Beginning with Pearl Harbor, the Pacific theater in World War II centered largely about the operations and clashes of the Japanese and American aircraft carrier forces. Not only did the overwhelming victory achieved by the Japanese carriers on 7 December 1941 demonstrate that battleships were highly vulnerable to air attack, but it forced the U.S. Navy to develop the resources, strategies, and tactics to permit reliance upon the aircraft carrier as the capital ship of the future.

Tactics and material evolved during the war as experience was gained at the major carrier vs. carrier battles of Coral Sea (7-8 May 1942), Midway (4 June 1942), Eastern Solomons (23 August 1942), Santa Cruz (26 October 1942), Philippine Sea (19-21 June 1944), and Leyte Gulf (24-25 October 1944). This article will examine the nature of carrier warfare between 1941 and 1945 by comparing the hardware (ships, airplanes, and weapons) and software (tactics and strategy) of the Japanese and American fleets.

The Carriers

Japan took an early lead in aircraft carrier development by launching the 7470-ton Hosho in 1922. Within 19 years she had been joined by six large fleet carriers (CVs) and an additional light fleet carrier (CVL). Japan's wartime construction totalled 18 additional flattops, ranging from the 11,190-ton Chiyoda and Chitose (formerly seaplane carriers) to the gigantic 64,800-ton Shinano, which was constructed on a Yamato-class battleship hull but did not even survive her maiden voyage. Many of these vessels were converted from existing merchant ships or passenger liners; several were too slow to serve with the fast fleet carriers and were relegated to the tasks of escort carrier (CV E) duties.

In addition, Japan converted two capital ships, Ise and Hyuga, to weird battleship-carriers, with a partial flight deck in place of the two aftermost 14-inch gun turrets.

The mainstays of Japan's carrier force were Kaga, Akagi, Hiryu, and Soryu (all sunk at Midway), plus sisters Shokaku (lost at the Battle of the Philippine Sea) and Zuikaku (survived until Leyte Gulf). These six ships began the war by launching two waves totalling 384 aircraft at Pearl Harbor. They were all fast (28-34 knots), well-armed ships, with the Kaga the largest at 38,200 tons. The smaller half-sisters Hiryu and Soryu typically operated 73 airplanes, while Kaga and Akagi could handle up to 90 fighters, torpedo planes, and dive bombers.

The United States began the war nearly equal to their enemy in carrier strength. At the beginning of hostilities the fleet included the veteran 33,000-ton Lexington and Saratoga, both commissioned in 1927 after being laid down as battlecruisers; the CVL Ranger; the Langley, relegated to seaplane tending after initiating America's carrier force in 1922; and the three members of the newer 20,000-ton Yorktown class, including Enterprise and Hornet. These ships were joined shortly by the smaller (14,700 tons) Wasp. But an efficient building program rapidly brought the excellent Essex-class ships into service in 1942, with 14 of the 31,000-ton vessels being completed by the end of the war. All of these CVs had speeds in excess of 30 knots and could operate between 84 (Wasp) and 100 (Essex) aircraft.

Besides this formidable array of fast carriers, 9 ships of the Independence class of CVLs were built using light cruiser hulls. With a displacement of 11,000 tons and a speed of 32 knots, these ships operated alongside the bigger carriers and contributed about 45 airplanes apiece. For antiaircraft protection the Independence and its sisters relied upon four 5-inch gun mounts, as well as 26 40mm and 40 20mm light AA guns.

Air cover for convoys and ground operations could be provided by the seventy escort carriers built during the war. These small (7,800-12,000 tons) ships were rapidly converted from merchant ship or oiler hulls. The 45 ships of the Casablanca class were constructed in the incredible time of 76 days each! With speeds of 18 or 19 knots, the CVEs typically operated 21-30 fighters and torpedo bombers. The slow speed and short flight decks of the "baby flattops" made it difficult to launch heavily laden dive bombers without a catapult, as was used on the larger carriers. A CVE sported only one or two 5-inch guns as heavy AA armament, as well as numerous smaller guns.

