requirements Board failed to provide funds for the construction of a new ship or the conversion of a CVE in the shipbuilding programs for Fiscal Years '52 and '53.

On 17 July 1951, the Commandant proposed to the CNO a Marine Corps concept for future amphibious operations. Certain conceptual aspects had appeared in both Equipment Policy 1950 and in the studies submitted by the 1951 Tactics and Techniques Board. The Commandant declared that the time had come to settle on a fairly definite concept for employing helicopters in amphibious operations. He recommended the initiation of a program to develop the detailed techniques for large-scale ship-to-shore movement, one which would provide the fleets with some measure of ability to exploit the growing helicopter capability. In this respect, General Cates remarked to the CNO that it would be "prudent, practical, and timely to provide within the fleets the capability to land by helicopter the assault elements of one Marine division in continuous echelons." In accepting the optimistic troop-carrying capacity of the HR2S-1, as predicted by Sikorsky, General Cates also mentioned that the helicopter industry would soon produce a 36-man helicopter and that 144 of these aircraft could land the desired number of troops in execution of the concept. "Studies and past experience, " he continued, "indicate that the most desirable type of assault shipping for such a force will be ships which can accommodate the necessary embarked troops, the helicopters to land them, and the crews to operate and maintain the helicopters."

General Cates concluded: " It is becoming increasingly urgent to commence a ship conversion or building program that will parallel the availability of . . . the 36-man helicopter." The Commandant's letter also defined the specifications for transport shipping, an essential element of his future doctrine. From the landing force viewpoint, the most effective tactical landing would consist of a helicopter-borne attack mounted from a transport ship capable of embarking approximately 1,500 assault troops and operating at least 18 of the 36-man transport helicopters from the same ship. A ship with a minimum flight deck capacity of 10 such helicopters was considered to be acceptable.

Marine Corps Schools had prepared a landing force bulletin outlining the concept. The school had been tasked with the project in mid-1954 and had submitted a proposed bulletin to HQMC during December. After undergoing extensive revision, the Marine Corps officially published its concept of future amphibious operations on 13 December 1955 in Landing Force Bulletin Number 17, only nine days after formal recognition of the concept by the CNO. Landing Force Bulletin Number 17 (LFB-17) elaborated on the CNO 's position. The last paragraph summarized in the following manner:

"This concept has as its ultimate goal an all-helicopter assault which will endow the amphibious attack with maximum impact and maximum freedom of action. We have already progressed to a point at which our doctrine embraces a powerful two-pronged attack, one prong a vertical envelopment by helicopter, the other a surface assault across the beach by conventional means, with the latter constituting the main effort. In the future, while improving our still-essential beach-assault ability, we must adapt our organization and equipment, and our tactics, techniques, and training, so as to place major stress on the helicopter assault. Later, as new amphibious ships join the fleet, and as helicopters with greater load capacity become available in quantity, the beach assault can be reduced still further. Eventually, when the concept is fully realized, the beach assault can be eliminated altogether, leaving only follow-up troops and supplies, exploitation forces, and base-development units and material to be landed over beaches or through ports in the beachhead area." This appears to he the first case where the term "Vertical Envelopment" appears in an official Marine Corps document.

The latest improvements in amphibious tactics and techniques had been promulgated in two other Marine Corps documents during the period, both of which complemented the concept outlined in LFB-17: Landing Force Bulletin Number 2 ( "Interim Doctrine for the Conduct of Tactical Atomic Warfare" ) and Landing Force Manual 24 ( "Helicopter Operations") . These two documents gave wide circulation to the most important specific elements of the new concept and made possible the inclusion of new material in local training programs.



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