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H-044-3: “Operation Heaven Number One” (Ten-ichi-go)—the Death of Yamato, 7 April 1945


Photo #: NH 73092  Yamato

The Imperial Japanese Navy's super-battleship Yamato, shown here during pre-commission running trials in the Bungo Strait between the Home Islands of Kyushu and Shikoku, 20 October 1941 (NH 73092). 

H-Gram 044, Attachment 3

Samuel J. Cox, Director NHHC

April 2020

Senior U.S. Navy commanders in the Pacific, including Admiral Raymond Spruance, Commander U.S. Fifth Fleet, knew what the battleship Yamato’s mission was before almost anyone on Yamato did. The execute order for Operation Ten-ichi-go (“Heaven Number One”) was intercepted on 26 March 1945 and decrypted. Over the next days, additional messages were intercepted and decrypted by Fleet Radio Unit Pacific (FRUPAC) and also OP-20-G in Washington that provided increasingly detailed information on the operation’s timing and made specific mention of Yamato on 5 April.

Operation Ten-ichi-go was the Imperial Japanese Navy’s plan to react to the U.S. invasion of the island of Okinawa, which Japanese intelligence correctly determined would occur at the end of March 1945. (The actual U.S. landings on Okinawa commenced 1 April 1945, but carrier strikes and shore bombardment began a week earlier and the landings on the small islands of the Kerama-shōtto group just southwest of Okinawa occurred on 27 March.)

Yamato was essentially doomed by a question from Emperor Hirohito during a briefing on 29 March about plans for Japanese air opposition to expected landings on Okinawa. He asked what the Japanese navy was doing. This was taken by senior Japanese navy leaders as implicit criticism of their service’s inaction. By this time, there wasn’t much left of the Japanese navy that was still operational, and fuel was in critically short supply. The debate up to that point was whether to keep the fleet in home waters as a last-ditch defense or to send it on what everyone knew would be a one-way mission to attack the overwhelming U.S. forces expected to be at Okinawa. The emperor’s question clinched it. The commander in chief of the Combined Fleet, Admiral Soemu Toyoda, resolved to send what was left of his force out in a blaze of glory.

The mission was given to Vice Admiral Seiichi Ito, commander of the Japanese Second Fleet (pretty much all that was left of the Combined Fleet), embarked on the super-battleship Yamato. On 29 March, Yamato was ordered to take on fuel and ammunition, and loaded 1,170 shells for her nine 18.1-inch guns (in three triple turrets), 1,629 shells for her six 6.1-inch guns (in two triple turrets), 13,500 anti-aircraft shells, and 11.5 million rounds of machine-gun ammunition. It would not be enough.

Vice Admiral Ito initially objected to the mission, viewing it as futile and wasteful. According to the plan, Yamato, light cruiser Yahagi, and eight destroyers would form a “Surface Special Attack Force” (the term “special attack” was understood to mean suicide) and sortie on 6 April 1945. This would be carried out in conjunction with a mass aerial kamikaze attack by over 350 airplanes (Kikusui No. 1). The force would transit to Okinawa on 7 April (with only a few hours of minimal air cover), to arrive in daylight hours in the U.S. transport area off southwestern Okinawa on 8 April. The ships were to sink as many troop transports as possible, then beach themselves and continue firing as long as they had ammunition. At that point, the crews would go ashore to fight and die to the last man along with their army comrades.

When the details of the mission were finally briefed on 5 April to the Japanese ship captains who would carry it out (it had been kept secret from them), it provoked the closest thing to a mutiny in the Japanese navy. The chief of staff of the Combined Fleet, Vice Admiral Ryunosuke Kusaka, flew in from Tokyo to ensure that Ito would comply with Admiral Toyoda’s orders. The ship captains were then assembled on Yahagi and briefed. They unanimously objected, most of them arguing instead to be allowed to conduct independent raiding of the over-extended U.S. supply lines. As later described by the captain of Yahagi, Captain Tameichi Hara, the meeting was quite contentious. None of the captains was afraid to die—they just objected to the sheer folly of attacking in daylight without air cover, believing that they wouldn’t get anywhere close to Okinawa. (They were right.) They eventually fell in line when informed that this was what the emperor wanted, that the force would serve to support the mass kamikaze air attack, and that it was an order. They were also given the option of not participating, an option none of them took.