Conceptions of aircraft carrier gunpower changed substantially as building programs progressed. Kaga, Akagi, Lexington, and Saratoga were all originally designed to be capital ships, and as carriers initially carried main armaments of eight or ten 8-inch guns.

Saratoga was even outfitted with four 21-inch torpedo tubes! Four of Akagi's 8-inchers were replaced with twelve 5.5 inch antiaircraft guns in a 1938 refit, and just before the war began the two Lexington- class ships had their 8-inch turrets removed and replaced with additional 5-inch AA weapons, too. The Essex-class vessels boasted twelve dualpurpose 5-inch 38- caliber guns.

As wartime experience was gained the light AA weapon density was also increased. The original sixteen 1.1-inch rapid-firing guns mounted on the Yorktown and its sisters eventually evolved to some seventy 40mm guns in twin and quadruple mounts and a like number of 20mm weapons on the later ships. Similarly, the Japanese carriers employed as many as sixteen 5-inch AA guns (Hiyo and Junyo) in addition to numerous 25mm, 37mm, and 47mm light antiaircraft cannon. Armored Flight Decks

Perhaps the greatest shortcoming of the American carriers was their lack of an armored flight deck, a feature shared by their Japanese counterparts until Taiho was completed in 1944. While this sacrifice increased the aircraft capacity of the ship, it also increased the vulnerability of the carriers to kamikaze and conventional bombing attacks.

The British fleet carriers such as the lllustrious class had up to 3 inches of armor on the flight deck and 2.5 inches on the hanger deck, which resulted in much less interference with flight operations by bombs and deck crashes (friendly or enemy). The U.S. carriers had a flight deck constructed of 3-inch teakwood easily penetrated by bombs and put out of action. The Essex and Yorktown did sport about four inches of armor over the machinery spaces at the waterline, while the Lexington and Saratoga were somewhat better protected.

Despite the lack of extensive armor, an aircraft carrier could absorb a surprising amount of battle damage without going under. The actual outcome of cross- referencing bomb and torpedo hits with a carrier's structural durability record depended on such variables as the status of aircraft on board (stowed or fueled and armed) and the efficiency and nature of damage-control procedures used.

For example, at Coral Sea the Lexington took between 3 and 5 torpedo hits on her port side in addition to three direct bomb hits from the Japanese strike force. An hour later all fires were out and the ship was making 25 knots on an even keel. Then came an enormous explosion which soon set the entire vessel on fire and forced her abandonment. This mysterious blast was attributed to the accidental ignition of gasoline vapor leaking from damaged tanks. It still required four more torpedoes from an American destroyer to finally send the Lady Lex beneath the waves.

Similarly, the Hornet was stung by 3 bombs, 2 torpedoes, and 2 enemy airplanes in a single strike at the Battle of Santa Cruz. The fires were brought under control in time for a second enemy strike to contribute one additional torpedo and another bomb. After being abandoned, the carrier survived two more bomb hits, over 500 rounds from American 5-inch guns, and no less than twelve U.S. torpedoes. Four hours later the still drifting hulk was finally sunk by four Japanese Long Lance torpedoes. Now, that's tough!

The great American naval victory at Midway, in which Kaga, Akagi, Hiryu, and Soryu were devastated by five, two, four, and three bomb hits, respectively, was aided by the fact that the Dauntless dive bombers caught the enemy with a full load of armed and fueled planes on the flight and hanger decks.

The exploding bombs touched off Japanese bombs, torpedoes, and aviation fuel to result in conflagrations that quickly engulfed the entire ship. While all but Kaga had to be sunk by torpedoes, the amplified bomb damage effectively rendered the four carriers unsalvagable.

The Aircraft

Although the U.S. Navy was initially on a par with the Japanese in regards to carrier strength, it was greatly inferior in the field of naval aviation.

The Japanese began the war with effective models of all three major types of carrier airplanes: fighter (the superlative A6M "Zeke", popularly known as the "Zero"); dive bomber (the D3A "Val"); and torpedo/level bomber (the slightly obsolescent B5N "Kate"). First-line carrier airplanes deployed by the U.S. at the start of the war were the F4F Wildcat fighter, the SBD ("Slow But Deadly") Dauntless dive bomber/scout, and a hopelessly outclassed torpedo bomber, the TBD Devastator. Table 1 provides comprehensive data for these and later types of carrier aircraft.

