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Aircraft Carriers Between the Wars

At the close of World War I, Japan, having sided with Great Britain and France, gained control over the former German possessions in the Central Pacific that included the Marianas, Marshall, and Caroline Islands. These strategically placed island chains stood directly across the U.S. route to the Philippines thus establishing the potential for conflict. Under the RAINBOW strategic war plan, each hypothetical enemy was assigned a color; for example: Great Britain - red, Germany - black, Mexico - green, Japan orange. The possibility of a Japanese attack on Americas holdings in the Central Pacific was addressed in the RAINBOW strategic war plan, under the code-name ORANGE.

The ORANGE plan was one of a number of contingency war plans developed by a joint U.S. Army and Navy Board in the early twentieth century. After World War I, it was updated to reflect the current world situation. The ORANGE plan of the 1920s and 1930s assumed that the Philippines, strategically placed between Japan and the resources of the Netherlands East Indies16, would be attacked. It called for the U.S. garrisons in the Philippines as well as Guam, Midway, and Wake, to hold the islands until the Navy's forces arrived to engage and eliminate the Japanese fleet. In crossing the Pacific, the U.S Navy would be required to establish a series of island bases to facilitate en route refueling and repair. They would also need to secure bases that placed them within reach of Japans major naval installations.

Under the ORANGE plan, the aircraft carrier increased the battle fleets reconnaissance range and supported its mission to attack and secure strategic island targets within Japans sphere of influence. As such, the U.S. began developing carriers to support fleet operations in the open waters of the Pacific. In response, Japan began developing her own force to both combat a U.S. carrier fleet and to aid in carrying out an expansionist policy throughout the South and Central Pacific and Southeast Asia.

The aircraft carrier became a component of the U.S. Navy fleet with the conversion of the collier Jupiter (AC-3) to the experimental carrier Langley (CV-1) in 1922. Subsequent carrier development would be highly influenced, until the outbreak of World War II, by the arms limitation treaties stemming from World War I. The 1921 Washington Naval Conference had been the first in a series of attempts by the United States, Great Britain, Japan, France, and Italy to maintain peace by limiting the total warship tonnage for each nation. The resulting 1922 treaty established a scrapping program and restricted new capital ship construction in an attempt to limit the warship tonnage of the United States and Great Britain to 500,000 tons each, Japan to 300,000 tons, and France and Italy to 175,000 tons each. The treaty also included clauses that prevented the arming or fortifying of bases in Pacific island possessions (except for the Japanese home islands and the American Hawaiian islands). The conference also endorsed (accepted by the United States, Great Britain, Japan, France, Italy, Netherlands, Belgium, Portugal, and China) an open door policy with China that acknowledged her territorial integrity. However, subsequent naval disarmament conferences throughout the 1930s were limited in their effectiveness and ultimately the treaty process as a means to curb the naval arms race came to an end.

A warship can be thought of as a series of components that add up to the vessels total tonnage or displacement. Thus, the tonnage limits imposed by the Washington Naval Treaty had a direct effect upon carrier size and development. The basic factors that dictate warship design include (1) dimension, (2) armament, (3) armor, (4) speed, and (5) endurance or cruising range. An increase in any one of these five factors will increase the overall tonnage, as well as cost, unless there is a reduction in one of the other factors. Every warship is designed according to a series of strategic requirements that reflect the vessels function within naval operations. They must also be constructed within budgetary limits. The dimensions of the ship affect not only its costs but also its accessibility to existing harbors, docks, and canals and thus its geographic mobility. A warship must also carry appropriate armament to allow it to defeat an enemy or survive an enemy assault. However, guns, armor, and aircraft add weight and dimension as well as cost. Heavy protection can therefore affect operational speed, cruising range, and fuel consumption that are dictated by the efficiency of the power plant. Powerful propulsion machinery can increase weight, take up valuable internal munitions and fuel storage space and of course, add to the cost. Warship design, therefore, requires setting priorities and working through a series of compromises in order to meet strategic and budgetary requirements. In addition to the pre-World War II treaty considerations and economic factors that affected capital ship construction, fleet exercises, and ultimately wartime operational experience had a significant impact on carrier development.

