Operation Hailstone (Japanese : トラック島空襲, translit. Torakku-tō Kūshū), lit. "the airstrike on Truk Island"), 17–18 February 1944, was a massive United States Navy air and surface attack on Truk Lagoon conducted as part of the American offensive drive against the Imperial Japanese Navy (IJN) through the Central Pacific Ocean during World War II.
Japanese is an East Asian language spoken by about 128 million people, primarily in Japan, where it is the national language. It is a member of the Japonic language family, and its relation to other languages, such as Korean, is debated. Japanese has been grouped with language families such as Ainu, Austroasiatic, and the now-discredited Altaic, but none of these proposals has gained widespread acceptance.
The romanization of Japanese is the use of Latin script to write the Japanese language. This method of writing is sometimes referred to in Japanese as rōmaji(ローマ字, literally, "Roman letters") ([ɾoːmaꜜʑi]. There are several different romanization systems. The three main ones are Hepburn romanization, Kunrei-shiki romanization, and Nihon-shiki romanization. Variants of the Hepburn system are the most widely used.
The United States Navy (USN) is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. It is the largest and most capable navy in the world and it has been estimated that in terms of tonnage of its active battle fleet alone, it is larger than the next 13 navies combined, which includes 11 U.S. allies or partner nations. with the highest combined battle fleet tonnage and the world's largest aircraft carrier fleet, with eleven in service, and two new carriers under construction. With 319,421 personnel on active duty and 99,616 in the Ready Reserve, the Navy is the third largest of the service branches. It has 282 deployable combat vessels and more than 3,700 operational aircraft as of March 2018, making it the second-largest air force in the world, after the United States Air Force.
Prior to Operation Hailstone, the IJN had used Truk as an anchorage for its large Combined Fleet. The coral atoll surrounding Truk's islands created a safe harbor where the few points of ingress and egress had been fortified by the Japanese with shore batteries, antiaircraft guns, and airfields.
Combined Fleet was the main ocean-going component of the Imperial Japanese Navy. Until 1933, Combined Fleet was not a permanent organization, but a temporary force formed for the duration of a conflict or major naval maneuvers from various units normally under separate commands in peacetime.
Artillery is a class of heavy military weapons built to fire munitions far beyond the range and power of infantry's small arms. Early artillery development focused on the ability to breach defensive walls, and fortifications during sieges, and led to heavy, fairly immobile siege engines. As technology improved, lighter, more mobile field artillery cannons developed for battlefield use. This development continues today; modern self-propelled artillery vehicles are highly mobile weapons of great versatility providing the large share of an army's total firepower.
American estimates of Truk's defenses and its role as a stronghold of the Japanese Navy led newspapers and military men to call it the "Gibraltar of the Pacific", or to compare it with Pearl Harbor. Truk's location in the Caroline Islands also made it an excellent shipping hub for armaments and aircraft moving from Japan's home islands down through the South Pacific Mandate and into the Japanese "Southern Resources Area".
Pearl Harbor is a lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. It has been long visited by the Naval fleet of the United States, before it was acquired from the Hawaiian Kingdom by the U.S. with the signing of the Reciprocity Treaty of 1875. Much of the harbor and surrounding lands is now a United States Navy deep-water naval base. It is also the headquarters of the United States Pacific Fleet. The U.S. government first obtained exclusive use of the inlet and the right to maintain a repair and coaling station for ships here in 1887. The attack on Pearl Harbor by the Empire of Japan on December 7, 1941, was the immediate cause of the United States' entry into World War II.
The Caroline Islands are a widely scattered archipelago of tiny islands in the western Pacific Ocean, to the north of New Guinea. Politically they are divided between the Federated States of Micronesia in the eastern part of the group, and Palau at the extreme western end. Historically, this area was also called Nuevas Filipinas or New Philippines as they were part of the Spanish East Indies and governed from Manila in the Philippines.