Yamato and her sister ship Musashi, sunk during the Battle of Leyte Gulf, were, at 65,000 tons displacement (72,000 tons fully loaded), the largest battleships ever built. Even before the war, the Japanese understood that they could never match the U.S. Navy for quantity, but were convinced they could build a better battleship. Design commenced in 1934, construction began in 1937 (in great secrecy) and Yamato was commissioned in December 1941 just after Pearl Harbor. Her main armament consisted of three triple 18.1-inch gun turrets that could hurl a 3,200-pound shell (compared to 2,700 pounds for the U.S. 16-inch shells) to a range of just over 22 miles. Her waterline armor belt was 16 inches thick. Her secondary armament was significantly altered during the war by removing two of her four triple 6.1-inch turrets in favor of increased anti-aircraft armament, which, by 1945, included 12 dual 5-inch gun mounts, 54 25-mm triple mounts (162 guns), and smaller machine guns. Yamato had been fitted with multiple air and surface search radars, as well as radio-intercept capability. She had suffered minor damage in the bridge area from a bomb hit by a Helldiver dive-bomber off Intrepid (CV-11) during U.S. carrier strikes on Kure and the Inland Sea on 19 March, but was fully fit for battle.

Yamato was commanded by Captain Kosaku Aruga (spelled Ariga in some accounts). Also, accounts differ as to whether he was a captain or rear admiral. To buck up morale, many captains of capital ships received a “accelerated” promotion to rear admiral in 1944. Thus, it’s possible Aruga was “selected,” but not yet “promoted.” In keeping with Japanese practice of posthumous promotion for death in battle, he was promoted to vice admiral after Yamato was sunk, that much is fact.

The rest of the Surface Special Attack Force consisted of the light cruiser Yahagi, and eight destroyers. Yahagi was a relatively small light cruiser (6,600 tons) completed in 1943 and intended for use as a destroyer flotilla leader. With only three twin 6-inch gun turrets, she was no match for U.S. light cruisers with their four triple-turret, rapid-fire 6-inch guns. Yahagi was commanded by Captain Tameichi Hara (the only Japanese destroyer skipper at the start of the war who was still alive at the end of the war), with Rear Admiral Keizo Komura, commander of Destroyer Squadron 2, embarked. The destroyers were Destroyer Division (DESDIV) 17 (Isokaze, Hamakaze, Yukikaze), DESDIV 21 (Asashimo, Kasumi, Hatsushimo), and DESDIV 41 (Fuyuzuki, Suzutsuki). The destroyers were an assortment of different classes (what was left in operation, since the Japanese would lose 120 destroyers during the war), but all were armed with powerful Type 93 “Long Lance” 24-inch torpedoes.

Before getting underway, the Surface Special Attack Force put ashore 67 recently arrived midshipmen of the Etajima Naval Academy Class No. 74, although many begged to stay. In addition, sick sailors and also the oldest sailors were sent to shore. The morale aboard Yamato was described as not being very good, especially after the crews were informed they were on a one-way mission. (Although some accounts say that, according to the plan, the ships were only given enough fuel to reach Okinawa, they actually received as much fuel as was available to give.)

U.S. submarines were already waiting for Yamato, with orders to report rather than attack, although with the force transiting at 22 knots and frequently zig-zagging, successful attack in all but the luckiest circumstances was unlikely. As Yamato and escorts were transiting the Bungo Strait between the Home Islands of Kyushu and Shikoku on 6 April 1945, submarine Threadfin (SS-410) sighted the force at about 1745 and issued a contact report in the clear that was intercepted by Yamato. At 1830, destroyer Isokaze sighted Threadfin on the surface. At 2144, the submarine issued a detailed contact report with an accurate force disposition. Submarine Hackleback (SS-295) then picked up surveillance, issuing four contact reports during the night as Yamato transited southwesterly along the coast of Kyushu. A Japanese destroyer peeled off three times to keep Hackleback at bay. However, in order to keep up with Yamato, these forays were short-lived. The submarine radio traffic transmitted in the clear, reporting Yamato by name, and reported by Japanese radio intelligence, did nothing to improve the sense of foreboding felt by the senior officers on Yamato. (The Yamato force had a Nisei radio-intelligence operator. Although born a U.S. citizen, he had been studying in Japan when the war broke out and had the choice of execution or serving in the Imperial Japanese Navy.)


