Shinano

1. Lead

The Shinano was the largest aircraft carrier of the Second World War, and one of the strangest warships ever built: a battleship of the Yamato class, the largest battleships in history, that was converted halfway through construction into an aircraft carrier, and that was sunk by an American submarine only ten days after it entered service, on its first voyage, without ever launching an aircraft in combat. At about 65,000 tonnes standard displacement and 266 metres long, the Shinano was larger than any other aircraft carrier in the world until the 1950s, and it remains the largest warship ever sunk by a submarine. Its story is a story of improvisation, of desperation and of waste: of a navy that had lost its carriers at Midway and that tried to replace them by converting a battleship, of a ship that was rushed into service before it was finished, and of a crew that died because the ship’s watertight doors were not yet fitted and because its damage control was not yet organised. The Shinano never fought a battle, but its sinking, on 29 November 1944, is one of the most famous submarine actions of the war.

2. Key Facts

Type	Aircraft carrier (converted from a Yamato-class battleship hull)
Origin	Japan
Designer	Imperial Japanese Navy (Captain Kikuo Fujimoto’s Yamato design, adapted)
Builder	Yokosuka Naval Arsenal
Laid down	4 May 1940 (as a battleship)
Launched	8 October 1944
Commissioned	19 November 1944
Sunk	29 November 1944, by the submarine USS Archerfish
Displacement	About 64,800 tonnes standard; about 71,900 tonnes at full load
Length	266 m
Beam	36.3 m
Draught	About 10.3 m
Propulsion	12 Kampon boilers; 4 steam turbines; 150,000 shp; 4 shafts
Speed	27 knots (about 50 km/h)
Range	About 10,000 nautical miles at 18 knots (estimated)
Complement	About 2,400 officers and men (about 2,515 aboard when sunk)
Aircraft carried	47 operational aircraft (designed capacity; up to about 120 in reserve as a support carrier)
Armament	16 × 127 mm anti-aircraft guns; 145 × 25 mm anti-aircraft guns; 12 × 120 mm rocket launchers
Armour	Belt 160–200 mm (battleship armour retained); flight deck 75–80 mm (armoured)

3. Background and Development

A Yamato Battleship

The Shinano began its life as the third battleship of the Yamato class, the largest battleships ever built. The Yamato class was designed in the 1930s, when the Imperial Japanese Navy believed that the decisive battle of a future war would be fought by battleships, and the Yamato and her sister Musashi, each armed with nine 460 mm guns — the largest naval guns ever mounted on a ship — were the expression of that belief. The third ship of the class, which was to have been named Shinano after the old Shinano Province, was laid down at the Yokosuka Naval Arsenal on 4 May 1940. Work on the hull proceeded slowly, because the Japanese shipbuilding industry was stretched by the demands of the war, and by 1942, when the ship was about half complete, the war had changed: the battleship was no longer the decisive weapon, and the aircraft carrier was.

Midway and the Decision to Convert

The Battle of Midway, in June 1942, was the turning point. In a single day, the Japanese Navy lost four of its six fleet aircraft carriers — Akagi, Kaga, Soryu and Hiryu — and with them the core of its naval air power. The loss was irreplaceable in the short term, because Japan could not build new fleet carriers quickly, and the Navy’s response was to convert ships that were already under construction. The Shinano, whose hull was about half complete, was the obvious candidate: her great size would make her the largest carrier in the world, and her battleship armour would make her far more resistant to damage than any other carrier. In June 1942, after Midway, the Navy ordered the Shinano’s conversion to an aircraft carrier, and work on the battleship was stopped. The conversion was a major undertaking: the battleship’s armoured citadel was retained, the 460 mm gun turrets were never installed, and a flight deck, a hangar and the machinery for handling aircraft were built on top of the hull.

