WWII: How the U.S. Navy Shattered Japan's Aircraft Carrier Fleet

June 23, 2020 Topic: History Region: World Blog Brand: The Reboot Tags: World War IIPacific TheaterJapanAircraft Carriers

WWII: How the U.S. Navy Shattered Japan's Aircraft Carrier Fleet

The battle was nicknamed the Great Marianas Turkey Shoot.

One invasion was headed for Normandy in France. The “other” invasion was headed farther, a 10-day voyage from Hawaii and other bases to Saipan, an island 1,200 nautical miles from Tokyo, 12 miles long and 46.5 square miles in area. Once taken, it would provide the U.S. Army Air Forces with a base for the huge Boeing B-29 Superfortress bombers to pound Tokyo. Also up for invasion in the same attack were Saipan’s neighbors, Tinian, and a small piece of American soil that had been violated since Pearl Harbor, the island of Guam, under Japanese occupation for three long years.


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Seizing the Northern Marianas would thus redeem American honor. It would also signal to Japan that the Empire’s main defense line had been breached and force the Combined Fleet to emerge from two years of hibernation and training to fight the decisive battle against the Americans to save that Empire—the biggest carrier battle yet fought and one of the most decisive naval battles in history.

A New Generation of Ships and Planes

By 1944, the American counterattack against Japan’s aggression was in full flood. The losses at Pearl Harbor and thereafter had been made good with what was virtually a new navy and air force, and a series of invasions had taken the Gilbert and Marshall Islands from the Japanese.

Indeed it was a new navy. Of the 15 carriers lined up at Majuro Atoll under Vice Admiral Raymond A. Spruance, only one predated Pearl Harbor—the venerable USS Enterprise, with a battle record unmatched in nearly any navy. The battleships, cruisers, and destroyers that escorted “Murderers’ Row” were also relatively new, fast ships that bristled with antiaircraft guns and electronics unheard of before the war.

The aircraft were from a new generation as well, powerful Grumman TBF Avenger torpedo bombers and massive Grumman F6F Hellcat and Vought F4U Corsair fighters, which could run rings around Japan’s Zeros with their powerful engines. The ships’ very names showed America’s resilience. Four of the aircraft carriers, LexingtonHornetWasp, and Yorktown, all bore the names of American carriers sunk in 1942.

Yet the old ships were still there—one of them, the heavy cruiser USS Indianapolis, known to her crew as the “Indy Maru,” doubled as Spruance’s flagship. The battleships that endured bombing at Hawaii were back as well, too slow to form the primary battle line but loaded with high explosive shells for shore bombardment. Spruance’s 5th Fleet was a huge organization, but at its core was Task Force 58, under Vice Admiral Marc Mitscher, flying his flag on the Lexington. Mitscher commanded 15 fleet and light carriers, seven fast battleships, 12 escort carriers, 11 cruisers, and 91 destroyer escorts. Covering this force were nearly 900 aircraft.

Spruance, the boss of the entire 5th Fleet, was no aviator, but he had already won the greatest air-naval battle of them all, America’s incredible victory at Midway. Cool, quiet, described as a “patient fox,” he used caution to plot the deadly Midway ambush. Now he was leading a huge fleet on a massive offensive on Saipan, Tinian, and Guam.

Ozawa’s Powerful Naval Force

He may have known it from radio intercepts and codebreaking, but Spruance gave no inkling that he was interested in the fact that the commander of the Japanese garrison on Saipan was an old enemy, Vice Admiral Chuichi Nagumo, who had led the attack on Pearl Harbor and been defeated at Midway.

But Nagumo was not leading Japan’s naval riposte to the American invasion, now steaming down on Saipan. That job was in the hands of Vice Admiral Jisaburo Ozawa, regarded as the Empire’s best carrier admiral. Commanding the Mobile Fleet, his situation was becoming increasingly critical. While the U.S. Navy grew in strength, his navy was slowly being whittled away. Japanese dockyards and training schools could not keep up with American industry and technical skill. American submarines, having overcome torpedo deficiencies, were cleaning the seas of Japanese tankers, strangling the homeland and denying the Imperial Navy vital fuel.