The South Pacific Mandate was a League of Nations mandate given to the Empire of Japan by the League of Nations following World War I. The South Pacific Mandate consisted of islands in the north Pacific Ocean that had been part of German New Guinea within the German colonial empire until they were occupied by Japan during World War I. Japan governed the islands under the mandate as part of the Japanese colonial empire until World War II, when the United States captured the islands. The islands then became the United Nations-established Trust Territory of the Pacific Islands governed by the United States. The islands are now part of Palau, Northern Mariana Islands, Federated States of Micronesia, and Marshall Islands.
By early 1944, Truk was increasingly unsustainable as a forward base of operations for the Japanese. To the west, American and Australian forces under General Douglas MacArthur had moved up through the Southwest Pacific, isolating or overrunning many Japanese strong points as part of Operation Cartwheel. The U.S. Navy, Marine Corps, and Army, under the command of Admiral Chester W. Nimitz, had overrun the most important islands in the nearby Gilbert Islands and Marshall Islands, and then built numerous air bases there.
Douglas MacArthur was an American five-star general and Field Marshal of the Philippine Army. He was Chief of Staff of the United States Army during the 1930s and played a prominent role in the Pacific theater during World War II. He received the Medal of Honor for his service in the Philippines Campaign, which made him and his father Arthur MacArthur Jr. the first father and son to be awarded the medal. He was one of only five to rise to the rank of General of the Army in the US Army, and the only one conferred the rank of field marshal in the Philippine Army.
Operation Cartwheel (1943–1944) was a major military operation for the Allies in the Pacific theatre of World War II. Cartwheel was an operation aimed at neutralising the major Japanese base at Rabaul. The operation was directed by the Supreme Allied Commander in the South West Pacific Area (SWPA), General Douglas MacArthur, whose forces had advanced along the northeast coast of New Guinea and occupied nearby islands. Allied forces from the Pacific Ocean Areas command, under Admiral Chester W. Nimitz, advanced through the Solomon Islands toward Bougainville. The Allied forces involved were from Australia, the Netherlands, New Zealand, the US and various Pacific Islands.
Chester William Nimitz, Sr. was a fleet admiral of the United States Navy. He played a major role in the naval history of World War II as Commander in Chief, U.S. Pacific Fleet and Commander in Chief, Pacific Ocean Areas, commanding Allied air, land, and sea forces during World War II.
As a result, the Japanese Navy had to relocate the Combined Fleet's forward base to the Palau Islands, and eventually to Indonesia, and the Fleet had begun clearing its major warships out of Truk before the Hailstone attack struck.
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia, between the Indian and Pacific oceans. It is the world's largest island country, with more than seventeen thousand islands, and at 1,904,569 square kilometres, the 14th largest by land area and the 7th largest in combined sea and land area. With over 261 million people, it is the world's 4th most populous country as well as the most populous Muslim-majority country. Java, the world's most populous island, is home to more than half of the country's population.
Nevertheless, the Hailstone attack on Truk caught a good number of Japanese auxiliary ships and cargo ships in the harbor, as well as some warships. Between the air attacks and surface ship attacks over the two days of Operation Hailstone, the worst blow against the Japanese was about 250 warplanes destroyed, with the concurrent irreplaceable loss of experienced pilots. Also, about forty ships — two light cruisers, four destroyers, nine auxiliary ships, and about two dozen cargo vessels — were sunk.
An auxiliary ship is a naval ship designed to operate in support of combatant ships and other naval operations. Auxiliaries are not primary combatants, although they may have some limited combat capacity, usually of a self-defence nature.
A cargo ship or freighter ship is a merchant ship that carries cargo, goods, and materials from one port to another. Thousands of cargo carriers ply the world's seas and oceans each year, handling the bulk of international trade. Cargo ships are usually specially designed for the task, often being equipped with cranes and other mechanisms to load and unload, and come in all sizes. Today, they are almost always built by welded steel, and with some exceptions generally have a life expectancy of 25 to 30 years before being scrapped.
A light cruiser is a type of small- or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck. Prior to this smaller cruisers had been of the protected cruiser model, possessing armored decks only. While lighter and smaller than other contemporary ships they were still true cruisers, retaining the extended radius of action and self-sufficiency to act independently across the world. Through their history they served in a variety of roles, primarily as convoy escorts and destroyer command ships, but also as scouts and fleet support vessels for battle fleets.