The qualitative superiority of the enemy carrier planes came as a rude shock to American aviators. The Zero was much faster and more maneuverable than the Wildcat and had a far better rate of climb. The Devastator was a sitting duck when lumbering along at 100 knots or so with a torpedo: at Midway 35 of 41 TBDs were shot down without scoring a single hit. Only the Dauntless was really an adequate weapon, and it remained in service throughout the war.

The outstanding range and maneuverability of the Japanese planes were bought in part at the cost of armor and self-sealing fuel tanks, and the American planes were consistently able to absorb much more battle damage than their opponents without being destroyed.

Later improvements in carrier warplanes tipped the scales in favor of the Americans. The F6F Hellcat clearly outperformed the Zero, which was improved throughout the war but never replaced by a better type. Carrying much more ammunition for its six .50-cal machine guns than did the Wildcat, the Hellcat had a belly tank for longer range and could act as a fighter-bomber by carrying up to a 1000- pound bomb load. Despite initial difficulties in adapting to carrier operations, the F4U Corsair eventually became one of the best fighter planes of the war. The TBF Avenger was a vast improvement over its predecessor; it could carry a 21 -inch torpedo or 2000 pounds of bombs in an enclosed weapons bay.

The Japanese did not stand still in the evolution of carrier aircraft, either. The Val dive bomber was replaced by an extremely fast plane, code-named "Judy", starting in 1942, and the venerable Kate gave way to the B6N "Jill". By war's end the American qualitative lead was augmented by the great numbers of airplanes which were produced.

An especially important factor which favored the U.S. Navy was that trained pilots could be produced in the States on a large scale, whereas most of the experienced Japanese pilots had been lost by the Battle of Midway and their replacements were of much lower quality.

Table 1. Japanese and American Carrier Aircraft
Model	Nationality	Type	Year Introduced	Top Speed	Maximum Range	Notes
F4F Wildcat	U.S.	F	1940	318	900	A
F6F Hellcat	U.S.	F/FB	1942	380	1090	-
F4U Corsair	U.S.	F/FB	1943	446	1000	-
SBD Dauntless	U.S.	DB	1941	245	456	B
SB2C Helldiver	U.S.	DB	1943	295	1165	-
TBD Devastator	U.S.	TB	1937	206	435	C
TBF Avenger	U.S.	TB	1942	278	1215	-
A6M Zeke	Japan	F/FB	1940	354	1200	D
J2M Jack	Japan	F	1943	360	-	E
D3A Val	Japan	DB	1941	281	969	-
D4Y Judy	Japan	DB	1942	360	945	-
B5N Kate	Japan	TB	1937	235	609	F
B6N Jill	Japan	TB	1943	299	1084	G

Notes. A: F = fighter; FB = fighter-bomber; DB = dive bomber; TB= torpedo bomber; speed in miles per hour; range in miles. B: with bomb; 773 miles as scout bomber. C: with torpedo; 700 miles with bombs. D: 1940 miles with drop tank. E: very few of these planes entered service. F: 1237 miles in search mode. G: 1895 miles in search mode.

Weapons

It is interesting to compare the guns, bombs, and torpedoes used by the opposing forces between 1941 and 1945. The standard American aircraft gun was the.50- cal machine gun, although .30-cal machine guns were often used as flexible defensive weapons in bombers, and some later planes were armed with 20mm cannon.

The .50-cal machine gun was accurate at ranges up to several hundred yards; the lightly built Japanese planes did not hold up well under the converging fire of six such weapons as mounted in the Wildcat, Helicat, and Corsair. Japanese aircraft mostly carried 7.7mm machine guns, augmented in some models by 20mm cannon.

Ordnance used by the Japanese in both the dive and level bombing roles included 66, 132, 551, and 1760-pound bombs. The last, a converted battleship projectile, was an armor-piercing weapon used with good results on the American battleships at Pearl Harbor.

