Ten-gō sakusen (Kyūjitai: 天號作戰, Shinjitai: 天号作戦; "Operation Heaven One"), also known as Ten-ichi-go and Operation Ten-Go, was the last major Japanese naval operation in the Pacific Theater of World War II.
In April 1945, the Japanese battleship Yamato, the largest battleship in the world, along with nine other Japanese warships, embarked from Japan on a deliberate suicide attack upon Allied forces engaged in the Battle of Okinawa. The Japanese force was attacked, stopped, and almost completely destroyed by United States (U.S.) carrier-borne aircraft before reaching Okinawa. Yamato and five other Japanese warships were sunk.
The battle demonstrated U.S. air supremacy in the Pacific theater by this stage in the war and the vulnerability of surface ships without air cover to aerial attack. The battle also exhibited Japan's willingness to sacrifice large numbers of its people in desperate attempts (see kamikaze) to slow the Allied advance on the Japanese home islands.
With the invasions of Saipan and Iwo Jima, Allied forces began their campaign against the Japanese homeland. As the next step before a planned invasion of the Japanese mainland, Allied forces invaded Okinawa on April 1, 1945. In March, in briefing Emperor Hirohito on Japan's response to the expected Okinawan invasion, Japanese military leaders explained that the Japanese Imperial Army was planning extensive air attacks, including the use of kamikaze. The emperor then reportedly asked, "But what about the Navy? What are they doing to assist in defending Okinawa?" Now feeling pressured by the emperor to mount some kind of attack also, Japan's Navy commanders conceived a kamikaze-type mission for their remaining operational large ships, which included the battleship Yamato.
The resulting plan—drafted under the direction of the Commander in Chief of the Combined Fleet, Admiral Toyoda Soemu,—called for Yamato and her escorts to attack the U.S. fleet supporting the U.S. troops landing on the west of the island. Yamato and her escorts were to fight their way to Okinawa and then beach themselves between Higashi and Yomitan and fight as shore batteries until they were destroyed. Once destroyed, the ship's surviving crewmembers were supposed to abandon the ships and fight U.S. forces on land. Very little, if any, air cover could be provided for the ships, which would render them almost helpless to concentrated U.S. air attacks. In preparation for executing the plan, the assigned ships left Kure for Tokuyama, off Mitajiri, Japan, on March 29. However, despite obeying orders to prepare for the mission, Admiral Ito Seiichi, commander of the Ten-Go force, still refused to actually order his ships to carry it out, believing the plan to be futile and wasteful.
Vice Admiral Kusaka Ryunosuke flew from Tokyo on April 5 to Tokuyama in a final attempt to convince the assembled commanders of the Combined Fleet, including Admiral Ito, to accept the plan. Upon first hearing of the proposed operation (it had been kept secret from most of them), the Combined Fleet commanders and captains unanimously joined Admiral Ito in rejecting it for the same reasons that he had expressed. Admiral Kusaka then explained that the Navy's attack would help divert U.S. aircraft away from the Army's planned air attacks on the U.S. fleet at Okinawa. He also explained that Japan's national leadership, including the emperor, were expecting the Navy to make their best effort to support the defense of Okinawa. Upon hearing this, the Combined Fleet commanders relented and accepted the proposed plan. The ship's crews were briefed on the nature of the mission and given the opportunity to stay behind if desired—none did. However, new, sick, and infirm crew members were ordered off the ships. The ships' crews now engaged in some last-minute intense drills to prepare for the mission, mostly practicing damage-control procedures. At midnight the ships were fueled. Reportedly, in secret defiance of orders to provide the ships with only just enough fuel to reach Okinawa, the Tokuyama personnel actually gave Yamato and the other ships almost all of the remaining fuel in the port, although this probably still was not enough to allow the force to return to Japan from Okinawa.
At dawn on April 7, the Japanese force passed the Osumi Peninsula into the open ocean heading south from Kyūshū towards Okinawa. They shifted into a defensive formation, with Yahagi leading Yamato and the eight destroyers deployed in a ring around the two larger ships, with each ship 1,500 meters from each other and proceeding at 20 knots. One of the Japanese destroyers, Asashimo, developed engine trouble and turned back. U.S. reconnaissance aircraft began to shadow the main force of ships. At 10:00, the Japanese force turned west to make it look like they were withdrawing, but at 11:30, after being detected by two American PBY Catalina flying boats (against which Yamato fired a salvo with her 460 mm bow guns using special ), they turned back towards Okinawa.
