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How the US Navy Sunk the Shinano (Japan’s Battleship Turned Aircraft Carrier)

Among the vessels lost during the war was the Imperial Japanese Navy’s Shinano, the largest carrier built during the Second World War.

INJ Aircraft Carrier Shinano. Image Credit: Creative Commons.
INJ Aircraft Carrier Shinano. Image Credit: Creative Commons.

Shinano: The Death of the First “Supercarrier” – During the Second World War, the Empire of Japan produced 30 aircraft carriers, including 11 heavy or fleet carriers.

Four of those – including Akagi, Kaga, Sōryū and Hiryū, part of the six-carrier force that had attacked Pearl Harbor on December 7, 1941, were sunk at the Battle of Midway in June 1942.

Two of the other fleet carriers, Shōkaku and Zuikaku participated in every major naval action of the Second World War with the exception of Midway, were also sunk by U.S. warships.

In fact of those 11 heavy carriers built during the war, only the Unryū-class carrier Katsuragi survived the war. She was used as a repatriation transport for a number of months following the war and was scrapped in Japan in late 1946.

Among the vessels lost during the war was the Imperial Japanese Navy’s Shinano, the largest carrier built during the Second World War. She had been laid down in May 1940 as the third Yamato­-class battleship, but after the loss of those four fleet carriers at Midway, a decision was made to convert her to a carrier to replenish the lost naval aviation strength.

That decision was not without issues, however. She had been about 45 percent completed and was twice as big as the previous fleet carriers including the Akagi. At 72,000-tons, Shinano was the world’s first “supercarrier” – she was 870 feet long, and her flight deck was armored against the largest of the air-dropped armor-piercing bombs, while she was also equipped with a belt of armor at the waterline and had a network of internal watertight doors to protect her from torpedoes. The immense hanger of the carrier had room to carry 150 combat aircraft, including two-engine medium bombers.

Knowing that a massive carrier would be a massive target, the Japanese installed sixteen 5-inch anti-aircraft guns and almost 150 25mm cannons. She utilized the same engines as the battleships Yamato and Musashi and had a top speed of 27 knots and a range of 10,000 nautical miles. The plan was that this supercarrier could turn the Imperial Japanese Navy into an effective fighting force again, and turn the tide of the war back to Japan’s favor.

However, her construction was time-consuming. Whereas the United States was rolling out warships at a blistering pace, the Shinano’s conversion from battleship to carrier was not completed until November 1944. Moreover, Japan lacked the aircraft – not to mention the pilots – for the ship’s air wing. In addition, nearly all of the IJN’s outer defensive circle was destroyed and American B-29s were already in range of Japanese cities.

Simply put, the carrier may not have been “too little” but it was certainly “too late” to make any significant difference. The war wasn’t over, but for Japan it was already lost.

Then the Japanese made a fateful and questionable decision. Instead of using the Shinano as a fleet attack carrier, she was to serve as a floating airbase for the repairing, transfer and maintenance of the massive fleet of Kamikazes.

As the U.S. Army Air Forces had begun bombing Tokyo, it was decided to transfer the warship to the naval base at Kure. This was actually resisted by her Captain, Toshio Abe, who expressed concern that while the flight deck and hull were finished, the internal structure was incomplete. Only half the engines were actually in working order, while those planned watertight doors were not installed – nor were fire-suppression systems at the ready.

Yet, the IJN admirals insisted that the warship was Japan’s only hope. She departed Japan on November 28, 1944, carrying about 2,500 men on board along with six Shinyo special attack boats and 50 Ohka special attack rocket aircraft. The supercarrier was escorted by three IJN destroyers, Isokaze, Yukikaze, and Hamakaze.

Just three hours after leaving port, Shinano was spotted by United States Navy Balao-class submarine USS Archerfish (SS/AGSS-311), which was on her fifth patrol under the command of Commander Joseph F. Enright. The sub’s primary mission had been to provide lifeguard services for the first B-29 Superfortress strikes against Tokyo, but received word that there would be no air raids launched that day. Instead, she was given the green light to roam the waters looking for Japanese targets. However, the crew of the boat didn’t realize what they sighted.

The submarine was also spotted by the carrier, but believed it to be part of an American “wolf pack.” Abe made the decision to zig-zag to avoid shots from other submarines. That proved to be a fatal mistake, as Archerfish was alone and wouldn’t have been able to catch the carrier alone.

The submarine was given an unbelievable opportunity.

Believing it to be a large tanker, the U.S. submarine fired six torpedoes and four hit the target. The first hit destroyed the ship’s refrigerated areas and one of the empty aviation gas storage tanks, while the second flooded the outboard engine room. The third torpedo destroyed the No. 3 fireroom, and the fourth flooded the starboard air compressor room, magazines, and ruptured the starboard oil storage tank.  With no countermeasures to stop it, water poured in and the ship was doomed.

Efforts were made to maintain speed before a second attack run could be commenced, but it didn’t matter. The carrier began to list, and damage control efforts were inadequate. While the carrier didn’t immediately sink, the situation was hopeless. Abe attempted to have the destroyers tow the carrier towards shore with a hope to beach her, but she was overweight at that point from the water the carrier had taken on. The captain finally ordered the ship abandoned. Still, 1,435 of her sailors were killed – among them Captain Abe. She was the largest warship ever sunk by a submarine.

The news of the loss of Shinano was kept a secret, with the survivors of the crew quarantined for months to prevent the news from leaking. The U.S. Office of Naval Intelligence first believed Archerfish had sunk a cruiser, and after Commander Enright made sketches of the ship, the submarine was given credit for sinking a 28,000-ton carrier. It wasn’t until after the war that it was learned that it had been the sister ship of Yamato.

Japanese secrecy was so great the United States didn’t even know it was being built. Archerfish received the Presidential Unit Citation, and Enright was awarded the Navy Cross.

Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers and websites. He regularly writes about military small arms, and is the author of several books on military headgear including A Gallery of Military Headdress, which is available on

Written By

Expert Biography: A Senior Editor for 1945, Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers, and websites with over 3,000 published pieces over a twenty-year career in journalism. He regularly writes about military hardware, firearms history, cybersecurity, and international affairs. Peter is also a Contributing Writer for Forbes. You can follow him on Twitter: @PeterSuciu.