Operation Hailstone ( ja, トラック島空襲, Torakku-tō Kūshū, lit=airstrike on Truk Island), 17–18 February 1944, was a massive

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

air and surface attack on Truk Lagoon conducted as part of the American offensive drive against the

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrend ...

(IJN) through the Central Pacific Ocean during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. Prior to Operation Hailstone, the IJN had used Truk as an anchorage for its large

Combined Fleet The was the main sea-going component of the Imperial Japanese Navy. Until 1933, the 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 norm ...

. 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 In military organizations, an artillery battery is a unit or multiple systems of artillery, mortar systems, rocket artillery, multiple rocket launchers, surface-to-surface missiles, ballistic missiles, cruise missiles, etc., so grouped to facil ...

, antiaircraft guns, and

airfield An aerodrome ( Commonwealth English) or airdrome (American English) is a location from which aircraft flight operations take place, regardless of whether they involve air cargo, passengers, or neither, and regardless of whether it is for pub ...

s. 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 Pearl Harbor is an American lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. It was often 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 R ...

. Truk's location in the

Caroline Islands The Caroline Islands (or the Carolines) 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 (FSM) in the ce ...

also made it an excellent shipping hub for armaments and

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engine ...

moving from Japan's home islands down through the South Seas Mandate and into the Japanese "Southern Resources Area". 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 Operation Cartwheel (1943–1944) was a major military operation for the Allies of World War II, Allies in the Pacific War, Pacific theatre of World War II. Cartwheel was an operation aimed at neutralising the major Empire of Japan, Japanes ...

. 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 The Marshall Islands ( mh, Ṃajeḷ), officially the Republic of the Marshall Islands ( mh, Aolepān Aorōkin Ṃajeḷ),'' () is an independent island country and microstate near the Equator in the Pacific Ocean, slightly west of the Intern ...

, and then built numerous

air base An air base (sometimes referred to as a military air base, military airfield, military airport, air station, naval air station, air force station, or air force base) is an aerodrome used as a military base by a military force for the operation ...

s there. As a result, the Japanese Navy had to relocate the Combined Fleet's forward base to the

Palau Islands Palau,, officially the Republic of Palau and historically ''Belau'', ''Palaos'' or ''Pelew'', is an island country and microstate in the western Pacific. The nation has approximately 340 islands and connects the western chain of the Caro ...

, and eventually to

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

, and the Fleet had begun clearing its major warships – carriers, battleships, and heavy cruisers – out of Truk before the ''Hailstone'' attack struck. Nevertheless, the ''Hailstone'' attack on Truk caught a good number of Japanese

auxiliary ship An auxiliary ship is a naval ship designed to support combatant ships and other naval operations. Auxiliary ships are not primary combatant vessels, though they may have some limited combat capacity, usually for purposes of self-defense. Auxil ...

s and cargo ships in the harbor, as well as some smaller 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

warplane A military aircraft is any fixed-wing or rotary-wing aircraft that is operated by a legal or insurrectionary armed service of any type. Military aircraft can be either combat or non-combat: * Combat aircraft are designed to destroy enemy equi ...

s destroyed, with the concurrent loss of irreplaceable experienced pilots, and 17,000 tons of stored fuel. Also, about forty ships – two

light cruiser 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 th ...

s, four destroyers, nine auxiliary ships, and about two dozen cargo vessels – were sunk. 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 Leapfrogging, also known as island hopping, was a military strategy employed by the Allies in the Pacific War against the Empire of Japan during World War II. The key idea is to bypass heavily fortified enemy islands instead of trying to captu ...

campaign in the Central Pacific, which also bypassed important Japanese garrisons and airfields in the Bismarck Archipelago, the

, the Marshalls, and the Palaus. Meanwhile, the Americans built new bases from scratch at places like the

Admiralty Islands The Admiralty Islands are an archipelago group of 18 islands in the Bismarck Archipelago, to the north of New Guinea in the South Pacific Ocean. These are also sometimes called the Manus Islands, after the largest island. These rainforest-co ...

Majuro Majuro (; Marshallese: ' ) is the capital and largest city of the Marshall Islands. It is also a large coral atoll of 64 islands in the Pacific Ocean. It forms a legislative district of the Ratak (Sunrise) Chain of the Marshall Islands. The ato ...

, and

Ulithi Atoll Ulithi ( yap, Wulthiy, , or ) is an atoll in the Caroline Islands of the western Pacific Ocean, about east of Yap. Overview Ulithi consists of 40 islets totaling , surrounding a lagoon about long and up to wide—at one of the largest ...

, and took over the major port at

Guam Guam (; ch, Guåhan ) is an organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. It is the westernmost point and territory of the United States (reckoned from the geographic cent ...