To fight the battle, the Imperial Navy had moved the carrier force to Singapore, close to its oil stocks in Java and Borneo. The Borneo crude oil was of such high quality that it could be pumped straight into the Imperial Navy’s bunkers without refining. However, the unrefined sulfur-ridden Borneo crude could damage the Navy’s pipes, and more importantly, was even more flammable than the refined variety.

None of this mattered to Ozawa. His brief was to defeat the Americans, and even if that meant his ships would all have to get major engine repairs after the battle, he would fight hard with what he had. The plan was called Operation A-Go, and it was activated shortly after the U.S. Fleet arrived off Saipan on June 8, to start softening up the island.

Operation A-Go called for the Japanese to hit the Americans with everything they had as soon as the American objective had been determined and destroy the enemy with one blow.  To do so, the Japanese had some high cards to play. First were Ozawa’s eight carriers, which included his flagship, the powerful new Taiho, a 34,000-ton behemoth, the largest carrier afloat and Japan’s first with an armored flight deck. She carried 60 aircraft.

Behind her were the last two veterans of Pearl Harbor, Shokaku and Zuikaku, sisters at 29,800 tons each, carrying 80 aircraft apiece. Behind these three tough warriors were two smaller carriers, the Hiyo and Junyo, both converted liners weighing 26,949 tons, carrying 53 aircraft each. With four more light carriers, ChitoseChiyodaZuiho, and Ryuho, Ozawa could sortie 450 aircraft—much fewer than his American counterpart, but still the largest carrier-based air force Japan would ever deploy.

Ozawa also had 540 land-based aircraft scattered on airfields across the Pacific with orders to concentrate on Saipan and the Marianas. He also had something new for Japan, giman-shi, or deceiving paper, better known to the British as “window” and the Americans as “chaff,” metallic paper that would jam American radar screens.

The planes were also tough, if outdated. The main fighter was still the Mitsubishi A6M5 Zero, while the primary torpedo bombers were the older B5N Kate from the Pearl Harbor glory days and the newer B6N Jill, both from Nakajima. The dive-bomber of choice was the modern Yokosuka D4Y1 Judy, which sported retractable landing gear and a Daimler-Benz engine, backed up by the venerable Aichi D3A1 Val. One fatal weakness was evident. While American aviators had up to 400 hours flying time, some Japanese pilots had as little as 20 in their logbooks.

Behind the Japanese carriers came a powerful force: the two of the largest battleships ever built, Yamato and Musashi, equipped with nine 18-inch guns each; the slower Nagato, with 15-inch guns; and the powerful and fast battleships Haruna and Kongo. Seven heavy cruisers and one light cruiser backed up the dreadnoughts, along with 19 destroyers.

Smashing Saipan, Tinian, and Guam

The key to the Japanese plan was the 500-odd aircraft on its ground bases, which would attack the Americans initially and whittle down their air umbrella, enabling the surface ships and carriers to punch out the American carriers and battleships, leaving the American transport fleet open to attack.

The American invasion of the Marianas would require their fleets to sail as far as 1,017 miles from their anchorage at Eniwetok, and as far as 3,500 from Hawaii. More than 535 ships loaded with 127,571 troops sortied from a variety of ports, with the assault set for June 15. The invasion was code-named Forager.

Nagumo’s defenses were formidable. The 21st Army, under Lt. Gen. Yoshitsugu Saito, fielded about 31,629 men which included 6,690 Navy men, including a tough 800-man Special Naval Landing Force regiment and naval guard force of 400 men. They were equipped with eight Whitworth-Armstrong 6-inch guns, nine 140mm guns, eight 120mm guns, four 200mm mortars, and a collection of bunkers, pillboxes, and machine guns.

Task Force 58 sailed from Majuro at Eniwetok in early June amid a steady drizzle. Under the gray skies, 96,618 men crewing 111 U.S. warships painted in dazzle camouflage steamed from the anchorage at two-minute intervals. It took the whole task force five hours to sortie and shuffle into antisubmarine formation. Behind them came the bombardment forces and transports.

On June 11, the 15 American carriers got to work pulverizing the Japanese defenses, hurling more than 200 fighters and torpedo bombers against Saipan and Tinian. The senior American carrier air unit was CVG-10, based on USS Enterprise. Under its ebullient boss, Commander William R. “Killer” Kane, CVG-10 was a well-trained veteran outfit, which included a night-fighting group of F4U Corsairs. That day Kane led 58 Hellcats against Saipan.