World War II Database

Contributor: Bob Bryant

Aircraft carriers played a large part in deciding the outcome of World War II's decisive victories at sea that, in turn, created the essential conditions for the war's decisive victories on land. Shortly after the war began, carriers bypassed battleships and and became the capital ships around which combatant navies centered their fleets for major offensive operations. Carrier aircraft could deliver bombs and torpedoes to targets hundreds of miles away, while even battleships with the largest guns could only rain destruction down on targets within 26 miles. Accordingly, the major naval powers, the United States, United Kingdom, and Japan, commissioned a total of only 23 new battleships during the war but commissioned a total of 55 new fleet carriers (CV) and light carriers (CVL). A total of 145 escort carriers (CVE) and merchant aircraft carriers (MAC) were also launched.

During the entire war, battleship guns sank only a single fleet carrier and a single battleship. In comparison, carrier-launched aircraft damaged, sank, or took part in sinking 19 battleships, including eight at Pearl Harbor. Along with Pearl Harbor, the earlier use of carrier-launched aircraft at Taranto demonstrated their effectiveness. After the Battle of Midway, Japan began leaving battleships out of major naval engagements, and battleships of all navies were more often used for bombarding land targets than engaging in naval battles.

Successful naval battles kept shipping lanes open for a combatant's movement of troops, guns, ammunition, tanks, warships, aircraft, raw materials, and food. Without the Allied victory in the Battle of the Atlantic, Britain could not have fed her people or withstood Axis offensives in Europe and North Africa. Without Britain's survival and without Allied shipments of food and industrial equipment to the Soviet Union, that country's military and economic power would likely not have rebounded in time for Russian soldiers to prevail at Stalingrad and Kursk. Without victories at sea in the Pacific Theater, the Allies could not have mounted amphibious assaults on or maintained land forces on Guadalcanal, New Guinea, Saipan, The Philippines, Iwo Jima, or Okinawa.

Number of Aircraft Carriers In Operation During the War

The United States, United Kingdom, and Japan were the only combatants that made significant use of aircraft carriers during the war. The table below shows the number of ships each country operated between July 1937 and August 1945 that had flight decks for both launching and recovering aircraft at sea. Early in the war, the Royal Navy introduced fighter catapult ships (FACs) and catapult aircraft merchant ships (CAMs) for convoy escort that could launch aircraft by catapult, but there was no provision for recovering them.  After completing an attack, the planes were simply ditched and their pilots recovered.  Late in the war the Japanese Army introduced some ships that had flight decks from which aircraft could be launched, but the decks were too short for the aircraft to land on. These UK and Japanese ships are not included in the table.

France had one aircraft carrier, but it did not see action during the war. Canada operated two of the escort carriers included below under Britain's carriers using British aircrews. All but six of Britain's escort carriers were produced in the US.

Aircraft Carrier Functions

Aircraft carriers were used in a wide variety of operations. They fought in major naval battles against enemy fleets. They supported invasions during which carrier-launched aircraft bombed enemy positions, spotted for warship bombardment guns, and delivered aircraft to land bases afterward. They raided enemy positions, keeping them off-balance and reducing their combat capability. Carrier aircraft denied shipping lanes to enemies, sank raiders and submarines, escorted conveys, and delivered aircraft to other carriers and to land bases. Carriers were also used for training pilots and, at the end of the war, helped repatriate troops to their homes.

The combatants differed in the functions they emphasized for carrier use, in part as a result of the challenges presented by their principal theater of operations. The table below indicates the percentage of carriers each combatant used for each function. For example, the US Navy operated a total of 33 fleet and light carriers during the war. Seventy-three percent of these carriers participated in naval battles at one time or another. Eighty-five percent were involved in support of invasions, etc. Escort carriers, although initially envisioned by many to perform only in support roles, ultimately performed all of the functions that the fleet and light carriers did.

Overview of Operations Involving Aircraft Carriers

Britain entered the war in 1939 with a total of seven fleet and light aircraft carriers, all but one of which was in the Atlantic Theater. Three of these carriers were sunk before the US entered the war. During the war in the Atlantic Theater, Allied carriers transported and protected transportation of troops, aircraft, tanks, oil, and food from or routed through North America or up the West African coast to Britain, Russia, North Africa, and continental Europe. Allied escort carriers screened by corvettes, destroyers, and destroyer escorts proved more successful and cost-effective than using fleet carriers, battleships, or cruisers for protecting convoys from attacks by Axis submarines, raiders, and land-based aircraft. By mid-1943, the Axis threat of cutting essential Allied supply lines had passed. By this time, however, German battleships and submarines had sunk a total of five British fleet and light carriers, as shown in the table, below. Three Allied escort carriers had also been sunk.