Considerable damage was inflicted on the various island bases, including dockyards, communications centers, supply dumps, and its submarine base. Truk remained effectively isolated for the remainder of the war, cut off and surrounded by the American island hopping campaign in the Central Pacific, which also bypassed important Japanese garrisons and airfields in the Bismarck Archipelago, the Caroline Islands, the Marshalls, and the Palaus. Meanwhile, the Americans built new bases from scratch at places like the Admiralty Islands, Majuro, and Ulithi Atoll, and took over the major port at Guam.
The Japanese occupied Micronesia, including the Caroline Islands, in 1914, and established Truk as a base as early as 1939. The lagoon was first built up to house the IJN's 4th Fleet, its "South Seas Force". After the outbreak of war with the United States, the 4th Fleet was put under the command of the Combined Fleet, which continued to use Truk as a forward operating base into 1944. In addition to anchorages for warships, and port facilities for shipping between the home islands and the Southern Resources Area, five airfields and a seaplane base were constructed at Truk, making it the only major Japanese airfield within flying range of the Marshall Islands.
Despite the impressions of U.S. Navy leaders and the American public concerning Truk's projected fortifications, the base was never significantly reinforced or protected against land attack. In fact, the development of Truk only began in concert, and in hurried fashion in late 1943, when the airfields were extended, shore batteries were erected, and other defensive measures taken against a U.S. invasion .
Because aircraft stationed at Truk could potentially interfere with the upcoming invasion of Eniwetok, and because Truk had recently served as a ferry point for the resupply of aircraft to Rabaul, Admiral Raymond Spruance ordered Vice Admiral Marc A. Mitscher's Task Force 58 (TF 58) to carry out air raids against Truk. Three of TF 58's four carrier task groups (TGs) were committed to the operation. Their total strength consisted of five fleet carriers (the Enterprise, Yorktown, Essex, Intrepid, and Bunker Hill) and four light carriers (the Belleau Wood, Cabot, Monterey, and Cowpens), carrying a total of 500+ warplanes. Supporting these aircraft carriers was a task force of seven battleships, and numerous heavy cruisers, light cruisers, destroyers, and submarines.
The Japanese, meanwhile, understood the weakness of their position at Truk. The IJN had begun withdrawing fleet units from its anchorages as early as October 1943. The effective abandonment of Truk as a forward operating base accelerated during the first week of February 1944, following Japanese sightings of U.S. Marine Corps PB4Y-1 Liberator reconnaissance planes sent to reconnoiter the area.
The three carrier task groups committed to Hailstone moved into position and began launching their first fighter sweep 90 minutes before daybreak on 17 February 1944. No Japanese air patrol was active at the time as the IJN's 22nd and 26th Air Flotillas were enjoying shore leave after weeks on high alert following the Liberator sightings.Similarly problematic for the Japanese, radar on Truk was not capable of detecting low-flying planes — a weakness probably known and exploited by Allied intelligence organizations. Because of these factors, U.S. carrier aircraft achieved total surprise.
Japanese pilots scrambled into their cockpits just minutes before TF 58 planes arrived over Eten, Param, Moen and Dublon islands. Though there were more than 300 Imperial Japanese Navy Air Service (IJNAS) and Imperial Japanese Army Air Service (IJAAS) planes present at Truk on the first day of attacks, only about half of them were operational compared with over 500 operational aircraft among the carriers of TF 58. U.S. Navy fighter pilots in their Grumman F6F Hellcats, with the advantages of speed, altitude and surprise, achieved a one–sided victory against IJNAF pilots flying the inferior Mitsubishi A6M Zero. As many as 30 of the 80 Zeros sent up in response to the fighter sweep were shot down, compared with four Hellcats reported lost. Only token aerial resistance was encountered for the rest of the morning; almost no Japanese aircraft were present by the afternoon.