For the United States, the Washington Naval Treaty resulted in the cancellation of six battle cruisers scheduled for construction. The treaty also set the limits on new carrier construction at 27,000 tons each. Carrier conversions were set at 33,000 tons with an additional 3,000 tons allowed for protection against air and underwater attack as authorized under the treatys capital ships modernization clause. Total carrier tonnage for the United States was set at 135,000 tons. In an attempt to salvage the work that had already begun on the Lexington-class battle cruisers, Congress authorized the conversion of two partially constructed hulls. Completed in 1928, these vessels became the second and third carriers of the U.S. Navy fleet, Lexington (CV-2) and Saratoga (CV-3). The two 36,000-ton Lexington-class carriers were 888 feet overall and supported a compliment of sixty-three aircraft. They were designed to operate at high speeds within a fleet of fast-moving surface combatants.

With the conversion of Lexington (CV-2) and Saratoga (CV-3) approximately 69,000 tons remained for additional carriers. Based on the Lexington class, the next desired carrier would provide high speed, high airplane carrying capacity, and suitable armor and armament. Of the five 13,800-ton carriers proposed by the Navy for a five-year building plan (1929-1933), Congress approved one construction. Ranger (CV-4) entered service in 1934 and was the first U.S. carrier built from the keel up. At 769 feet overall, she was significantly smaller than the Lexington class. However, Ranger had much larger hanger area for greater aircraft stowage and could support some seventy-six aircraft. This was achieved by reducing armor and armament and sacrificing speed. With her lower propulsion power, Ranger was designed to operate within slower moving battle fleets.

As with the previous carriers, the Yorktown class was limited by treaty-imposed tonnage restrictions. However, they differed from their predecessors in that their design was based on the experience gained by the large carriers Lexington and Saratoga, and the small carrier Langley in fleet exercises rather than war games data. Under the remaining tonnage available, a maximum of two 27,000-ton carriers could be constructed. Studies for 15,000-, 20,000-, and 27,000-ton ships that emphasized aircraft capacity, and the protection, armament, and speed that had been lacking in Ranger were developed. The final design produced two 20,000-ton ships of 809 feet overall. The Yorktown (CV-5) and the Enterprise (CV-6) were both launched in 1936. Remaining tonnage was allocated to the construction of another small carrier, Wasp (CV-7), launched in 1939. Hornet (CV-8), a slightly improved version of the Yorktowns, was launched in 1940 when treaty limitations were no longer in force. The Yorktowns, more heavily armored and with increased speed as well as a capacity for eighty to ninety aircraft, were essentially an improved version of Ranger. As well, it was from their design that the next and largest group of U.S. Navy aircraft carriers was derived, the Essex class.

Between 1939 when studies for the Essex-class carriers began and April 1941 when the first vessel, Essex (CV-9) was laid down, war had erupted in Europe, the Pacific was in turmoil, and United States entry into a conflict against Japan and the European Axis powers was just months away. Within this span of time Germany had occupied most of Europe and gained Italy and Japan as allies under the Tripartite Pact where the three countries pledged mutual military support and recognized each others regional supremacy. Great Britain was left to face the Axis powers alone, and her colonies throughout the Middle East, Asia, and the Pacific as well as those of the Netherlands and France were left with minimal defenses. Tensions were mounting in the Pacific, as well, as Japan continued to expand her influence throughout the area. Between 1931 and 1939, Japanese forces had occupied Korea, Manchuria and Hainan Island, and carried out air raids and other acts of aggression against cities on the Chinese mainland. As well, they occupied the Spratly Islands held by French Indochina.