A Support Carrier, Not a Fleet Carrier

The Shinano was not designed to be a fleet carrier, like the Akagi or the American Essex class. She was designed to be a support carrier — a floating base that would carry replacement aircraft, fuel and spare parts to the fleet carriers, and that would repair damaged aircraft and return them to service. Her designed air group was only 47 operational aircraft, although she could carry many more in reserve in her hangars, and her flight deck, although it was armoured, was shorter than that of a fleet carrier. The concept reflected the Japanese Navy’s desperate situation in 1943–44: it could not build enough fleet carriers, and it hoped that a support carrier, protected by battleship armour, could keep its remaining carriers supplied and fighting. The Shinano’s conversion was slow, because the shipyard was short of labour and of materials, and because the design was changed several times during construction. She was launched on 8 October 1944, and she was commissioned on 19 November 1944, before she was finished, because the Navy needed her at Kure, where her fitting-out was to be completed.

4. Design

The Battleship Hull and Armour

The Shinano’s design was dominated by her origin as a battleship. Her hull was the hull of a Yamato-class battleship, 266 metres long and 36.3 metres wide, with the thick armour belt of a battleship — 160 to 200 mm of armour on the sides — and with the underwater protection of a battleship, designed to resist torpedoes. Her flight deck was armoured with 75 to 80 mm of steel, which was intended to protect the hangar below from bombs, and her hangar was divided into sections by fireproof bulkheads. The Shinano was, on paper, the most heavily protected aircraft carrier in the world, and her designers believed that she could survive damage that would sink any other carrier. The belief was wrong, as the ship’s sinking would show: the armour protected her against bombs and against shells, but it could not protect her against torpedoes that flooded her compartments, and her watertight integrity — the system of doors and bulkheads that keeps a flooded compartment from flooding the next — was not yet complete when she sailed.

The Flight Deck and the Air Group

The Shinano’s flight deck was 256 metres long and 36 metres wide, and it was served by two aircraft lifts. Her hangar was large enough to hold about 120 aircraft in reserve, although her operational air group was only 47 aircraft — a mixture of Mitsubishi A6M Zero fighters, Yokosuka D4Y dive bombers and Nakajima B6N torpedo bombers, in the proportions of a fleet carrier’s air group. The ship’s aircraft handling arrangements were modern, with a crash barrier, with arrester wires and with a catapult, but they were never tested in service, because the Shinano never operated aircraft in combat. The ship’s island — the superstructure on the starboard side that housed the bridge and the funnel — was small, because the ship’s designers wanted as much flight-deck space as possible, and the funnel was angled outwards to keep smoke away from the flight deck. The Shinano’s air group was never embarked: when she sailed on her first and last voyage, she carried no aircraft at all, only the shipyard workers who were still fitting her out.

Propulsion and Anti-Aircraft Armament

The Shinano was powered by 12 Kampon boilers and 4 steam turbines, producing 150,000 shaft horsepower and driving 4 propellers, which gave her a top speed of 27 knots — slower than a fleet carrier, but fast enough for a support carrier. Her anti-aircraft armament was heavy: 16 127 mm dual-purpose guns in eight twin mounts, 145 25 mm anti-aircraft guns in single, twin and triple mounts, and 12 120 mm rocket launchers, which fired a barrage of rockets at attacking aircraft. The 25 mm gun, which was the standard Japanese light anti-aircraft weapon, was inadequate against the fast American aircraft of 1944, and the Shinano’s anti-aircraft armament, although numerous, was not effective enough to protect her against a determined air attack. In the event, she was never attacked from the air: she was sunk by a submarine, against which her anti-aircraft guns were useless. Her underwater protection, which was the protection of a battleship, was her best defence, and it was defeated by four torpedoes.