Due to the lack of air cover or warning, many merchant ships were caught at anchor with only the islands' anti-aircraft guns for defense against the U.S. carrier planes. Some vessels outside the lagoon already steaming towards Japan were attacked by U.S. submarines and sunk before they could make their escape. Still others, attempting to flee via the atoll's North Pass, were bottled up by aerial attack and by Admiral Spruance's surface force, Task Group 50.9, which circumnavigated Truk bombarding shore positions and engaging enemy ships.
Torpedo bomber and dive bomber squadrons from the carrier air groups (CAGs) were responsible for the bulk of the damage inflicted on Japanese ground facilities. Early on the first day of Hailstone, Grumman TBF Avenger torpedo bomber squadrons from Enterprise's Air Group 10 (CAG-10) and Intrepid's CAG-6 dropped fragmentation and incendiary bombs on runways at Eten Island as well as the seaplane base on Moen Island. Dozens of aircraft were damaged or destroyed, further blunting any possible response by the Japanese to the strikes. Subsequent joint attacks by dive bombers and Avenger torpedo bombers cratered runways and destroyed hangar facilities.
Morning strikes were also launched against shipping targets in the lagoon. Lieutenant Commander (later Rear Admiral) James D. Ramage, commanding officer of Dive Bombing Squadron 10 (VB-10), is credited with sinking the previously damaged merchant tanker Hoyo Maru. 's Torpedo Squadron 6 (VT-6) Avengers scored a direct hit on the ammunition ship Aikoku Maru. The bomb blast set off a tremendous explosion, which immediately sank the ship and apparently engulfed the plane as well, killing all three men inside.Lieutenant James E. Bridges and his crew in one of Intrepid
By the second and third anti-shipping strikes of the day, carrier air group action reports listed the apparent enemy mission as "escape". 's dive and torpedo bombing squadrons claimed two hits on Katori and hits on another cruiser and multiple destroyers; Essex bombers claimed five hits on a Katori-class cruiser as well, stating that the ship was stopped dead in the water after the attack.Those ships able to make for open sea steamed for the North Pass exit from the lagoon while weathering repeated aerial attacks. One particular group of warships—cruiser Katori, auxiliary cruiser Akagi Maru , destroyers Maikaze, Nowaki and minesweeper Shonan Maru—was given special attention by carrier bombers. Multiple air groups attacked these ships, inflicting serious damage. Yorktown
At this point reports reached Admiral Spruance concerning the group of warships fleeing through North Pass. The admiral put himself in tactical command of Task Group 50.9, made up of four destroyers, two heavy cruisers and the battleships Iowa and New Jersey, which he personally led in a surface engagement against the previously damaged Japanese ships. Spruance was so adamant on engaging in ship-to-ship combat that his carrier commander, Admiral Mitscher, ordered his air groups to stop attacking Katori and her companions.
The battered Japanese ships did not stand much of a chance against Task Group 50.9, though members of his staff saw Spruance's decision to engage in surface action when aircraft likely could have achieved similar results as needlessly reckless. Indeed, the Japanese destroyer Maikaze managed to fire torpedoes at the battleship New Jersey during the engagement. Fortunately for Spruance, the torpedoes missed, and the "battle" ended with predictably one–sided results. The U.S. Navy surface combatants incurred virtually no damage. The IJN lost Maikaze, Shonan Maru, Katori and Akagi Maru. Destroyer Nowaki was the only Japanese ship from this group to escape.
Retaliation for the day's strikes arrived late at night in the form of small groups of Japanese bombers probing the task groups' defenses. From roughly 21:00, on 17 February, to just minutes past midnight on 18 February, at least five groups of between one and three enemy planes attempted to sneak past screening ships to strike at the fleet carriers. One such plane, a Nakajima B5N2 "Kate" bomber, managed to evade night fighter planes protecting the U.S. task force and dropped its torpedo on Task Group 58.2. The torpedo struck Intrepid on the starboard quarter of the ship, damaging steering control and killing 11 sailors. Intrepid was forced to retire to the U.S. for repairs and did not return to combat until August 1944.
