One Hundred Years of U.S. Navy Air Power (42 page)

In March 1942 the General Board formally proposed building a big carrier based on CV-E with an armored flight deck, arguing that such tough ships were essential. She would be so massive that she could support the larger aircraft then being bought, such as the Grumman F7F Tigercat (which had been conceived, however, to operate from
Essex
-class carriers). This U.S.-style armored flight-deck carrier was soon called the Type B Carrier (CV Type B, then CV-B, and finally CVB, the B often interpreted as “Big” or “Battle”). Six of these
Midway
-class CVB were projected, but three were cancelled at the end of the war.

The British managed to incorporate the heavy armored hangar by making it integral with their hull. U.S. designers could not adopt any such practice, so one great problem in the
Midway
design was how to support the vast weight of a deck treated as a superstructure. One lesson for the designers was never to do that again; in postwar carriers the flight deck was integral with the hull. It was a great triumph of U.S. structural design that large openings could be cut in the ship's side (to provide something like an open hangar) despite the integral-deck structure. The sheer weight of the armored deck made it necessary to reduce freeboard, so the
Midway
-class carriers were far wetter than the
Essexe
s. Another problem was how to provide some protection along the sides of the hangar, since surely an enemy would try to get weapons under the armored flight deck. No good solution presented itself, but the partial one was to place the ship's 4-inch guns in protected mounts along the sides of the hangar deck, so that there was a good chance that any weapon fired at the hangar would hit them instead. As a consequence, these ships had clearer flight decks than the
Essex
class.

In 1945 U.S. and British fleet carriers operated together in the face of Japanese kamikazes. U.S. officers noticed that kamikaze hits usually put their ships out of action (although many were repaired in forward areas). They considered the British armored-deck ships far superior, the saying being that after a hit they simply manned sweeps and cleaned up their flight decks. The British saw things very differently. They were painfully aware of how limited their aircraft capacity was and of how their aircraft could not be warmed up in their closed hangars (which were treated like magazines). When the British began to design a new carrier in 1943, they compared open- and closed- (armored) hangar designs. Eventually they selected a U.S.-style open hangar for their final wartime carrier design, HMS
Malta
. The ship was cancelled at the end of World War II, so until records were opened it was not clear just how impressed the British had been with U.S. design practices.

CONVERSION

The British developed another new carrier idea, a converted merchant ship to work with convoys. U-boats had to spend much of their time on the surface, submerging (if at all) only when near their targets. Only when surfaced could they develop sufficient sustained speed to shadow and then to intercept a convoy (very late in World War II the Germans introduced the snorkel, and the situation changed). Aircraft working with a convoy could catch surfaced U-boats. As yet there was no way that aircraft could detect submerged submarines, but the ability to frustrate U-boats trying to intercept a convoy was well worthwhile. British carrier operating practice had produced low-performance aircraft like the Swordfish torpedo bomber, which could operate even from a slow carrier with a small flight deck. By the time the British had their first converted merchant ship carrier (escort carrier), the U.S. Navy was working with the Royal Navy, although the United States was not yet at war. The U.S. Navy had no low-performance bombers, but it became interested in operating auto-gyros (predecessors of helicopters) from a converted merchant ship with a short flight deck. It converted a new freighter into the prototype escort carrier
Long Island
. By this time the U.S. Navy also had the new hydraulic catapult conceived for fleet carriers.
²⁹
These catapults made it possible to operate standard U.S. carrier aircraft from a converted merchant ship. Initially the new low-performance carriers were considered auxiliaries, designated AVG (seaplane tenders were AVs); later they were designated auxiliary carriers (ACV) and finally escort carriers (CVE). Late in 1941 the nominal U.S. requirement was twenty-five, soon cut to sixteen (with fifteen already under contract).
³⁰
The British were allocated another thirty, tentatively designated BAVGs, to be provided under Lend-Lease. Four more conversions were ex-tankers (
Cimarron
class), making a total of fifty such ships.
³¹