5. Variants

The Three Yamato Sisters

Ship	Type	Laid down	Completed	Fate
Yamato	Battleship	1937	1941	Sunk by American aircraft, 7 April 1945
Musashi	Battleship	1938	1942	Sunk by American aircraft, 24 October 1944 (Battle of Leyte Gulf)
Shinano	Battleship converted to aircraft carrier	1940	1944	Sunk by the submarine USS Archerfish, 29 November 1944
Hull No. 111 (fourth ship)	Battleship (cancelled)	1940	Never completed	Construction stopped in 1942; hull scrapped

The Shinano was the only one of the Yamato class to be converted to an aircraft carrier, and the only one of the three sisters to be sunk by a submarine. Her sisters, Yamato and Musashi, were completed as battleships, and both were sunk by American carrier aircraft — Musashi at Leyte Gulf in October 1944, and Yamato in April 1945, on her final mission to Okinawa. The fourth ship of the class, Hull No. 111, was laid down in 1940 and cancelled in 1942, and her hull was scrapped. The Shinano’s conversion was therefore unique: she was the only Yamato-class hull to be completed in a form other than that for which she was designed, and she was the only one to be sunk before she had ever fought a battle. The three sisters are often discussed together, because they were the largest warships ever built, and because all three were sunk within six months of each other, between October 1944 and April 1945.

The Conversion and Its Limits

The Shinano’s conversion imposed limits that no fleet carrier had. Her hangar was divided by the battleship’s armoured bulkheads, which made the handling of aircraft slower and more difficult, and her flight deck, although armoured, was shorter than that of a fleet carrier of comparable size. Her designed air group of 47 aircraft was small for a ship of her size — an American Essex-class carrier, which was smaller, carried about 90 aircraft — and her speed of 27 knots was slower than the 33 knots of an Essex. The conversion was a compromise, and it showed: the Shinano was a battleship that had been made into a carrier, not a carrier designed from the start, and her designers had to accept the limitations of the hull they had been given. The Japanese Navy accepted those limitations, because it had no alternative: it could not build a new fleet carrier in the time available, and the Shinano, for all her faults, was the largest carrier it could put to sea.

6. Operational History

The First and Last Voyage

The Shinano’s operational history is the shortest of any major warship of the Second World War: ten days, from her commissioning on 19 November 1944 to her sinking on 29 November 1944, and a single voyage, from Yokosuka to Kure. She was commissioned before she was finished, because the Navy wanted her at Kure, where her fitting-out was to be completed in the relative safety of the Inland Sea, away from the American submarines that were patrolling off Yokosuka. She sailed from Yokosuka on the evening of 28 November 1944, escorted by three destroyers — Isokaze, Hamakaze and Yukikaze — and carrying, in addition to her crew of about 2,400, about 100 shipyard workers who were still working on her, and a number of naval personnel being transferred to Kure. She carried no aircraft, her watertight doors were not yet fitted, her pumps were not yet installed, and her crew, many of whom had never been to sea, had not yet been trained in damage control.

The Attack of the USS Archerfish

The Shinano was sunk by a single submarine, the USS Archerfish, in one of the most famous submarine attacks of the Second World War. The attack, which took place in the early morning of 29 November 1944, was the work of Commander Joseph F. Enright, who had followed the Shinano through the night and who fired six torpedoes at her from a range of about 1,300 metres. Four of the torpedoes hit, and the Shinano, which was unfinished and whose crew had not been trained in damage control, sank seven hours later. The two sections below describe the submarine and her commander, and the slow sinking that followed the attack.

The Archerfish was a Balao-class submarine, one of the most successful classes of submarine in the war, and her commander, Joseph Enright, was an experienced officer who had already served in the Pacific. The attack on the Shinano was Enright’s first great success, and it was achieved by patience: he followed the Japanese force through the night, he waited for the Shinano to turn, and he fired when the range was short and the target was broadside.

The Submarine and Its Commander

The submarine that sank the Shinano was the USS Archerfish, an American Balao-class submarine commanded by Commander Joseph F. Enright. The Archerfish had been on patrol off Japan, and on 28 November 1944 she detected the Shinano and her escorts leaving Yokosuka. Enright followed the Japanese force through the night, and in the early morning of 29 November, when the Shinano turned south-east, he manoeuvred into a firing position. At 03:17, the Archerfish fired six torpedoes at the Shinano from a range of about 1,300 metres. Four of the torpedoes hit the carrier, on her starboard side, and the other two missed. The hits flooded the boiler rooms and the engine rooms, and the Shinano began to list to starboard. Enright, believing that he had sunk a cruiser — he did not know that his target was the largest carrier in the world — dived to escape the escorts’ depth charges, and the Archerfish survived the attack.

