Operation Hailstone

Operation Hailstone (known in Japan as トラック島空襲 Torakku-tō Kūshū, lit. "the airstrike on Truk Island") was a massive naval air and surface attack launched on February 16–17, 1944, during World War II by the United States Navy against the Japanese naval and air base at Truk in the Caroline Islands, a pre-war Japanese territory.

Background
Truk was a major Japanese logistical base as well as the operating "home" base for the Imperial Japanese Navy's Combined Fleet. Some have described it as the Japanese equivalent of the US Navy's Pearl Harbor. The atoll was the only major Japanese airbase within range of the Marshall Islands and was a significant source of support for Japanese garrisons located on islands and atolls throughout the central and south Pacific. The base was the key logistical and operational hub supporting Japan's perimeter defenses in the central and south Pacific.

To ensure air and naval superiority for the upcoming invasion of Eniwetok Admiral Raymond Spruance ordered an attack on Truk. Vice Admiral Marc A. Mitscher's Task Force 58 had five fleet carriers (USS Enterprise (CV-6), USS Yorktown (CV-10), USS Essex (CV-9), USS Intrepid (CV-11), and USS Bunker Hill (CV-17)) and four light carriers (USS Belleau Wood (CVL-24), USS Cabot (CVL-28), USS Monterey (CVL-26), and USS Cowpens (CVL-25)), embarking more than 500 planes. Supporting the carriers was a large fleet of seven battleships, and numerous cruisers, destroyers, submarines, and other support ships.

Fearing that the base was becoming too vulnerable, the Japanese had relocated the aircraft carriers, battleships, and heavy cruisers of the Combined Fleet to Palau a week earlier. However, numerous smaller warships and merchant ships remained in and around the anchorage and several hundred aircraft were stationed at the atoll's airfields.



Attack
The U.S. attack involved a combination of airstrikes, surface ship actions, and submarine attacks over two days and appeared to take the Japanese completely by surprise. Several daylight, along with nighttime, airstrikes employed fighters, dive bombers, and torpedo aircraft in attacks on Japanese airfields, aircraft, shore installations, and ships in and around the Truk anchorage. A force of U.S. surface ships and submarines guarded possible exit routes from the island's anchorage to attack any Japanese ships that tried to escape from the airstrikes.

In total the attack sank three Japanese light cruisers (JAPANESE CRUISER Agano, JAPANESE CRUISER Katori, and JAPANESE CRUISER Naka), four destroyers (JAPANESE DESTROYER Oite, JAPANESE DESTROYER Fumizuki, JAPANESE DESTROYER Maikaze, and JAPANESE DESTROYER Tachikaze), three auxiliary cruisers (Akagi Maru, Aikoku Maru, Kiyosumi Maru), two submarine tenders (Heian Maru, Rio de Janeiro Maru), three other smaller warships (including submarine chasers CH-24 and Shonan Maru 15), aircraft transport Fujikawa Maru, and 32 merchant ships. Some of the ships were destroyed in the anchorage and some in the area surrounding Truk lagoon. Many of the merchant ships were loaded with reinforcements and supplies for Japanese garrisons in the central Pacific area. Very few of the troops aboard the sunken ships survived and little of their cargoes were recovered. (Lindeman, 2005)

Maikaze, along with several support ships, was sunk by U.S. surface ships while trying to escape from the Truk anchorage. The survivors of the sunken Japanese ships reportedly refused rescue efforts by the U.S. ships. The cruiser Agano, a veteran of the Raid on Rabaul and which was already en route to Japan when the attack began, was sunk by a U.S. submarine, the USS Skate (SS-305). Oite rescued 523 survivors from the Agano and returned to Truk lagoon to assist in its defense with her anti-aircraft guns. She was sunk soon after by air attack with the Agano survivors still on board, killing all of them and all but 20 of the Oite's crew.

Over 250 Japanese aircraft were destroyed, mostly on the ground. Many of the aircraft were in various states of assembly, having just arrived from Japan in disassembled form aboard cargo ships. Very few of the assembled aircraft were able to take off in response to the U.S. attack. Several Japanese aircraft that did take off were claimed destroyed by U.S. fighters or gunners on the U.S. bombers and torpedo planes.

The U.S. lost twenty-five aircraft, mainly due to the intense anti-aircraft fire from Truk's defenses. About 16 U.S. aircrew were rescued by submarine or amphibious aircraft (several Japanese, whose crew took them prisoner). A nighttime torpedo attack by a Japanese aircraft from either Rabaul or Saipan damaged the Intrepid and killed 11 of her crew, forcing her to return to Pearl Harbor and later, San Francisco for repairs. She returned to duty in June, 1944. Another Japanese air attack slightly damaged the battleship USS Iowa (BB-61) with a bomb hit.