Background

The Japanese occupied

Micronesia Micronesia (, ) is a subregion of Oceania, consisting of about 2,000 small islands in the western Pacific Ocean. It has a close shared cultural history with three other island regions: the Philippines to the west, Polynesia to the east, and ...

, 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

, 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

s and a

seaplane A seaplane is a powered fixed-wing aircraft capable of taking off and landing (alighting) on water.Gunston, "The Cambridge Aerospace Dictionary", 2009. Seaplanes are usually divided into two categories based on their technological characteri ...

base were constructed at Truk, making it the only major Japanese airfield within flying range of the

. 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 earnest and in hurried fashion in late 1943, when the airfields were extended,

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 Raymond Ames Spruance (July 3, 1886 – December 13, 1969) was a United States Navy admiral during World War II. He commanded U.S. naval forces during one of the most significant naval battles that took place in the Pacific Theatre: the Battle ...

ordered Vice Admiral Marc A. Mitscher's

Fast Carrier Task Force The Fast Carrier Task Force (TF 38 when assigned to Third Fleet, TF 58 when assigned to Fifth Fleet), was the main striking force of the United States Navy in the Pacific War from January 1944 through the end of the war in August 1945. The task ...

, designated 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 , , , , and ) and four light carriers (the , , , and ), carrying a total of 500+

s. Supporting these aircraft carriers was a task force of seven battleships, and numerous

heavy cruiser The heavy cruiser was a type of cruiser, a naval warship designed for long range and high speed, armed generally with naval guns of roughly 203 mm (8 inches) in caliber, whose design parameters were dictated by the Washington Naval T ...

s, 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 plane In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain, and other activities. Examples of reconnaissance include patrolling by troops (skirmishers, ...

s sent to reconnoiter the area.

Attack

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 The Imperial Japanese Army Air Service (IJAAS) or Imperial Japanese Army Air Force (IJAAF; ja, 大日本帝國陸軍航空部隊, Dainippon Teikoku Rikugun Kōkūbutai, lit=Greater Japan Empire Army Air Corps) was the aviation force of the Im ...

(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 Hellcat The Grumman F6F Hellcat is an American carrier-based fighter aircraft of World War II. Designed to replace the earlier F4F Wildcat and to counter the Japanese Mitsubishi A6M Zero, it was the United States Navy's dominant fighter in the second ha ...

s, with the advantages of speed, altitude, armour, and surprise, achieved a one–sided victory against IJNAS pilots flying the outdated

Mitsubishi A6M Zero The Mitsubishi A6M "Zero" is a long-range carrier-based fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries, and was operated by the Imperial Japanese Navy from 1940 to 1945. The A6M w ...

. 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 A torpedo bomber is a military aircraft designed primarily to attack ships with aerial torpedoes. Torpedo bombers came into existence just before the First World War almost as soon as aircraft were built that were capable of carrying the weight ...

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 The Grumman TBF Avenger (designated TBM for aircraft manufactured by General Motors) is an American World War II-era torpedo bomber developed initially for the United States Navy and Marine Corps, and eventually used by several air and naval a ...

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''. Lieutenant James E. Bridges and his crew in one of ''Intrepid''s Torpedo Squadron 6 (VT-6) Avengers scored a direct hit on the ammunition ship . 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. Japanese ammunition ship Aikoku Maru in Truk Harbor explodes

Japanese ammunition ship Aikoku Maru in Truk Harbor explodes

By the second and third anti-shipping strikes of the day, carrier air group action reports listed the apparent enemy mission as "escape". 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 ''Akagi Maru'' was one of three 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 ...

'', destroyers ''Maikaze'', ''Nowaki'' and minesweeper ''Shonan Maru''—was given special attention by carrier bombers. Multiple air groups attacked these ships, inflicting serious damage. ''Yorktown''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 as well, stating that the ship was stopped dead in the water after the attack. At this point reports reached Admiral Spruance concerning the group of warships fleeing through North Pass. 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 admiral put himself in tactical command of Task Group 50.9, made up of four destroyers, heavy cruisers ''Minneapolis'' and ''New Orleans'', and the new battleships and , which he personally led in a surface engagement against the previously damaged Japanese ships. 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, and it was the only time in their careers that ''Iowa'' and ''New Jersey'' had fired their main armament at enemy ships. 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.

Aftermath

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 represented 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 The Lingga Regency ( id, Kabupaten Lingga) is a group of islands in Indonesia, located south of Singapore, along both sides of the equator, off the eastern coast of Riau Province on Sumatra island. They are south of the populated Riau Archipela ...

due to fuel constraints. The neutralization of Truk, and the seizure of Eniwetok, paved the way for the upcoming

invasion of Saipan The Battle of Saipan was a battle of the Pacific campaign of World War II, fought on the island of Saipan in the Mariana Islands from 15 June to 9 July 1944 as part of Operation Forager. It has been referred to as the "Pacific D-Day" with the ...