The Sinking

The Shinano’s sinking was slow, and it was caused as much by her unfinished condition as by the torpedoes. The torpedoes flooded four boiler rooms and an engine room, and the ship listed to starboard. The crew tried to counter-flood the port side to correct the list, but the watertight doors between the compartments had not yet been fitted, and the water spread from compartment to compartment. The pumps that should have removed the water had not yet been installed, and the crew, who had not been trained in damage control, did not know how to stop the flooding. The list increased steadily, and at about 10:00 the ship’s captain, Captain Toshio Abe, ordered the crew to abandon ship. The Shinano capsized and sank at about 10:57 on 29 November 1944, about seven hours after she was hit, with the loss of about 1,435 of the about 2,515 men aboard, including Captain Abe, who went down with his ship. The destroyers rescued about 1,080 survivors, including the shipyard workers and the naval personnel who had been aboard.

The Aftermath

The sinking of the Shinano was a disaster for the Japanese Navy, and it was kept secret from the Japanese public. The Navy did not announce the loss, and the families of the dead were not told how their sons and husbands had died. The American Navy, for its part, did not know what the Archerfish had sunk: Enright had reported sinking a cruiser, and it was only after the war, when the Japanese records were examined, that the Americans learned that the Archerfish had sunk the largest aircraft carrier in the world. Enright was awarded the Navy Cross for the action, and the Archerfish became one of the most famous submarines of the war. The Shinano’s sinking was the last great success of the American submarine campaign against Japan, and it showed, more clearly than any other single action, how the Japanese Navy’s desperate improvisation had failed. The Shinano’s sinking was also the last time that a warship of her size was sunk by a submarine, and her story is still studied by naval officers as an example of how a ship that is rushed to sea before she is ready can be lost to a single well-handled submarine.

7. Performance and Specifications

Specifications

Specification	Shinano
Displacement (standard)	About 64,800 tonnes
Displacement (full load)	About 71,900 tonnes
Length	266 m
Beam	36.3 m
Draught	About 10.3 m
Propulsion	12 Kampon boilers; 4 steam turbines; 150,000 shp
Speed	27 knots (about 50 km/h)
Range	About 10,000 nautical miles at 18 knots (estimated)
Complement	About 2,400 (about 2,515 aboard when sunk)
Aircraft (designed)	47 operational; up to about 120 in reserve
Flight deck	256 m × 36 m; 2 lifts
Armament	16 × 127 mm; 145 × 25 mm; 12 × 120 mm rocket launchers
Armour (belt)	160–200 mm
Armour (flight deck)	75–80 mm
Service life	10 days (19–29 November 1944)

The table shows the Shinano’s paradox: she was the largest aircraft carrier in the world, and she was also the shortest-lived. Her displacement of about 65,000 tonnes standard was greater than that of any other carrier of the war — the American Essex class displaced about 27,000 tonnes standard — and her length of 266 metres was greater than that of any other carrier. But her air group of 47 aircraft was smaller than that of an Essex, which carried about 90, and her speed of 27 knots was slower than the Essex’s 33 knots. The Shinano’s size was the size of a battleship, and her air power was the air power of a light carrier, and the mismatch between the two is the key to understanding her: she was a battleship’s hull with a carrier’s superstructure, and she was neither a good battleship nor a good carrier. The table also shows the Shinano’s cost in lives: about 1,435 men died when she sank, including her captain, and the loss was the greatest single loss of life in the sinking of a Japanese warship by a submarine.