The
Cimarron
conversion was quite attractive, because it was larger than a C-3 and offered oil fuel for accompanying ships. The maximum effort program planned in 1942 (for 1943–1944) therefore included another twenty-four such ships, to be built as carriers from the keel up. None of these
Commencement Bay
–class ships was ready for combat before the end of the war, but they were used postwar. The earlier ships were reduced postwar to subsidiary roles, the most interesting of which were conversion of
Thetis Bay
into a prototype helicopter assault ship and conversion of
Gilbert Islands
into a communications relay ship (AGMR). In 1942 Henry Kaiser, who was already mass-producing Liberty ships on the West Coast, offered to build escort carriers designed as such from the keel up. The resulting
Casablanca
class was based on a Maritime Commission design for a small passenger ship (had it really been conceived as a carrier from the keel up, the design would have taken far too long). Fifty were built under a program authorized by President Roosevelt (hence not negotiated within the naval staff). Taking into account U.S. ships built for the Royal Navy, well over a hundred escort carriers were completed during World War II.

Conversion did not produce a particularly efficient carrier. The merchant ships were short and slow. Their holds were ill-suited to the shops and other facilities a carrier needed. Carrier facilities were far lighter than the usual cargoes, so the ships had to be ballasted heavily. The island was cut to a bare minimum, smoke pipes being led up alongside the flight deck. This very austere conversion, however, could be carried out rapidly, and in 1942 it was urgent to produce ships to fight the Battle of the Atlantic.

By 1943 the role of U.S. escort carriers had changed dramatically. To fight its war, the U-boat command had to maintain communications with all boats at sea. It directed them to targets, and it needed their reports of, for example, their fuel status and how many torpedoes remained. The Germans thought that their codes were secure and that reports from U-boats, using high-frequency (HF) radio could not be intercepted and certainly could not be subject to radio direction-finding. They were wrong on both counts. Code-breaking and radio direction-finding provided the Allied navies with what amounted to wide-area ocean surveillance of the U-boat force. In May 1943 the U.S. Navy began using this information to hunt down U-boats, rather than merely to screen convoys. Hunter-killer groups built around escort carriers attacked groups of U-boats whose position had been revealed by code breaking. Their aircraft ran down the shorter-range directions provided by the carriers' HF direction finders. The U.S. offensive was unpopular with the British, who feared that the Germans would realize that their codes had been broken, but it proved quite successful (and the Germans never realized why). The U.S. Navy became interested in offensive ASW based on ocean surveillance, an important idea postwar.

In the Pacific, escort carriers were used to ferry replacement aircraft (including Army aircraft for landings) and also to support the Marines directly in the later island battles.

By fall 1941, it seemed obvious that the United States would need many more fleet carriers. An
Essex
would probably take three years to build. Any rapid expansion would have to exploit ships whose hulls had already been laid down. Fortunately the high performance built into new naval aircraft and the new catapults dramatically reduced the requirements any such converted carriers would have to meet. By 1941 the U.S. Navy was building numerous 10,000-ton
Cleveland
-class light cruisers. A study of a full carrier conversion showed that it would be both inefficient and lengthy. The idea was resisted by the General Board.
³²
After war broke out, the idea was reconsidered on the basis of the existing escort carriers. This time it seemed well worthwhile, and nine ships were converted into
Independence
-class light carriers (CVL). As measured by the number of aircraft per ton, they were far less efficient than the big
Essex
, but they were still a very useful expedient (the typical air group was twelve fighters, nine bombers, and nine torpedo bombers). Typically one light carrier worked with three fleet carriers in a task group. Once the night carrier concept had been developed, a light carrier offered a full complement of night fighters without complicating the operation of the big strike carriers. The light carrier was considered so attractive that late in the war two ships (
Wright
and
Saipan
) were designed from the outset for this role, using adapted heavy cruiser hulls (which had not been laid down as heavy cruisers).