Similarly, the Americans had bombs of 100,250, 500, and 1000 pounds. At the battles of Coral Sea and Midway the U.S. dive bomber pilots found that the instantaneous fuses on their thousand pounders were fine for flight deck destruction, but caused little internal damage. On the other hand, the delay fuses utilized in later operations would penetrate the flight deck and cause internal damage without either seriously disrupting flight operations or blowing holes beneath the waterline.

It was with torpedo technology that the Japanese really shone and the Americans suffered. The Japanese Type 91 21-inch aerial torpedo, weighing 1764 pounds, could be dropped from a height of several hundred feet from a Kate flying at top speed, and would reliably explode after racing to its target. In contrast, the American Mark 13 21-inch torpedo was a miserable weapon. Not only did it have to be dropped from an altitude of 200 feet or less by an airplane flying no more than 130 miles per hour, but it only moved at 33.5 knots--slower than some of the enemy's warships. Even if it managed to encounter a target, the torpedo's unreliable magnetic exploder too often prematured or simply failed to detonate the 600-pound warhead. The failure of the U.S. Navy to replace this almost useless torpedo resulted in many missed opportunities throughout the war. The Mark 13 was finally improved in 1944.

Reconnaissance and Early Warning

Before worrying about how best to attack an enemy fleet, you first have to find it. The Japanese Navy outperformed its American counterpart throughout the war in the field of air search. Even as late as the Battle of the Philippine Sea, the U.S. scout bombers could only.search out to a radius of 350 miles or so, whereas the long-ranged Kates and Jills gave eyes to the Japanese carrier commanders out as far as 560 miles.

Both sides relied upon the additional searching abilities of long endurance seaplanes such as the PBY Catalina and the H8K "Emily"; the latter had a reconnaissance range of nearly 4500 miles. The more generous range of the Japanese warplanes also provided an advantage in combat: a Japanese air strike could be launched up to 300 miles from its targets while 225 miles was the maximum strike range of U.S. carrier planes, even when using belly tanks.

However, except at Philippine Sea where the U.S. strike took off at a distance of 275 miles from the enemy and suffered heavy operational losses due to fuel shortages, strikes were rarely launched more than 200 miles from the opposing forces.

It is also helpful to spot the incoming enemy air strikes before they are on top of you, and in this the U.S. Navy excelled. Yorktown was equipped with XCAM air search radar as early as March 1941, two and a half years before radar was installed on Japanese carriers. The American radar picked up incoming attackers at ranges like 68 miles (Coral Sea), 46 miles (Midway), 23 miles (Santa Cruz), 88 miles (Eastern Solomons), and even 140 miles (Philippine Sea).

This early warning gave the flattops time to launch fighters to intercept, stow ordnance, and fill empty fuel lines with carbon dioxide gas, a fire prevention trick learned at Coral Sea. Unfortunately, fighter control from the defending carriers was very poor until later in the war, and many times only a few of the Wildcats or Hellcats on combat air patrol (CAP) actually contacted enemy flights. A very serious difficulty was that the altitude of the attacking planes was often greatly underestimated.

By 1944 air-surface communications and coordination were much improved, with the result that the four Japanese strikes that attacked 15 American CVs and CVLs at the Battle of the Philippine Sea encountered some 220 defending Hellcats. In an action that became known as "The Marianas Turkey Shoot", the Hellcats assisted the fleet's antiaircraft gunners in downing about 200 of the 328 attackers.

Combat Tactics

A typical U.S. carrier air strike from one of the 1942 carrier battles consisted of 8 fighters, 23 dive bombers, and 10 torpedo bombers; the corresponding Japanese strike had an average composition of 13 fighters, 19 dive bombers, and 10 torpedo bombers. By 1944 the balance had shifted such that both sides included many more fighters with each attacking wave.

On occasion fighter planes from one strike would even attack the bombers of an enemy force as the two air strikes crossed paths en route to their respective targets! As experience was gained, the mix of airplane types operated on the U.S. carriers changed substantially. Whereas in 1942 Essex put to sea with 36 fighters, 36 dive bombers, and 18 torpedo bombers, by 1945 a typical fleet carrier sported a complement of 15 each of dive and torpedo bombers and no less than 73 Hellcats.