Comparison with Other Carriers

Compared with the other aircraft carriers of the war, the Shinano was an outlier in every respect. The American Essex class, which was the standard American fleet carrier, displaced about 27,000 tonnes, carried about 90 aircraft and could make 33 knots; the Shinano displaced more than twice as much, carried about half as many aircraft and was six knots slower. The Japanese Taiho, which was Japan’s most modern fleet carrier, displaced about 29,000 tonnes, carried about 65 aircraft and could make 33 knots; the Shinano was more than twice as large, carried fewer aircraft and was slower. The British Illustrious class, which had armoured flight decks like the Shinano, displaced about 23,000 tonnes and carried about 36 aircraft; the Shinano was almost three times as large and carried only a few more aircraft. The comparison shows that the Shinano’s size was not an advantage: it was the size of a battleship, and it brought with it a battleship’s cost, a battleship’s crew and a battleship’s vulnerability to torpedoes, without bringing a battleship’s guns or a fleet carrier’s air power.

8. Operators

Japan Alone

The Shinano was used only by Japan, and only by the Imperial Japanese Navy, and she was in service for only ten days. She was never exported, never licence-built and never used by any other country, and she never operated aircraft in combat. Her crew was Japanese, her captain was Captain Toshio Abe, and her escorts on her final voyage were the Japanese destroyers Isokaze, Hamakaze and Yukikaze. The Shinano’s short service means that there is little to say about her operators: she was a Japanese ship, built in a Japanese shipyard, crewed by Japanese sailors, and sunk by an American submarine. Her story is a Japanese story, and it is told in Japan as a tragedy: the tragedy of a great ship that was never given a chance to fight, and of a crew that died because the ship was not yet ready for sea. The Shinano’s crew was a mixture of experienced sailors and of young recruits who had never been to sea, and the ship’s officers, who knew that she was not ready, had protested against sailing, but the Navy’s orders were absolute, and the ship sailed as ordered.

The American Submarine Force

The Shinano’s sinking was the work of the American submarine force, and above all of the USS Archerfish and her commander, Joseph Enright. The American submarine campaign against Japan was one of the most successful campaigns of the war: American submarines sank about 1,300 Japanese merchant ships and about 200 Japanese warships, and they strangled the Japanese economy by cutting off the oil, the food and the raw materials that Japan needed to fight. The sinking of the Shinano was the largest single success of the campaign, in terms of the tonnage sunk, and it was achieved by a single submarine, with four torpedoes, against a ship that was escorted by three destroyers. The Archerfish’s success showed the power of the submarine, and it showed the vulnerability of even the largest and most heavily armoured warship to a well-handled submarine. The American submarine force’s record in the Pacific is one of the great achievements of the war, and the sinking of the Shinano is its most famous single action.

9. Legacy and Influence

The Largest Warship Ever Sunk by a Submarine

The Shinano’s legacy is a record: she remains the largest warship ever sunk by a submarine, and she is likely to remain so, because no warship as large as she was is ever likely to be sunk by a submarine again. Her displacement of about 65,000 tonnes standard is greater than that of any other ship sunk by a submarine, and her sinking, by four torpedoes from a single submarine, is a demonstration of the submarine’s power that has never been equalled. The record is a melancholy one, because the Shinano never fought a battle and never launched an aircraft, and her sinking was not a victory over a fighting ship but the destruction of a ship that was not yet ready for sea. But the record stands, and it is the reason why the Shinano is remembered, above all, by submariners, who regard the Archerfish’s attack as one of the great submarine actions in history.

A Warning About Rushing Ships to Sea

The Shinano’s sinking is also a warning about the dangers of rushing an unfinished ship to sea. The ship sailed without her watertight doors, without her pumps, without her aircraft and without a trained crew, because the Navy needed her at Kure and because the American submarines off Yokosuka made every day’s delay dangerous. The decision to sail was understandable, but it was fatal: the torpedoes that hit her would have been survivable in a finished ship, with her watertight doors fitted and her damage-control parties trained, but in an unfinished ship they were fatal. The Shinano’s story is therefore a cautionary tale for every navy: that a ship is not ready for sea until she is finished, and that the pressure to sail before a ship is ready can kill more men than the enemy. The Japanese Navy learned the lesson too late, and the Shinano’s crew paid for it with their lives.