Around 10:00 on April 7, the U.S. Navy began launching almost 400 aircraft in several waves from eleven carriers of Vice Admiral Marc A. Mitscher's Task Force 58 (Hornet, Bennington, Belleau Wood, San Jacinto, Essex, Bunker Hill, Hancock, Bataan, Intrepid, Yorktown, and Langley) that were located just east of Okinawa. The aircraft consisted of F6F Hellcat fighters, SB2C Helldiver dive-bombers, and TBF Avenger torpedo bombers. A force of six battleships (Massachusetts, Indiana, New Jersey, South Dakota, Wisconsin, and Missouri), supported by cruisers (including Alaska and Guam) and destroyers, was also assembled to intercept the Japanese fleet if the airstrikes did not succeed.
Since the Japanese force did not have air cover, the U.S. aircraft were able to set up for their attacks without fear of opposition from Japanese aircraft. U.S. attack aircraft arriving over the Yamato group, after their two-hour flight from Okinawa, were thus able to circle the Japanese ship formation just out of anti-aircraft range, methodically setting up their attacks on the warships below.
The first wave of U.S. carrier aircraft engaged the Japanese ships starting at 12:30. The Japanese ships increased speed to , began evasive maneuvers, and opened fire with their anti-aircraft guns. Yamato carried almost 150 anti-aircraft guns, including her massive 460 mm guns which could fire special "Common Type 3" anti-aircraft shells. The U.S. torpedo airplanes mainly attacked from the port side so that if the torpedoes mainly hit from that side, it would increase the likelihood of the target ship capsizing.
At 12:46, a torpedo hit Yahagi directly in her engine room, killing the entire engineering room crew and bringing her to a complete stop. Yahagi was hit by at least six more torpedoes and 12 bombs by succeeding waves of air attacks. Japanese destroyer Isokaze attempted to come to Yahagi's aid but was attacked, heavily damaged, and sank sometime later. Yahagi capsized and sank at 14:05. Her survivors, left floating in the water, could see the Yamato in the distance, still apparently steaming south and fighting attacking U.S. aircraft. However, in reality, Yamato was only minutes away from sinking.
During the first attack wave, despite intensive evasive maneuvers that caused most of the bombs and torpedoes aimed at her to miss, Yamato was hit by two armor-piercing bombs and one torpedo. Her speed was not affected, but one of the bombs started a fire aft of the superstructure that was not extinguished. Also, during the first attack wave, Japanese destroyers Hamakaze and Suzutsuki were heavily damaged and taken out of the battle. Hamakaze sank later.
Between 13:20 and 14:15, the second and third waves of U.S. aircraft attacked, heavily concentrating on the Yamato. During this time, Yamato was hit by at least eight torpedoes and up to 15 bombs. The bombs did extensive damage to the topside of the ship, including knocking out power to the gun directors and forcing the anti-aircraft guns to be individually and manually aimed and fired, greatly reducing their effectiveness. The torpedo hits, almost all on the port side, caused the Yamato to list enough that capsizing was now an imminent danger. The water damage-control station had been destroyed by a bomb hit making it impossible to counter-flood the specially designed spaces within the ship's hull to counteract hull damage. At 13:33 in a desperate attempt to keep the ship from capsizing, Yamato's damage control team counter-flooded both starboard engine and boiler rooms. This mitigated the danger but also drowned the several hundred crewmen manning those stations, who were given no notice that their compartments were about to fill with water. The lives of those crewmen bought Yamato about 30 more minutes afloat. The loss of the starboard engines, plus the weight of the water, caused Yamato to slow to about 10 knots.
With Yamato proceeding more slowly and therefore easier to target, U.S. torpedo aircraft concentrated on hitting her rudder and stern with torpedoes in order to affect her steering ability, which they succeeded in doing. At 14:02, after being informed that the ship could no longer steer and was unavoidably sinking, Admiral Ito ordered the mission canceled, the crew to abandon ship, and for the remaining ships to begin rescuing survivors. Yamato communicated this message to the other surviving ships by signal flag since her radios had been destroyed.