Truk, like so many other Japanese bases, was left to itself without hope of resupply or reinforcement. Army forces which had arrived at the atoll before the U.S. attacks put increasing strain on available foodstuffs and medical supplies. Dwindling ammunition even limited the ability of shore batteries to fend off intermittent attacks by Allied forces, including experimental raids by Boeing B-29 Superfortresses and attacks by Allied carrier aircraft.
Losses at Truk were severe. Some 17,000 tons of stored fuel were destroyed by the strikes.Shipping losses totaled almost 200,000 tons including precious resources in fleet oilers. This represents almost one tenth of total Japanese shipping losses between 1 November 1943 and 30 June 1944. Moreover, the isolation of this whole area of operations by submarine and air attack began the effective severance of Japanese shipping lanes between empire waters and critical fuel supplies to the south. The ultimate effect of such a disconnect was later seen during the Battle of Leyte Gulf, when IJN forces had to sortie separately from Japan and Lingga Roads due to fuel constraints. The neutralization of Truk, and the seizure of Eniwetok, paved the way for the upcoming invasion of Saipan, which for the first time put U.S. land-based heavy bombers within range of the Japanese home islands.
Truk is renowned today as a tourist destination for divers interested in seeing the many shipwrecks left in the lagoon, many of which were caused by the Operation Hailstone strikes.
List derived from Jeffery's War Graves, Munition Dumps and Pleasure Grounds (2007)
CL Katori (香取) 5,800 tons
CL Naka (那珂) 5,195 tons
DD Maikaze (舞風) 陽炎型 2,000 tons
DD Fumizuki (文月) 睦月型 1,320 tons
DD Oite (追風) 神風型 1,270 tons
DD Tachikaze (太刀風) 峯風型 1,215 tons
Submarine chaser CH-29, 440 tons
Submarine chaser CH-24, 440 tons
Auxiliary submarine chaser Shonan Maru #15 (第15昭南丸), 355 tons
Motor torpedo boat #10, 85 tons
Repair ship Akashi (明石) 10,500 tons
Seaplane tender Akitsushima (秋津洲) 4,650 tons
DD Matsukaze (松風) 神風型 1,400 tons
DD Shigure (時雨) 白露型 1,685 tons
Submarine I-10 (伊10), 2,919 tons
Submarine RO-42, 1,115 tons
Submarine chaser CHa-20
Target ship Hakachi (波勝) 1,641 tons
List derived from Jeffery's War Graves, Munition Dumps and Pleasure Grounds (2007)
Auxiliary cruiser Aikoku Maru (爱国丸) 10,348 tons
Auxiliary cruiser Akagi Maru (赤城丸) 7,367 tons
Auxiliary cruiser Kiyosumi Maru (清澄丸) 6,983 tons
Navy transport Hoki Maru (伯耆丸) 7,112 tons
Navy transport Yamagiri Maru (山霧丸) 7,112 tons
Navy transport Fujikawa Maru (富士川丸) 6,938 tons
Navy transport/freighter San Francisco Maru (桑港丸) 5,831 tons
Navy transport Reiyo Maru (麗洋丸) 5,446 tons
Navy transport Seiko Maru (西江丸)? 5,385 tons
Navy transport/passenger/cargo ship Kensho Maru (乾祥丸) 4,862 tons
Navy transport/freighter Hanakawa Maru (花川丸) 4,739 tons
Navy transport/passenger/cargo ship Sankisan Maru or Yamakisan Maru (山鬼山丸) 4,776 tons
Navy transport/freighter Hokuyo Maru (北洋丸) 4,217 tons
Navy transport/freighter Momokawa Maru (桃川丸) 3,829 tons
Navy water carrier/passenger/cargo ship Nippo Maru (日豊丸) 3,764 tons
Navy transport/freighter Unkai Maru #6(第六雲海丸) 3,220 tons
Navy transport Taiho Maru (大邦丸) 2,827 tons
Navy transport/freighter Shotan Maru (松丹丸) 1,999 tons
Navy transport/freighter Gosei Maru (五星丸) 1,931 tons
Freighter Taikichi Maru or Tachi Maru (泰吉丸) 1,891 tons
Army transport Gyoten Maru (暁天丸) 6,854 tons
Army transport/freighter Nagano Maru (長野丸) 3,824 tons
Army transport Yubae Maru (夕映丸) 3,217 tons
Submarine tender Heian Maru (平安丸) 11,614 tons
Submarine tender Rio de Janeiro Maru (リオデジャネイロ丸) 9,626 tons
Fleet oiler Shinkoku Maru (神国丸) 10,020 tons