10. Surviving Examples

No Ship Survives

No part of the Shinano survives above water. The ship lies on the seabed of the Pacific Ocean, south of Japan, at a depth of about 4,000 metres, where she has lain since 29 November 1944. Her wreck has never been located with certainty, although several expeditions have searched for it, and it is unlikely ever to be raised or explored, because of its depth and because of its condition. The Shinano’s story is therefore preserved not in a museum but in documents, in photographs and in the memories of the survivors. The Yokosuka Naval Arsenal, where she was built, no longer exists as a naval shipyard, and the Kure Naval Arsenal, where she was to have been completed, is now a civilian shipyard. The Shinano’s only memorial is the record of her sinking, and the names of the men who died with her. The Shinano’s wreck, if it is ever found, will be a war grave, and the Japanese government has asked that it be left undisturbed, as a memorial to the men who died in her.

Models, Photographs and Memory

The Shinano is remembered in Japan through models, through photographs and through the accounts of the survivors. Scale models of the Shinano are popular in Japan, and the ship is a familiar subject for modellers, because of her size and because of her unusual history. Photographs of the Shinano are rare, because she was in service for only ten days and because the Japanese Navy kept her existence secret, but the photographs that do exist — of her launching at Yokosuka on 8 October 1944, and of her fitting-out in the harbour — are among the most famous photographs of Japanese warships. The survivors of the sinking, about 1,080 men, told their stories after the war, and their accounts are the principal source for the history of the ship’s last hours. The Shinano’s story is also told in the museum at Kure, the Yamato Museum, where a model of the ship is displayed alongside the great model of the Yamato herself, and where visitors can learn about the largest warships ever built and about the fate that befell them all.

Frequently Asked Questions

What was the Shinano?
The Shinano was a Japanese aircraft carrier of the Second World War, converted from the hull of a Yamato-class battleship. She was the largest aircraft carrier of the war, at about 65,000 tonnes standard displacement.

How long was the Shinano in service?
Ten days. She was commissioned on 19 November 1944 and sunk on 29 November 1944, on her first voyage from Yokosuka to Kure.

What sank the Shinano?
The American submarine USS Archerfish, commanded by Commander Joseph F. Enright, which fired six torpedoes at the Shinano on 29 November 1944, of which four hit.

How many men died when the Shinano sank?
About 1,435 of the about 2,515 men aboard died, including Captain Toshio Abe, who went down with his ship. About 1,080 survivors were rescued by the escorting destroyers.

Why did the Shinano sink so quickly?
She did not sink quickly — she took about seven hours to sink — but she sank because she was unfinished: her watertight doors were not fitted, her pumps were not installed, and her crew had not been trained in damage control, so the flooding from the torpedo hits could not be stopped.

Where is the wreck of the Shinano?
On the seabed of the Pacific Ocean, south of Japan, at a depth of about 4,000 metres. The wreck has never been located with certainty.

Sources

1. Wikipedia, “Japanese aircraft carrier Shinano” — displacement, commissioning and sinking dates, the Archerfish attack.
2. Hans Lengerer, The Aircraft Carrier Shinano (Seaforth Publishing, 2015) — the conversion, the design and the sinking.
3. U.S. Naval History and Heritage Command, “USS Archerfish (SS-311)” — the attack of 29 November 1944 and Enright’s report.
4. Mark Stille, Imperial Japanese Navy Aircraft Carriers 1921–45 (Osprey Publishing, 2005) — the Shinano as a support carrier.
5. Yamato Museum, Kure, “Shinano” — the ship’s history and the model on display at Kure.
6. Anthony P. Tully, “Shinano” (combinedfleet.com) — the sinking, the casualties and the survivors.