Japanese Aircraft Carrier Shinano - Commissioning and Sinking

Commissioning and Sinking

On 19 November 1944, Shinano was formally commissioned at Yokosuka, having spent the previous two weeks fitting out and performing minor trials. By 1 October the crew had reported on board, 70 to 75 percent of which had no previous sea duty experience. As a result of growing worry for her safety, due to a U.S. bomber fly-over, Japanese Naval Command ordered Shinano to Kure, where the remainder of her fitting-out would take place. Naval Command wanted Shinano moved to Kure no later than 28 November. However, Abe asked for a delay in the sailing date. The majority of her watertight compartment doors had yet to be installed, the compartment air tests had not been conducted, and many holes for electrical cables, ventilation ducts and pipes had not been sealed. Nor had the fire mains or drainage systems been completed as pumps had not been delivered. He also wanted more time to train his new crew, and to give the crews of the destroyers a rest after returning from battle.

Abe's request was denied, and Shinano departed as scheduled at 18:00 on 28 November escorted by the destroyers Isokaze, Yukikaze and Hamakaze. Abe commanded a crew of 2,176 officers and men. Also on board were 300 shipyard workers and 40 civilian employees. Watertight doors and hatches were left open for ease of access to machinery spaces, as were some manholes in the double and triple bottomed hull. Abe would have preferred a daytime passage, but was unable to get Naval Command to provide air support; all available planes were needed for combat duty. She also carried six Shinyo suicide boats, and 50 Ohka suicide rockets. Her orders were to go to Kure, where she would complete her fitting-out and commence to the Inland Sea after which Shinano was to take the Ohka east for "the relief of the Philippines". Abe was due to be promoted to rear admiral once Shinano completed her fitting-out, and take command of a fleet of attack carriers being built up in the east. Although Shinano was to act as a support carrier, she was also assigned her own air group, commanded by Lieutenant Commander Yoshio Shiga, a veteran of the attack on Pearl Harbor. Shiga's air group would have already been aboard when Shinano sortied for Kure, but four of the carrier's 12 boilers were not in service due to lack of parts. This cut her top speed from 27 kn (50 km/h; 31 mph) to 21 kn (39 km/h; 24 mph) — too slow for planes to launch without a headwind.

At 21:00, the American submarine USS Archer-Fish—commanded by Commander Joseph F. Enright—picked up Shinanos task group on her radar. Normally, Shinano would have been able to outrun Archer-Fish. However, the submarine was able to remain in pursuit of Shinano because the zig-zagging pattern of Shinano and her escorts—intended to avoid submarine attack—inadvertently turned the task group back into the sub's path on several occasions. Abe's zig-zagging was guided by his assumption that Archer-Fish was part of an American "wolfpack". He believed that Archer-Fish was being used as a decoy to lure away one of the escorting destroyers, allowing the rest of the pack a clear shot at Shinano. He actually ordered one of the destroyers to turn back when he spotted it trying to ram Archer-Fish, in part because he believed it left Shinano's bow exposed to an ambush. Additionally, Shinano was slowed because it was only running on four of her six operational boilers on two propeller shafts. Shinano was slowed further mid-pursuit after a bearing overheated one of the shafts, forcing a reduction in the propeller turns to reduce the operating RPMs of that engine. As a result, Shinano was forced to reduce its top speed to the same speed as most American subs.

On 29 November Abe was still worrying about the submarine spotted 48 hours earlier, and all three following destroyers kept changing course erratically. Once again the zig-zagging put Shinano into the path of Archer-Fish. At 3:05 am, Archer-Fish dove. Enright quickly moved Archer-Fish in front of the carrier group. However, just as Enright was about to loose his torpedoes, one of the destroyers on Shinano's starboard beam broke away and set course straight for Archer-Fish. Expecting depth charges, Enright ordered a descent to 62 feet, but the destroyer passed overhead seemingly unaware of them, after which Archer-Fish rose back to 60 feet. At 3:15 am, Archer-Fish fired six shallow-running torpedoes in sequence before diving to 400 feet to escape a depth charge attack from the escorts. Enright later said he set the torpedoes to run shallow in hopes of capsizing it.

Four of the six torpedoes found their mark. The first torpedo struck Shinano towards the stern, ripping through the hull into refrigerated areas and one of the empty aviation gasoline-storage tanks. The explosion also killed the sleeping engineering personnel in the compartments above. The second torpedo struck some 8 seconds after the first and 50 yards ahead into the starboard outboard propeller shaft, flooding the outboard engine-room. The third torpedo took out the No. 3 fireroom, killing every man on watch. The fourth and final torpedo detonated against the starboard air compressor room, flooding it and neighboring magazines while also rupturing the starboard oil-tank.

Abe quickly ordered a damage report and sounded battle stations. He initially thought Shinano had enough armor to withstand the damage, since American torpedoes had smaller warheads and fewer explosives than their Japanese counterparts. With this in mind, he ordered the navigator to maintain full speed. However, within minutes Shinano had already listed roughly 10 degrees to starboard. Archer-Fish's crew later reported seeing Shinano listing only minutes after the last torpedo hit. The executive officer later reported that only minutes after the last torpedo hit, he heard air rushing through gaps in the watertight doors which had been left untested before departure—a sign that seawater was rapidly entering the ship, proving the doors unfit. Though severe, the damage to Shinano was at first judged to be manageable, and the carrier continued under way. The crew were confident in Shinano´s armor and its strength, which translated into lax efforts to save the ship initially. Captain Abe ordered a change of course towards Shiono Point and for the ship to be righted by counter-flooding, which reduced the list to 7 degrees.

At dawn Shinano was still making 18 knots with the remaining boilers and machinery when the starboard boiler-room flooded completely and increased the list to 20 degrees, at which point the port trimming tanks valves rose above the waterline and became ineffective. Speed dropped to 10 knots and the port boiler rooms were ordered flooded in desperation, stemming the list momentarily before it continued. All efforts to control the flooding failed, in part because most of the crew was not well trained in damage control. No flooding boundaries were set up either, which would be the norm, and few portable pumps were available or properly used by the inexperienced crew.

At 06:00, Shinano's boiler feed water was exhausted. At 7:45 am, she lost all power, and ceased all forward motion shortly afterward. Panic increasingly spread among the crew, who were also confused by the mix of civilian personnel in similar uniform who were "disobeying" orders given to them. At 08:50, Captain Abe messaged the destroyers Hamakaze and Isokaze to take her in tow, to attempt beaching her on Cape Ushio. However, the two escorts only displaced 5,000 long tons (5,100 t) between them, not nearly enough to overcome the list. The first cables snapped under the strain from pulling the waterlogged ship, and the second attempt was aborted for fear of injury to the men.

At 10:18, Abe gave the order to abandon ship; by this time Shinano was listing 30 degrees to starboard. As she heeled her flightdeck touched the water, which flowed into the open deck elevator; sucking mobs of sailors back into the ship as she sank. At 10:57 Shinano finally capsized and sank 200 km (110 nmi; 120 mi) southeast of Shingū (32°0′N 137°0′E / 32°N 137°E / 32; 137), her stern slipping under first with the bow pointing skyward. She took 1,435 men and officers to their deaths, including Abe and both of his navigators. Rescued were 55 officers, 993 petty officers and men, plus 32 civilians for a total of 1,080 survivors. The survivors of Shinano's sinking were quarantined in Japan for several months following her sinking.