At 14:05, Yamato was stopped dead in the water and began to capsize. Admiral Ito and the captain refused to abandon her with the rest of the survivors. At 14:20, Yamato capsized completely and began to sink (). At 14:23, she suddenly blew up with an explosion so large that it was reportedly heard and seen 200 km away in Kagoshima and sent up a mushroom-shaped cloud almost 20,000 feet into the air. It is claimed that her large explosion downed several U.S planes observing her end. The explosion is believed to have occurred when the fires ignited by bomb hits reached the main magazines.
Attempting to make it back to port, Japanese destroyer Asashimo was bombed and sunk with all hands by U.S. aircraft. The Japanese destroyer Kasumi was also sunk by U.S. carrier aircraft attack during the battle. Suzutsuki, despite her bow being blown off, was able to make it to Sasebo, Japan, by steaming in reverse the entire way.
The remaining three less-damaged Japanese destroyers (Fuyuzuki, Yukikaze, and Hatsushimo) were able to rescue 280 survivors from Yamato (out of a crew of 2,700), plus 555 survivors from Yahagi (out of a crew of 1,000) and just over 800 survivors from Isokaze, Hamakaze, and Kasumi. However, 3,700 Japanese naval personnel perished in the battle. The ships took the survivors to Sasebo.
A total of 10 U.S. aircraft were shot down by anti-aircraft fire from the Japanese ships; some of the aircrews were rescued by amphibious aircraft or submarine. In total, the U.S. lost 12 men. Some of the Japanese survivors reported that U.S. fighter aircraft machine-gunned Japanese survivors floating in the water. Japanese survivors also reported that U.S. aircraft temporarily halted their attacks on the Japanese destroyers during the time that the destroyers were busy picking up survivors from the water.
During the battle, the Japanese Army conducted an air attack on the U.S. naval fleet at Okinawa as promised, but they failed to sink any ships. Around 115 aircraft, many of them kamikaze, attacked the U.S. ships throughout the day of April 7. Kamikaze aircraft hit Hancock, battleship Maryland, and destroyer Bennett, causing moderate damage to Hancock and Maryland and heavy damage to Bennett. About 100 of the Japanese aircraft were lost in the attack.
Ten-Go was the last major Japanese naval operation of the war, and the remaining Japanese warships had little involvement in combat operations for the rest of the conflict. Suzutsuki was never repaired. Fuyuzuki was repaired but hit a U.S. air-dropped mine at Moji, Japan, on August 20, 1945, and was not subsequently repaired. Yukikaze survived the war almost undamaged. Hatsushimo hit a U.S. air-dropped mine on July 30, 1945, near Maizuru, Japan, and was the 129th, and last, Japanese destroyer sunk in the war.
Okinawa was declared secure by Allied forces on June 21, 1945, after an intense and costly battle. Japan surrendered in August 1945, after being bombed twice with atomic weapons. The apparent willingness of Japan to sacrifice so many of its people using suicidal tactics such as Operation Ten-Go and in the Battle of Okinawa reportedly was a factor in the Allied decision to employ atomic weapons against Japan.
Other commanders of the Imperial Japanese Navy had very negative feelings about the operation, believing that it was a waste of human life and fuel. Captain Atsushi Ōi, who commanded escort fleets, was critical as fuel and resources were diverted from his operation. As he was told that the aim of this operation was "the tradition and the glory of Navy," he shouted:
This war is of our nation and why should the honor of our "surface fleet" be more respected? Who cares about their glory? Bakayaroh! (Damn fools!)The story of Operation Ten-Go is revered to some degree in modern Japan as evidenced by appearances of the story in popular Japanese culture which usually portray the event as a brave, selfless, but futile, symbolic effort by the participating Japanese sailors to defend their homeland . One of the reasons the event may have such significance in Japanese culture is that the word Yamato was often used as a poetic name for Japan. Thus, the end of battleship Yamato could serve as a metaphor for the end of the Japanese empire.
- ("Surface fleet" refers to capital ships, especially battleships that "should have won the war".)