Today, I'm going to tell you about one of the most significant engagements of World War II. Unless you are a Submariner, it's likely that you've never heard about this story - when the USS Archerfish, commanded by Joseph F. Enright, sand the Japanese Aircraft Carrier Shinano.

The Shinano was originally planned to be a Yamato-class battleship, but the partially complete hull was ordered to be converted to an aircraft carrier following Japan's disastrous loss of four of her original six fleet carriers at the Battle of Midway in mid-1942.

The ship was originally scheduled for completion in April 1945, but construction was expedited after the defeat at the Battle of the Philippine Sea in June 1944 as the IJN anticipated that the US could now bomb Japan with long-range aircraft from bases in the Mariana Islands.

Shinano departed as scheduled with the escorting destroyers at 18:00 on 28 November. Abe commanded a crew of 2,175 officers and men. Also on board were 300 shipyard workers and 40 civilian employees.

Captain Toshio Abe preferred a daylight passage, since it would have allowed him extra time to train his crew and given the destroyer crews time to rest. However, he was forced to make a nighttime run when he learned the Navy General Staff could not provide air support.

Her orders were to go to Kure, where she would complete fitting out and then deliver the kamikaze craft to the Philippines and Okinawa. Traveling at an average speed of 20 knots, she needed sixteen hours to cover the 300 miles to Kure.

As a measure of how important Shinano was to the naval command, Abe was slated for promotion to rear admiral once its fitting out was complete.

Enter Commander Enright and the dedicated crew of the Archerfish.

At 20:48, the Archerfish picked up Shinano and her escorts on her radar and pursued them on a parallel course. Over an hour and a half earlier, Shinano had detected the submarine's radar.

Normally, Shinano would have been able to outrun Archerfish, but the zig-zagging movement of the carrier and her escorts—intended to evade any American subs in the area—inadvertently turned the task group back into the sub's path on several occasions.

At 22:45, the carrier's lookouts spotted Archerfish on the surface and the Destroyer Isokaze broke formation, against orders, to investigate. Abe ordered the escort to return to the formation without attacking because he believed the submarine was part of an American wolfpack.

American wolfpacks, officially called coordinated attack groups, usually comprised three boats that patrolled in close company and organized before they left port under the command of the senior captain of the three.

Abe assumed Archerfish was being used as a decoy to lure away one of the escorts to allow the rest of the pack a clear shot at Shinano. He ordered his ships to turn away from the submarine with the expectation of outrunning it, counting on a 2-kt margin of speed over the sub.

Around 23:22, the carrier was forced to reduce speed to 18 knots, the same speed as Archerfish, to prevent damage to the propeller shaft when a bearing overheated.

At 02:56 on 29 November, Shinano turned to the southwest and headed straight for Archerfish. Eight minutes later, Archerfish turned east and submerged in preparation to attack.

Enright ordered his torpedoes set for a depth of 10 feet in case they ran deeper than set; he also intended to increase the chances of capsizing the ship by punching holes higher up in the hull.

A few minutes later, Shinano turned south, exposing her entire side to Archerfish, a nearly ideal firing situation for a submarine. The escorting destroyer on that side passed right over Archerfish without detecting her.

At 03:15 Archerfish fired six torpedoes (every available weapon) before diving to 400 feet (120 m) to escape a depth charge attack from the escorts.

Four torpedoes struck Shinano, at an average depth of 14. The first hit towards the stern, flooding refrigerated storage compartments and one of the empty aviation gasoline storage tanks, and killing many of the sleeping engineering personnel in the compartments above.

The second hit the compartment where the starboard outboard propeller shaft entered the hull and flooded the outboard engine room.

The third hit further forward, flooding the No. 3 boiler room and killing every man on watch. Structural failures caused the two adjacent boiler rooms to flood as well.

The fourth flooded the starboard air compressor room, adjacent anti-aircraft gun magazines, and the No. 2 damage-control station, and ruptured the adjacent oil tank.

Though severe, the damage to Shinano was at first judged to be manageable. The crew were confident in the ship's armor and strength, which translated into lax initial efforts to save the ship. This overconfidence extended to Abe.

He doubted the sub's torpedoes could inflict serious damage, since he knew that American torpedoes were less potent than Japanese torpedoes. He ordered the carrier to maintain its maximum speed even after the last torpedo hit.

This was a huge mistake the speed pushed more water through the holes in the hull resulting in extensive flooding. Within a few minutes she was listing 10 degrees to starboard... Part 2 below.

At 06:00 her list had increased to 20 degrees after the starboard boiler room flooded, at which point the valves of the port trimming tanks rose above the waterline and became ineffective.

The engines shut down for lack of steam around 07:00, and Abe ordered all of the propulsion compartments evacuated an hour later.

Abe ordered Hamakaze and Isokaze to take her in tow. However, the two destroyers only displaced 5,000 metric tons (4,900 long tons) between them, about one-fourteenth of Shinano's displacement and not nearly enough to overcome her deadweight.

At 10:18, Abe gave the order to abandon ship; by this time Shinano had a list of 30 degrees. As she heeled, water flowed into the open elevator well on her flight deck, sucking many swimming sailors back into the ship as she sank.

At 10:57 Shinano finally capsized and sank stern-first at coordinates (33°07′N 137°04′E), 65 miles from the nearest land, in approximately 13,000 ft of water, taking 1,435 officers, men and civilians to their deaths.

The dead included Abe and both of his navigators, who chose to go down with the ship. Rescued were 55 officers and 993 petty officers and enlisted men, plus 32 civilians for a total of 1,080 survivors.

After their rescue, the survivors were isolated on the island of Mitsuko-jima until January 1945 to suppress the news of the carrier's loss. The carrier was formally struck from the Naval Register on 31 August.

This is where the story gets strange. Naval Intelligence didn't believe that the carrier even existed. Shinano's construction had not been detected through radio messages or other means, and the American analysts believed that they had located all of Japan's surviving carriers.

Enright was eventually credited with sinking a 28,000 ton Hayatake (Hiyō-class) carrier by the acting commander of the Pacific Fleet's submarine force on the basis of a drawing Enright submitted depicting the ship he had attacked.

Once the existence of Shinano was discovered, Enright was credited with her sinking and awarded the Navy Cross. With a full-load displacement of 72,000 tons, Shinano is the LARGEST WARSHIP IN HISTORY to be sunk by a submarine.

Credit to Wikipedia - https://en.wikipedia.org/wiki/Japanese_aircraft_carrier_Shinano

Enright eventually wrote a book about the encounter also.