Yamato maneuvers frantically under attack as a bomb explodes off its port side. The fire in the area of the 6.1 inch turret can be clearly seen.

Just after 1240 on 7 April, Yamato maneuvers frantically under the initial attack by USS Bennington (CV-20)and USS Hornet (CV-12) aircraft as a bomb explodes off her port side. The fire in the area of her forward 6.1 inch turret can be clearly seen (L42-09.06.05).                         

Both the U.S. Fifth Fleet commander, Admiral Spruance, and Vice Admiral Mitscher (commander of the Fast Carrier Task Force, TF 58), who had access to the Ultra communications intelligence and were expecting the sortie, immediately reacted to the submarine reports. Mitscher ordered all four of his carrier task groups to proceed as soon as possible to launch positions northeast of Okinawa with the intent to destroy Yamato before it got anywhere near Okinawa. TG 58.1 and 58.3 were quickly on station. TG 58.4 had just finished refueling and would arrive just in time. TG 58.2 was in the act of refueling and wouldn’t get there in time. Spruance gave orders to Rear Admiral Morton Deyo, commander of the Bombardment Force, to take his six old battleships and set up a blocking force northwest of Okinawa (as Yamato was circling around in that direction with the intent to stay as far from TF 58 as possible). During the night, this plan morphed into sending six new battleships detached from TF 58 into blocking position. This force include battleships Massachusetts (BB-59), Indiana (BB-58), South Dakota (BB-57), New Jersey (BB-62), Wisconsin (BB-64), and Missouri (BB-63) (54 16-inch guns), the battle-cruisers Alaska (CB-1) and Guam (CB-2), five cruisers, and 21 destroyers. They would not be needed.

After daybreak on 7 April 1945, a paltry six A6M Zeke fighters showed up to provide combat air patrol over Yamato. Between then and 1000, a total of 14 Zekes would provide cover. FRUPAC had the message that the air cover would end at 1000, which was also known to senior U.S. Navy commanders.

At 0657, destroyer Asashimo, with Captain Kotaki, DESDIV 21, embarked, sent a signal that she was having engine trouble and began to fall behind. This was taken as a yet another bad omen.

At 0823, a Hellcat fighter off Essex (CV-9) sighted Yamato, a contact that the battleship reported at 0832. The visibility was highly variable, but often not very good due to cloud cover. The fighter issued a contact report at 0832. At 0840, the Japanese reported seven Hellcats orbiting around the force. The Japanese fighters were unable to make contact before they left at 1000. With this contact information, Spruance ordered Deyo to ready the blocking force. Since Yamato could not get to the landing area before 8 April, there wasn’t a big rush and Deyo convened a planning conference on his flagship Eldorado (AGC-11) at 1030 with plans to sortie TF 54 from the bombardment area at 1530. Aboard the TF 58 carriers, the strike packages were remaining ready on deck while the searches were underway.

Not long after the Hellcat sighting, two PBM-3 Martin Mariner flying boats began shadowing Yamato, maintaining discreet contact for the next five hours while mostly hidden in the clouds. The Mariners were subordinate to Patrol Bombing Squadron 21 (VPB-21), operating from the tender Chandeleur (AV-10), which had arrived at Kerama Retto on 28 March.