There is an art to the proper deployment of fighters, dive bombers, and torpedo bombers involved in an air attack. The desired strategy involves simultaneous attacks by both types of bombers to split the CAP and antiaircraft defenses. In practice this was rarely achieved, since coordinating the arrival of different types of aircraft cruising at different speeds and altitudes after being launched from various aircraft carriers was nearly impossible. After approaching the enemy at low or medium altitude (7000 feet, for example), the torpedo planes would try to make an "anvil" attack, with two groups simultaneously attacking a target from both sides of the bow to try and guarantee at least one hit.

The dive bombers flew at a fairly high altitude, perhaps 13,000 to 19,000 feet, then plunged at an angle of 70 degrees or more and released their bombs about 1500 to 2500 feet from the sea. Usually few direct bomb hits were obtained on a narrow flattop twisting and turning at 30 knots or more. Even a near miss could inflict damage with bomb splinters, or by the concussive force of an underwater explosion buckling hull plates and damaging machinery.

Besides the fighters on CAP a carrier force relied upon maneuverability and massed antiaircraft fire for defense. The carrier would typically be screened by several cruisers and numerous destroyers (for antisubmarine activities), and perhaps a fast battleship or two with its enormous concentration of antiaircraft weapons. By 1944 U.S. Navy doctrine called for the division of a carrier "task force" into several "task groups", each of which included a total of three or four fleet and light fleet carriers surrounded by their escorts in a circular screen for maximum AA effect.

The task groups operated far enough apart to present distinctly separate targets to an enemy strike force. Heavy antiaircraft gunfire was improved with the introduction of a proximity fused shell for the standard 5- inch 38-caliber dual-purpose gun used on nearly all American warships, and with the employment of radar-directed fire control by 1944.

The Japanese also experimented to find the optimum deployment of the flattops in a multi-ship task force. For example, at Santa Cruz the Junyo and two destroyers were stationed about 100 miles from the other carriers involved, Shokaku, Zuikaku, and Zuiho. This was felt to be close enough that all four ships could launch strikes against a single target, but distant enough that both groups would not be attacked at the same time.

The Japanese occasionally stationed a CVL some distance from their main carrier force as "bait" for an American strike, and the U.S. Navy fell for it more than once. At the battle of the Eastern Solomons the 10,600-ton Ryujo was sunk in return for damage to the Enterprise, while the heavy carriers Zuikaku and Shokaku escaped unscathed. And at the ultimate naval battle of the war, Leyte Gulf, the entire remaining Japanese carrier fleet served as bait to draw off the U.S. Third Fleet's carriers and battleships so that Japanese heavy surface forces could destroy the transport fleet supporting an amphibious landing then taking place in the Philippines. It almost worked.

In a mediocre performance due to fierce enemy antiaircraft fire, 527 sorties flown from the ten American CVs and CVLs demolished Japan's naval air power by sinking Chitose, Chiyoda, Zuiho, and Zuikaku. Heroic action by Hellcats and Avengers launched from 18 escort carriers helped turn back the enemy battle fleet and averted an American catastrophe in this last major fleet action of World War II.

Conclusion

The Battle of Leyte Gulf marked the end of Japan as a naval power. Subsequently, the American fast carrier task forces carried the war to the Japanese islands themselves, sending thousands of bombing sorties against a myriad of land targets.

Besides those carrier vs. carrier battles described in this article, the U.S. flattops supported numerous amphibi- ous landings as the Marines and Army island-hopped across the Pacific. The carriers sustained numerous losses during these operations, especially at the hands of the kamikaze suicide pilots off Okinawa. The development of radar- guided night fighter groups of Hellcats and Corsairs, such as those operated on the Independence as a night-fighter carrier at Leyte Gulf, inhibited the nocturnal activities of both suicide and conventional intruders. But it is clear that the mastery of aircraft carrier tactics and the production of huge numbers of ships, airplanes, and trained aircrew were the dominant factors in the American victory in the Pacific.

Bibliography

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