An aerial view of the airstrike at Truk can be seen in the U.S. Navy film The Fighting Lady.

In his autobiography Baa Baa Black Sheep, U.S. Marine Corps ace pilot Gregory "Pappy" Boyington describes his experience as a prisoner of war on the ground at Truk during the raid.

Aftermath
The attacks for the most part ended Truk as a major threat to Allied operations in the central Pacific; the Japanese garrison on Eniwetok was denied any realistic hope of reinforcement and support during the invasion that began on February 18, 1944, greatly assisting U.S. forces in their conquest of that island.

The Japanese later relocated about 100 of their remaining aircraft from Rabaul to Truk. These aircraft were attacked by U.S. carrier forces in another attack on April 29–30, 1944 which destroyed most of them. The U.S. aircraft dropped 92 bombs over a 29 minute period to destroy the Japanese planes. The April 1944 strikes found no shipping in Truk lagoon and were the last major attacks on Truk during the war.

Truk was isolated by Allied (primarily U.S.) forces as they continued their advance towards Japan by invading other Pacific islands such as Guam, Saipan, Palau, and Iwo Jima. Cut off, the Japanese forces on Truk, like on other central Pacific islands, ran low on food and faced starvation before Japan surrendered in August 1945. (Stewart, 1986)

Truk IJN Anchorage Evacuation Log Book
'''Oct 31st, 1943 Truk -> Yokosuka ' BB Yamashiro''

BB Ise

CV Jun'yo

CVE Unyō

CA Tone

DD Tanikaze

DD Suzukaze

DD Umikaze

'''Nov 28th, 1943 Truk -> Yokosuka ' CVL Zuihō''

CVE Unyō

CVE Chūyō

CA Maya

DD Akebono

DD Sazanami

DD Ushio

DD Urakaze

'''Dec 1st, 1943 Truk -> Sasebo ' BB Haruna''

BB Kongō

DD Maikaze

DD Nowaki

'''Dec 7th, 1943 Truk -> Kure ' CV Zuikaku''

'''Dec 7th, 1943 Truk -> Yokosuka ' CVL Chitose''

DD Yukikaze

Food supply ship Irako

'''Dec 12th, 1943 Truk -> Yokosuka ' CV Shōkaku''

'''Jan 1st, 1944 Truk -> Yokosuka ' DD Asakaze''

Escort Manju

Cable layer Hashima

Minesweeper W-24

Yamabiko Maru

Yamakuni Maru

Keiyo Maru

'''Jan 10th, 1944 Truk -> Sasebo ' BB Yamato''

DD Michishio

DD Asagumo

DD Fujinami

'''Jan 18th, 1944 Truk -> Yokosuka ' CVL Zuihō''

CVE Unyō

DD Hatsushimo

DD Wakaba

'''Jan 19th, 1944 Truk -> Saipan ' DD Umikaze''

'''Jan 19th, 1944 Truk -> Rabaul ''' Kokuyo Maru

DD Maikaze

'''Jan 20th, 1944 Truk -> Ponape ' DD Hamanami''

Escort CH-39

Escort CH-24

Escort CH-30

Escort CH-33

Ogura Maru No. 3

'''Jan 24th Truk -> Eniwetok ' DD Suzukaze''

'''Jan 25th, 1944 Truk -> Saipan ' CVE Unyō''

DD Akebono

DD Ushio

Food supply ship Irako

'''Jan 27th Truk -> Yokosuka (convoy No. 4127) ' Escort Fukue''

Minesweeper W-23

Auxiliary subchaser Shonan Maru No. 8

Matsue Maru

Shinyo Maru

Yoshida Maru No. 3

'''Jan 28th Truk -> Rabaul ' Hikawa Maru''

'''Feb 1st, 1944 Truk -> Palau ' BB Nagato''

BB Fusō

CA Kumano

CA Suzuya

CA Tone

DD Akizuki

DD Isokaze

DD Tanikaze

DD Hamakaze

DD Urakaze

'''Feb 3rd, 1944 Rabaul -> Truk => Beppu ' Hikawa Maru''

'''Feb 3rd, 1944 Yokosuka -> Truk ' CVL Zuihō''

'''Feb 5th, 1944 Truk -> Davao ' DD Ikazuchi''

'''Feb 9th, 1944 Truk -> Saipan (convoy No. 7125) ' Escort Hirado''