At 1000, Task Group 58.1 and Task Group 58.3 commence launching a 280-plane strike wave (132 fighters, 50 bombers, and 98 torpedo planes). TG 58.1, commanded by Rear Admiral J. J. “Jocko” Clark, embarked on Hornet (CV-12), included Hancock (CV-19), Bennington (CV-20), Belleau Wood (CVL-24) and San Jacinto (CVL-30). TG 58.3, commanded by Rear Admiral Frederick “Ted” Sherman, embarked on Essex (CV-9), included Bunker Hill (CV-17), Bataan (CVL-24), and Cabot (CVL-28). Mitscher, CTF 58, was embarked on Bunker Hill. Hancock for some reason launched her 53-plane strike late, and it  never found Yamato in the murk, reducing the overall first strike to 227 aircraft.

At 1014, the Yamato force sighted the two Martin Mariner PBM flying boats, and also noted that Hackleback was still trailing (the Japanese had made so many course changes during the night that the sub was able to “cut the corner” and maintain contact on the force). At 1017, Yahagi commenced jamming the Mariner’s communications, but by then it was too late. At 1017, Yamato opened fire with several of her special main-battery anti-aircraft shells (sanshikidan or “beehive” shells, somewhat like a giant shotgun shell), at the Mariners, which was equally futile, although the Mariners ducked back in the clouds.

At 1107, Yamato’s Type 13 air search radar detected a large aircraft formation inbound at the radar’s maximum range of 63 nautical miles, and noted the aircraft formation was splitting into two groups. The Yamato group cranked up speed to 25 knots.

At 1115, Yamato’s radar indicated the two air groups were at 44 miles and closing rapidly. The battleship received a 30-minute time-late report from an observation post on a small Japanese island north of Okinawa that 150 U.S. planes were headed in Yamato’s direction. The Japanese also noted eight Hellcats circling the force with impunity because of no Japanese fighter cover, and remaining outside anti-aircraft range.

At 1210, destroyer Asashimo, lagging behind the force, reported that she was under air attack, and radio transmissions from her ceased. Asashimo was first attacked by aircraft from Bunker Hill and then, a few minutes later, by aircraft from San Jacinto, which scored killing hits with torpedoes and bombs. Asashimo went down with all 330 hands. (Based on erroneous San Jacinto report, Samuel Eliot Morison misidentifies this ship as Hamakaze, but a photo shows a Yugumo-class destroyer, which would be Asashimo, and which was also the one lagging behind.)


Photo #: NH 62581  "Ten-Go" Operation, April 1945

Yamato maneuvers while under attack by U.S. Navy carrier planes north of Okinawa, 7 April 1945, maneuvering evasively at a brisk 15 to 20 knots. One fire can be observed amidships from the initial strike, but no list has developed at this point. Photographed from a USS Yorktown (CV-10) plane (NH 62581).

At 1232, lookouts in the Yamato force sighted the first incoming strike wave. Captain Hara on Yahagi reported that the large formations of aircraft circled around the task force just outside anti-aircraft range for a number of minutes, some in clockwise rotation and some in counter-clockwise rotation, as strike leaders organized strikes on particular targets free of interference from Japanese fighters. At 1234, Yamato opened fire with her two forward main battery turrets, lobbing sanshikidan shells at the U.S. aircraft—to no effect.

At about 1237, U.S. aircraft commenced attack runs, with strafing and rockets from fighters (which quickly began decimating Japanese anti-aircraft gunners), and then bombs and torpedoes. The Japanese opened up with everything they had, which looked terrifying, but U.S. pilots quickly figured out that Japanese anti-aircraft fire was wildly inaccurate. Far more effective was the extraordinary skill of Japanese ship captains in making evasive maneuvers to throw off aim and avoid numerous bombs and torpedoes. Numerous Helldivers from Bennington and Hornet attacked from Yamato’s port side and numerous near misses splashed all around the battleship, which was moving at flank speed (27 knots), before she was finally hit by two 1,000-pound armor-piercing bombs at 1240. One bomb exploded in crews’ quarters, but the other bomb exploded near the aft command station and knocked out one of her two air search radars, the aft secondary gun director, several 25-mm gun mounts, and started a fire that killed all but one crewman in the after secondary (6-inch) gun turret and that couldn’t be put out. One Helldiver was shot down.