At the time Japan attacked Pearl Harbor, she had nine carriers in the Pacific and had superiority both in number and effectiveness. During the 1930s, Japan had originated and refined the massed use of carriers and carrier aircraft in combat operations. For the first six months of the war, her unequaled Mobile Force of six fleet carriers (Kido Butai) was able to roam virtually at will from Hawaii in the east to Ceylon in the West. Japan's carriers supported successful invasions of the American Philippines, British Malaya and Burma, and the Dutch East Indies.

Between May and October 1942, however, Japan lost six of her carriers as Japanese and United States navies fought four major naval battles between fleets centered on their aircraft carriers. During these battles, opposing warships never came within sight of each other nor fired their guns at other warships. Aircraft alone did the attacking. The first of these battles thwarted the Japanese attempt in the Coral Sea to isolate Australia. The second halted the expansion of Japanese control eastward in the Pacific toward Midway Island. The next two helped sustain the American presence on Guadalcanal. These four engagements were costly for both sides. At the time Pearl Harbor was attacked, Japan had a total of nine fleet and light carriers in the Pacific theater. The United States had four in the Pacific with another two far away in the Atlantic. At the end of October 1942, after battle attrition from sinkings and damages, Japan had only three such carriers fully operational in the Pacific theater and The United States, for a two-week period, had none. Though costly, the battles were strategically advantageous for the Americans, contributing significantly to the shift of strategic initiative in the Pacific Theater from Japan to the United States. Japan did not engage her carriers in a major initiative again until the Battle of the Philippine Sea in mid-1944.

Number of Operational Aircraft Carriers

Carriers were not available for operations all of the time they were afloat. After commissioning, there were delivery periods, refits and sea trials before carriers became operational. After first becoming operational, combat damage, operational mishaps, or damage from typhoons could render a carrier not combat-ready. Taking into account all the factors that kept aircraft carriers out of combat after first becoming operational, fleet and light carriers were typically operational about 80% of the time. They were typically out of service 5% to 15% for combat-related damage repair and 5% to 10% for delivery and refitting to otherwise improve performance.

The number of operational carriers available to the combatants at any point in time affected the capability, plans, and outcomes of military operations in both the Atlantic and Pacific theaters throughout the war. Taking into consideration the time for construction, shakedown trials, delivery, refitting, combat damage, and sinkings, the table below shows the number of fleet and light carriers that were operational for each combatant in each combat theater at the end of each month. The Pacific Theater includes the Indian Ocean and the Atlantic Theater includes the Mediterranean Sea.

The table capsulizes the course of the war for aircraft carrier operations. It reflects how Japan more than doubled the number of her carriers between leaving the Washington/London naval treaties in 1936 and the time she attacked Pearl Harbor in December 1941. It also reflects the attrition for carriers during the formative year of 1942. It reflects the industrial capacity of the United States, illustrating how she could make good her losses of 1942 while Japan could not. Finally, it reflects the shift of British carriers to the Pacific after the Allies prevailed in battles for Atlantic waters. Note also that, after mid-1942, the percentage of aircraft carriers afloat that were in fact available for combat operations was typically less than 70%. During the Guadalcanal campaign that year, that percentage fell below 50%. From then until mid-1944, Japan did not engage her carriers in a major operation. When at last she did, the rest of her carriers were sunk or damaged.

Notes:

The details behind the numbers in the above tables may be found in the "Documents" section at the "Reference" tab at the World War II Database:

• Collection of Statistics on Japanese Aircraft Carriers
• Collection of Statistics on UK Aircraft Carriers
• Collection of Statistics on US Aircraft Carriers

Visitor Submitted Comments

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2.  Bob Bryant says:
24 Oct 2020 07:24:22 AM

Thank you very much for your questions. The counts include only carriers that were operationally ready between Jul 1937 and Aug 1945 that had flight decks for both launching and recovering aircraft at sea. The 78 CVEs include 1 Langley, 1 Long Island, 1 Charger, 10 Bogue/Attacker, 1 Bogue/Ruler, 4 Sangamon, 50 Casablanca, and 10 Commencement Bay class. Details are included in the recently published table at WW2db/Reference/Documents/US Aircraft Carrier Functions.

Your question about the Marus is well taken. The Japanese and British both used ships that could launch aircraft but not recover them, so they are left off the list. The Shimari Maru and Yamashio Maru were both commissioned before war’s end but neither became operationally ready to function as carriers so they are not included either.