TRANSITION

The period through 1945 produced a particular type of carrier for both strategic and technological reasons. The strategic reason was that, through this period, the U.S. Navy was designed to seize and then exploit sea control. It was therefore conceived much more to attack an enemy navy—the Imperial Japanese Navy—than to strike at land targets. Aircraft were shaped by that requirement. It was entirely reasonable to expect a dive- or torpedo bomber to take off within the 400-foot length available forward of parked aircraft. U.S. naval aircraft were expected to attack some land targets, particularly when supporting Marines going ashore, but that was very much a secondary role. Perhaps it should be added that even after the Royal Navy regained direct control of its fleet air arm in 1939, it still had to avoid encroaching on the land attack role espoused by the Royal Air Force; there really was a distinct U.S. Navy view of the role of naval aviation. That view would become very important after 1945. In 1945, all existing U.S. naval aircraft could operate from all existing carriers. By 1945 the U.S. Navy was interested in larger carrier aircraft, such as the twin-engine Grumman F7F Tigercat, which would not have been able to operate from
small carriers; but it was still true that carrier dimensions and speed shaped naval aircraft, not the other way around. It is not, incidentally, true that some aircraft, such as the Tigercat, were conceived specifically to operate from the big
Midway
s—they had not yet been designed when the aircraft specifications were laid out.

The foundation built between the wars made it possible for the U.S. Navy to shift toward a carrier-centered World War II fleet. The huge prewar U.S. naval air establishment was relatively easy to expand to train tens of thousands of new pilots and other personnel. It also trained the senior officers to command a much-expanded carrier fleet. In 1941 the U.S. Navy had seven fleet carriers and one escort carrier. By the end of the war, the U.S. Navy had over a hundred carriers (although most were quick and relatively inefficient conversions of merchant ship and cruiser hulls).

By the time the Imperial Japanese Navy was essentially gone, in 1945, the U.S. Navy had become interested in a new mission, strategic air attack. It was not entirely new: prewar fleet exercises did show valuable potentials for supporting amphibious landings and for attacking enemy shore installations (the U.S. carriers often raided the Panama Canal, Pearl Harbor, and Los Angeles), but they were secondary.

That year the U.S. naval staff studied the contribution that carrier aircraft could make to the bomber attack on Japan by B-29s. It concluded that given the sheer number of carrier aircraft, and the short ranges from which they could be launched, carrier bombers could deliver up to 60 percent of the tonnage available from B-29s. Against this calculation, a January 1945 carrier raid on Tokyo was less than successful, the small carrier bombers finding the high winds over Japan too great a hindrance and probably also finding it difficult to identify targets from the high altitudes then used. They might have performed differently a few months later, when the heavy bombers shifted to incendiary raids mounted from relatively low altitudes. In that case the sheer number of carrier bombers might have made Japanese defense far more difficult. The other advantage of carrier attack was that a carrier could mount attacks from a far wider arc, making it much more difficult for a defender to guess where to place defenses.

Navy interest had probably been spurred by the April 1942 Doolittle Raid, when USS
Hornet
launched sixteen Army B-25 medium bombers to attack Tokyo. They did relatively little damage, but the raid convinced the Japanese that they had to destroy the U.S. carrier force. Their attempt to force a decisive battle, at Midway that June, proved disastrous for them: they lost four carriers, which their limited industrial base could not easily replace. U.S. industrial capacity could more than replace the carriers lost in 1942; newly built U.S. warships dominated the Pacific War from 1943 on. Even before the Doolittle Raid (but probably inspired by planning for it) the U.S. Navy was sponsoring a Grumman design for a carrier-based medium bomber comparable to a B-25 (the TB2F). Although this project died in April 1944 (surprise air attacks were unlikely to succeed now that the Japanese had early warning radar),
the idea of heavy land attacks mounted from carriers became very important postwar, largely shaping the new carriers.