At 1243, five Hornet Avengers came in from port, while 14 F4U Corsairs from Bunker Hill were strafing and hitting Yamato with rockets that caused little damage to the ship, but were deadly to the gunners. One Avenger was shot down, but three torpedoes went into the water. Yamato avoided two, but the third hit her port side at 1245. She quickly shipped 2,235 tons of water, but the list was soon corrected with effective counter-flooding. U.S. aircrew claimed additional bomb and torpedo hits in this first wave, but these were mostly near misses.

Light cruiser Yahagi steered away from Yamato in an attempt to draw attention away from the battleship—too successfully. At 1246, she took a direct torpedo hit in the engine room that killed the entire engine room crew and left her dead in the water, unable to avoid further hits. The destroyer Isokaze rushed to aid Yahagi and take off Rear Admiral Komura, but got pummeled by bombs before she got close. Meanwhile, about 34 Hellcats and Corsairs and 22 Helldivers and Avengers worked over some of the other Japanese destroyers. A near miss on Hamakaze disabled her starboard shaft and then, at 1247, torpedo hits amidships blew her in half. A 500-pound general-purpose bomb hit Suzutsuki and blew off her bow. Fuyutsuki was hit by two dud rockets. The first U.S. attack wave ended about 1250.

At 1302, Yamato’s remaining air search radar detected a second inbound wave. These were 50 aircraft from Essex and Bataan. At 1322, an Essex Corsair hit Yamato in the port bow with a 1,000-pound general-purpose bomb. (Although U.S. carrier air groups’ complement had been changed to have a mix of about three quarters fighters to defend against kamikaze and only one quarter bombers and torpedo planes, the fighters had been trained and gotten pretty good at being used in a fighter-bomber role, and, with no Japanese air opposition, had the freedom to do so.) Twelve Helldivers claimed several hits in the bridge area in exchange for five Helldivers damaged by anti-aircraft fire. By this point, Yamato was firing main-battery beehive shells set to detonate after one second (about 3,000 yards) from the ship, which U.S. aircraft just blew through.

At 1333, another 110 aircraft from TG 58.4 (Yorktown, Intrepid, and Langley), which had launched after the first wave of 280 aircraft, commenced their attack on Yamato. This time, all attacks concentrated on the battleship. Twenty Avengers attacked from the port side (concentrating torpedo attacks from the port side was deliberate, with the intent to capsize the ship). Three of the torpedoes hit in quick succession, and Yamato took on another 3,000 tons of water and a 7-degree list. Having already counter-flooded to starboard, the only option Yamato had was to flood her starboard engine and boiler rooms. The desperate measure worked, but, with insufficient time to give warning, several hundred Yamato crewmen were drowned as a result, and the ship was slowed to 10 knots, which made her an easier target.

At 1342, another Avenger was shot down, but four more torpedoes were inbound from the port side and two hit. With Yamato slowed, U.S. torpedo planes started to deliberately target her stern to knock out her steering, and she became stuck in a starboard turn. Yamato took at least four more bomb hits in the superstructure area, which wiped out many of the remaining 25-mm guns. A bomb impact in the dispensary killed many of the wounded who had been gathered there, along with many of the medical personnel.

The executive officer reported to Captain Aruga that the damage control officers were dead and that counter-flooding could no longer correct the list, and recommended the ship be abandoned. Since Yamato’s radios were destroyed, Vice Admiral Ito sent out a signal via flag hoist cancelling the operation and freeing the other ships to try to get back to Japan.


Photo #: 80-G-413914  "Ten-Go" Operation, April 1945

At 1430 on 7 April 1945, more than 300 nautical miles north of Okinawa, Yamato blows up after capsizing. Three Japanese destroyers are nearby (80-G-413914). 

At 1402, Yamato took three more bomb hits amidships, and Aruga gave the abandon-ship order. At 1407, she was struck by at least the seventh torpedo, this time to starboard. At 1417, she took an eighth and ninth torpedo, both to port. By this point, the uncorrected list was passing 15 degrees to port, and alarms were warning of critical temperatures in the forward main battery magazines, with no working pumps to flood them.