By August 1940, with permission of Vichy France, Japan began to assert more control over Indochina and showed a keen interest in the resources of the Netherlands East Indies, Malaysia, Borneo, Singapore, and Burma. In November 1940, Japan began fortifying the Marshall and Caroline Islands with airfields and seaplane bases. With a preference not to be drawn into conflict, the United States initially sought to protest Japans military expansion through economic sanctions. In July 1940 Congress began restricting the export of resources associated with industrial production and wartime operations in Japan. All movement of such goods was halted in July 1941 through an executive order freezing Japanese assets in the United States. Concurrently, the United States sought to support Great Britains European war by supplying those resources and products that would facilitate an Axis defeat.

With a strong possibility of a two-ocean conflict on the immediate horizon, development of the Essex-class carriers reflects the United States urgent need to prepare for such a confrontation. Although no longer limited by treaty tonnage restrictions as with previous classes, there was a pressing need for carriers and thus little time to develop a design radically different from a proven predecessor, the Yorktown class.25 Keeping in mind that ship-based air power would play an important role in naval warfare, the Navys major concern affecting the Essex design was the ships capacity to carry and operate aircraft. Under the desired characteristics developed, the new class would be capable of carrying four squadrons, a fifth reserve squadron, and sufficient aircraft replacement parts. As well, the Essexes would be fitted with armor and armament capable of withstanding bomb and torpedo attack. It was also important that they be able to accommodate wartime advancements in aircraft technology, anti-aircraft weapons, and radar.

Based on the Yorktown class, six designs were developed between July 1939 and January 1940. The design that was chosen would result in a ship that had a straight flight deck, as with all her predecessors, and was heavier than the Yorktown at 27,000 tons. With an overall length of 872 feet it would support a complement of ninety-one aircraft. Although sacrificing the extra weight of flight deck armor for increased speed, like the Yorktowns, Essex had an armored hanger deck and 4-inch belt armor. Armament specifications included twelve 5-inch 38 caliber dual purpose guns, thirty-two 40-mm and forty-six 20-mm anti-aircraft guns along with two Mark 37 and eight Mark 51 directors for fire control. The Essexes were initially designed without radar specifications; these would be subsequently added through wartime modifications and upgrades. In early 1940 four Essex-class vessels were ordered (CVs 9-12). By May 1940 seven more were authorized (CVs 13-19) in conjunction with a 70% expansion of the Navy. In December 1941, CV-20 and CV-21 were authorized followed by CVs 31-40 in August 1942 and CVs 45-47 in June 1943. CV-35 and CV-46 were cancelled after the war.

In addition to the Essex class, which served as the Navys primary fleet carrier, the United States built two other classes of carriers. These consisted of an emergency light carrier designated CVL, and an escort carrier, the CVE. As well, the design of a large, armored-deck carrier, designation CVB, was developed. In 1941, the United States had seven carriers but by early 1942 all but one had become casualties of the war. The Independence-class light carriers (CVLs 22-30) were therefore developed to meet the Navys pressing demand for carriers while the Essex class was under construction. Ordered in June 1942, all nine carriers, converted from Cleveland-class light cruiser hulls, were completed by the end of 1943. At 10,000 tons with a compliment of thirty aircraft, the light carriers served with the fast fleet groups in air combat and aircraft transport missions.

The escort carrier program included four major classes of vessels: Sangamon, commissioned in 1942, Casablanca, commissioned 1943-1944, Bogue, commissioned 1942-1943, and Commencement Bay, commissioned 1944-1945. Close to ninety escort carriers were constructed for the use of both the U.S. and Royal Navies in convoy and trade route protection as well as movement of expeditionary forces and support of landing operations in the Pacific. Plans for the Midway class of large carriers began in 1941 after Great Britains wartime carrier experience had illustrated the effectiveness of deck armor against aerial bombardment. The first contract went out in 1942. However, the three ships of this class completed, Midway (CVB-41), Franklin D. Roosevelt (CVB-42), Coral Sea (CVB-43), were not available until 1946-1947, and did not participate in World War II.



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