Oil tanker Fujisan Maru (富士山丸) 9,524 tons
Auxiliary oil tanker/whaler Tonan Maru #3 (第三図南丸) 19,209 tons
Auxiliary oil tanker Houyou Maru or Hoyo Maru (宝洋丸) 8,691 tons
Auxiliary oil tanker/passenger/cargo ship Amagisan Maru (天城山丸) 7,620 tons
Cargo ship Sōya (宗谷) 3,800 tons
Myōkō (妙高) was the lead ship of the four-member Myōkō class of heavy cruisers of the Imperial Japanese Navy (IJN), which were active in World War II. She was named after Mount Myōkō in Niigata Prefecture. The other ships of the class were Nachi, Ashigara, and Haguro.
USS Haddock (SS-231), a Gato-class submarine, was the second submarine of the United States Navy to be named for the haddock, a small edible Atlantic fish, related to the cod. A previous submarine had been named Haddock (SS-32), but was renamed K-1 prior to her launching, so Haddock (SS-231) was the first to actually bear the name.
Tenryū (天龍) was the lead ship in the two-ship Tenryū class of light cruisers of the Imperial Japanese Navy. Tenryū was named after the Tenryū River in Nagano and Shizuoka prefectures.
Naka (那珂) was a Sendai-class light cruiser in the Imperial Japanese Navy (IJN), named after the Naka River in the Tochigi and Ibaraki prefectures of eastern Japan. Naka was the third vessel completed in the Sendai class of light cruisers, and like other vessels of her class, she was intended for use as the flagship of a destroyer flotilla.
Kumano (熊野) was one of four Mogami class of heavy cruisers in the Imperial Japanese Navy, serving in World War II. She was named after the Kumano River Kii Peninsula on the island of Honshu in central Japan. The Mogami-class ships were constructed as "light cruisers" with five triple 6.1-inch dual purpose guns. They were exceptionally large for light cruisers, and the barbettes for the main battery were designed for quick refitting with twin 8-inch guns. In 1937 all four ships were "converted" to heavy cruisers in this fashion. Kumano served in numerous combat engagements in the Pacific War, until she was eventually sunk by carrier aircraft from Task Force 38 while she was undergoing repairs at Santa Cruz, Philippines in November, 1944.
Yura (由良) was the fourth of the six ships completed in the Nagara class of light cruisers for the Imperial Japanese Navy (IJN), and like other vessels of her class, she was intended for use as the flagship of a destroyer flotilla. She was named after the Yura River near Kyoto, Japan. She served in the early stages of World War II, and was the first Japanese light cruiser to be lost in that conflict.
Hiyō was the name ship of her class of two aircraft carriers of the Imperial Japanese Navy (IJN). Begun as the ocean liner Izumo Maru (出雲丸) in 1939, she was purchased by the Navy Ministry in 1941 for conversion to an aircraft carrier. Completed shortly after the Battle of Midway in June 1942, she participated in the Guadalcanal Campaign, but missed the Battle of the Santa Cruz Islands in October because of an electrical generator fire.
Nagara (長良) was the lead ship of her class of light cruiser in the Imperial Japanese Navy. She was named after the Nagara River in the Chūbu region of Japan.
Isuzu (五十鈴) was the second of six vessels in the Nagara class of light cruisers, and like other vessels of her class, she was intended for use as the flagship of a destroyer flotilla. She was named after the Isuzu River, near Ise Shrine in the Chūbu region of Japan. She saw action during World War II in the Battle of Hong Kong and in the Solomon Islands campaign, and the Battle of Leyte Gulf before being sunk by American submarines in the Netherlands East Indies in April 1945.