, which for the first time put U.S. land-based heavy bombers within range of the Japanese home islands. Japan started to rebuild Truk as a bomber air base and increased its AA defenses. Spruance sent in carrier planes again on April 29, 1944, and destroyed AA and bombers parked at airports. British forces attacked again in June 1945. However there was no significant naval buildup at Truk after Operation Hailstone. Truk is renowned today as a tourist destination for divers interested in seeing the many shipwrecks left in the lagoon, many of which were sunk in Operation Hailstone.

List of ships in Truk at the time of attack

Warships

List derived from Jeffery's ''War Graves, Munition Dumps and Pleasure Grounds'' (2007)

Sunk

* Cruiser (CL) ** ''Katori'' (香取) 5,800 tons ** ''Naka'' (那珂) 5,195 tons * Destroyer (DD) ** 1 modern *** ''Maikaze'' (舞風) 陽炎型 2,000 tons ** 3 obsolescent *** ''Fumizuki'' (文月) 睦月型 1,320 tons *** ''Oite'' (追風) 神風型 1,270 tons *** ''Tachikaze'' (太刀風) 峯風型 1,215 tons * Submarine chaser ** ''CH-29'', 440 tons ** ''CH-24'', 440 tons * Auxiliary submarine chaser ''Shonan Maru'' #15 (第15昭南丸), 355 tons * Motor torpedo boat #10, 85 tons

Damaged

* Repair ship ''Akashi'' (明石) 10,500 tons * Seaplane tender ''Akitsushima'' (秋津洲) 4,650 tons * Destroyer (DD) ** ''Matsukaze'' (松風) 神風型 1,400 tons ** ''Shigure'' (時雨) 白露型 1,685 tons * Submarine ** ''I-10'' (伊10), 2,919 tons ** ''RO-42'', 1,115 tons * Submarine chaser ''CHa-20'' * Target ship ''Hakachi'' (波勝) 1,641 tons

Merchant ships

List derived from Jeffery's ''War Graves, Munition Dumps and Pleasure Grounds'' (2007)

Sunk

* Auxiliary cruiser ** ''Aikoku Maru'' (愛国丸) 10,348 tons ** ''

'' (赤城丸) 7,367 tons ** ''Kiyosumi Maru'' (清澄丸) 6,983 tons * Navy transport ** ''Hoki Maru'' (伯耆丸) 7,112 tons ** ''Yamagiri Maru'' (山霧丸) 7,112 tons ** '' Fujikawa Maru'' (富士川丸) 6,938 tons ** Navy transport/freighter ''San Francisco Maru'' (桑港丸) 5,831 tons ** ''Reiyo Maru'' (麗洋丸) 5,446 tons ** ''Seiko Maru'' (西江丸)? 5,385 tons ** passenger/cargo ship ''Kensho Maru'' (乾祥丸) 4,862 tons ** freighter ''Hanakawa Maru'' (花川丸) 4,739 tons ** passenger/cargo ship ''Sankisan Maru'' or ''Yamakisan Maru'' (山鬼山丸) 4,776 tons ** freighter ''Hokuyo Maru'' (北洋丸) 4,217 tons ** freighter ''Momokawa Maru'' (桃川丸) 3,829 tons ** Navy water carrier/passenger/cargo ship ''Nippo Maru'' (日豊丸) 3,764 tons ** freighter ''Unkai Maru #6''(第六雲海丸) 3,220 tons ** ''Taiho Maru'' (大邦丸) 2,827 tons ** freighter ''Shotan Maru'' (松丹丸) 1,999 tons ** 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 ** freighter ''Nagano Maru'' (長野丸) 3,824 tons ** ''Yubae Maru'' (夕映丸) 3,217 tons * Submarine tender ** '' Heian Maru'' (平安丸) 11,614 tons ** ''Rio de Janeiro Maru'' (リオデジャネイロ丸) 9,626 tons * Oiler ** 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 ** ''Houyou Maru'' or ''Hoyo Maru'' (宝洋丸) 8,691 tons ** passenger/cargo ship ''Amagisan Maru'' (天城山丸) 7,620 tons

Damaged

* Cargo ship ''Sōya'' (宗谷) 3,800 tons

Footnotes

Citations

References

Bibliography

* * * * * * * * * * * * * *

Primary sources

* * * * * *

External links

* * * * * {{DEFAULTSORT:Hailstone, Operation Pacific Ocean theatre of World War II History of the Federated States of Micronesia South Seas Mandate in World War II Articles containing video clips February 1944 events Naval battles of World War II involving the United States World War II aerial operations and battles of the Pacific theatre

Background

Attack

Aftermath

List of ships in Truk at the time of attack

Warships

Sunk

Damaged

Merchant ships

Sunk

Damaged

See also

Footnotes

Citations

References

Bibliography

Primary sources

Further reading

Video

External links