As Yamato continued to list to port, her starboard armor belt came out of the water and her vulnerable underside became exposed. Six Yorktown Avengers attacked from the starboard side, with their Mark 13 torpedoes re-set for a 20-foot depth—several hit.

 Meanwhile, the dead-in-the-water Yahagi had soaked up at least 12 bombs and seven torpedo hits before she finally capsized and sank at 1405.

By 1408, Yamato had clearly begun to capsize and the ship was being abandoned. Vice Admiral Ito retired to his stateroom to go down with the ship. Captain Aruga lashed himself to the binnacle to do the same. By 1420, the main deck was vertical and, at 1430, Yamato had rolled over and just gone under when the No.1 forward magazine detonated in a massive explosion that killed almost all of Yamato’s crew who had survived to that point and raised a pall of smoke that could be seen for 100 miles. More U.S. aircraft may have been knocked down by the magazine explosion than by Japanese anti-aircraft fire.

Although accounts vary about how many crewmen were on Yamato, the most definitive appears to be that 3,055 of 3,332 crewmen were lost. According to Morison, there were only 23 officers and 246 enlisted sailors who survived, which doesn’t exactly match, but is close. Vice Admiral Ito and Captain Aruga went down with the ship. Aruga would be posthumously promoted to vice admiral and Ito to full admiral. Ito’s chief of staff, Rear Admiral Nobuei Morishita, was the senior survivor of Yamato.

Yahagi lost 446 of about 1,000 crewmen. Both Rear Admiral Komura and Captain Hara survived. Of the Japanese destroyers, Asashimo was sunk with all hands (about 330) and Hamakaze sank with a loss of 100 crewmen and 45 wounded (257 were rescued). Isokaze, which had her steering disabled by a near miss, suffered 20 dead and 54 wounded, and had to be scuttled by gunfire from Yukikaze. Kasumi, which had her steering disabled by two bomb hits, suffered 17 dead and 47 wounded, and was scuttled by two torpedoes from Fuyuzuki. Suzutsuki suffered 57 dead and 34 wounded, but, despite having her bow blown off, made it back to Sasebo, Japan, steaming in reverse the whole way; she was never repaired. Fuyuzuki suffered light damage from dud rockets, suffered 12 dead and 12 injured, and was repaired, but had her stern blown off by a mine after the August cease-fire. Yukikaze suffered three dead from strafing and survived the war. Hatsushimo suffered only three wounded on 6 April, but, on 20 July, struck a mine and was the last Japanese destroyer sunk in the war.

Japanese reports claim U.S. aircraft strafed survivors in the water, but also report that attacks ceased on destroyers that were picking up survivors. About 1,620 survivors of Yamato, Yahagi, Hamakaze, Isokaze, and Kasumi were rescued by the surviving Japanese destroyers. A U.S. PBM Mariner also rescued several Japanese survivors. About 1,187 crewmen of Yahagi and the four destroyers were lost. Combined with Yamato, about 4,242 Japanese sailors gave their lives for the emperor on 7 April. Yamato was still more than 300 nautical miles from Okinawa when she went down. The most powerful battleship in the world was no match for 390 U.S. carrier aircraft.

U.S. losses were 10 aircraft and 12 pilots and aircrewmen.

Captain Hara of Yahagi later said the mission would be “like throwing an egg against a rock.”

Sources include: NHHC Dictionary of American Fighting Ships (DANFS) for U.S. ships and combinedfleet.com for Japanese ships. History of United States Naval Operations in World War II, Vol. XIV: Victory in the Pacific by Samuel Eliot Morison, Boston: Little Brown and Co., 1969; Japanese Destroyer Captain by Tameichi Hara, New York: Ballantine Books, 1961; Combined Fleet Decoded: The Secret History of American Intelligence and the Japanese Navy in World War II by John Prados, New York: Random House, 1995.

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Published: Fri Apr 03 15:24:09 EDT 2020