Katori (香取) was the lead ship of the Katori class of three light cruisers which served with the Imperial Japanese Navy during World War II. The ship was named after the noted Shinto Katori Shrine in Chiba prefecture, Japan.
Kagerō was the lead ship of the 19-vessel Kagerō-class destroyers built for the Imperial Japanese Navy in the late-1930s under the Circle Three Supplementary Naval Expansion Program.
Shigure was the second of ten Shiratsuyu-class destroyers, and the first to be built for the Imperial Japanese Navy under the Circle One Program. Along with the destroyer Yukikaze, she developed a reputation within the Imperial Japanese Navy for being "lucky" or "unsinkable", emerging undamaged from several battles and as the sole surviving Japanese warship from two. As the flagship of Captain Tameichi Hara's Destroyer Division 27 Shigure received a prominent place in the memoirs of the only Japanese destroyer captain to survive the entire Pacific War. Shigure was torpedoed and sunk by the submarine USS Blackfin in the Gulf of Siam on 24 January 1945.
Un'yō was a Taiyō-class escort carrier originally built as Yawata Maru (八幡丸), one of three Nitta Maru-class cargo liners built in Japan during the late 1930s. She was transferred to the Imperial Japanese Navy (IJN) during the Pacific War, renamed, and was converted into an escort carrier in 1942. The ship spent most of her service ferrying aircraft, cargo and passengers to various bases in the Pacific. Un'yō was badly damaged by an American submarine in early 1944. After repairs were completed in June, the ship resumed transporting aircraft and cargo. During a return voyage from Singapore in September, she was sunk by the submarine USS Barb.
The 4th Fleet was a fleet of the Imperial Japanese Navy. The Fourth Fleet designation was used during three separate periods. The initial designation was for a group of ships that were assigned to work together during the Russo-Japanese conflict and the period of its immediate aftermath. The second time the designation was used was during the Sino-Japanese conflict, and the third time was as a South Pacific area of command during the middle of the Pacific War.
Kongō Maru (金剛丸) was an 8,624 gross ton passenger-cargo ship built by Harima Shipbuilding Company in Japan for Kokusai Kisen Kabushiki Kaisha in 1935. She was requisitioned by the Imperial Japanese Navy during the Second World War and converted to an armed merchant cruiser.
Fujikawa Maru was a cargo ship originally built in 1938 for the Toyo Kaiun Kisen Kaisha and was requisitioned by the Imperial Japanese Navy during World War II for use as an armed aircraft transport or ferry. She was sunk in Truk Lagoon in 1944 during Operation Hailstone and is now a leading wreck diving site for scuba divers.
Aikoku Maru (愛国丸) was an armed merchant cruiser of the Imperial Japanese Navy in World War II. The ship entered service in 1940, the ship was later converted to an ammunition ship. She was destroyed in February 1944.
Heian Maru (平安丸) was a Japanese ocean liner launched in 1930 and operated primarily on the NYK line's trans-Pacific service between Yokohama and Seattle. Shortly before the outbreak of the Pacific War, it was requisitioned by the Imperial Japanese Navy and converted to use as an auxiliary submarine tender. In 1944 it was sunk by American aircraft at Chuuk Lagoon during Operation Hailstorm. Its submerged hulk – the largest of Chuuk's "Ghost Fleet" – remains a popular scuba diving destination.
The Akagi Maru-class armed merchant cruiser was a class of three armed merchant cruisers of the Imperial Japanese Navy.
Akagi Maru was one of three Akagi Maru-class armed merchantmen of the Imperial Japanese Navy, and was launched in 1936. Akagi Maru was used initially used as a refrigerated cargo/passenger ship between ports in Japan, Europe and South America. The ship took part in World War II in the Pacific Ocean and was sunk with great loss of life by air attack on 17 February 1944 in Chuuk Lagoon as a part of the Allied Operation Hailstone.
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