Reiyo Maru

Hanagawa Maru

'''Feb 10th, 1944 Truk -> Palau ' CA Atago''

CA Chōkai

CA Haguro

CA Myōkō

DD Isokaze

DD Urakaze

DD Hamakaze

DD Tanikaze

'''Feb 10th, 1944 Truk -> Yokosuka ' BB Musashi''

CL Ōyodo

CVL Chiyoda

CVL Zuihō

DD Wakaba

DD Hatsuharu

DD Shiratsuyu

DD Michishio

DD Tamanami

'''Feb 12th, 1944 Truk -> Palau (convoy No. 7125) ' DD Hamanami''

Auxiliary subchasers Takunan Maru No. 2

Auxiliary subchasers Shonan Maru No. 5

Subchaser CH-30

Fleet oiler Sata

Tanker Hishi Maru No. 2

Ammunition ship Nichiro Maru

Cargo ship Kamikaze Maru

Cargo ship Kitakami Maru

'''Feb 13th, 1944 Truk -> Yokosuka (convoy No. 4212) ' Escort Manju''

Escort Oki

Subchaser CH-31 Fleet supply ship Irako

Fleet supply ship Tatsuura Maru

Fleet supply ship Hibi Maru

Fleet oiler Notoro

'''Feb 13th, 1944 Truk -> Kure ' CVE Kaiyo''

DD Hibiki

DD Inazuma

'''Feb 15th, 1944 Truk -> Japan ' CL Agano'', sunk 160 miles norh of Truk on Feb 16th

DD Oite, sunk while entering back Truk via North Pass with survivors from CL Agano on Feb 18th

subchaser Ch-28, sunk on Feb 16th

'''Feb 15th, 1944 ' DD Yamagumo''

DD Nowaki

Asaka Maru

'''Feb 17th, 1944 -> Truk ' DD Fujinami''

Minelayer Natsushima 

Ryuku Maru

'''Feb 17th, 1944 Truk -> Palau ' DD Shigure''

DD Harusame

'''Feb 17th, 1944 Truk -> Yokosuka ' CL Katori'', sunk

DD Maikaze, sunk

DD Nowaki, the only ship escaped

Akagi Maru, sunk

Shonan Maru #15, sunk

'''Feb 17th, 1944 Truk -> Yokosuka ' DD Nowaki''

DD Yamagumo

Asaka Maru

'''Feb 17th, 1944 Truk -> assist damaged Agano ' CL Naka'', sunk

'''Feb 18th, 1944 Truk -> Saipan ' Tenno Maru''

'''Feb 18th, 1944 Truk -> Palau ' Akitsushima''

'''Feb 20th, 1944 Truk -> Palau ' DD Fujinami''

DD Akikaze

Akashi

'''Feb 26th, 1944 Truk -> Palau ' Hikawa Maru''

'''Feb 27th, 1944 in Truk ' Subchaser CH-38'' complete battle-damage repairs

Subchaser CH-37 complete battle-damage repairs

'''Feb 29th, 1944 -> Truk ' Aratama Maru''

'''Mar 6th, 1944 Truk -> Saipan (convoy 4304) ' Subchaser CH-33''

Escort Amakusa

Escort Mikura

Minesweeper W-21

Urakami Maru

Shinane Maru

Juzan Maru

'''Mar 17th, 1944 Truk -> Saipan (convoy 4304) ' Escort Oki''

Sub tender Tsukushi Maru

Kazuura Maru

Imizu Maru

Minelayer Yurishima

'''April 27, 1944 Truk -> Palau ' Hikawa Maru''

'''May 25, 1944 Truk -> Saipan ' Ten'o Maru''

'''June 3, 1944 Truk -> Saipan ' Subchaser CH-32''

Subchaser CH-20

Subchaser CH-31

Subchaser CH-51

Escort CD-6

Auxiliary subchaser CHa-66

Moji Maru

Imizu Maru

Tatsutagawa Maru

Kojun Maru

Oiler Nitcho Maru

Oiler Kyoei Maru

Oiler Nanko Maru No. 1

13 other unidentified ships.

List of warships in Truk at the time of attack
CL Agano (阿賀野) 6,652 tons, sunk on Feb 16th, 1944

CL Naka (那珂) 5,195 tons, departed to assist CL Agano and sunk 35 mile west of Truk on Feb 17th

CL Katori (香取) 5,890 tons, sunk 40 miles northwest of Truk on Feb 17th together with Maikaze and Shonan Maru #15, only Nowaki escaped

DD Akikaze (秋風) 峯風型 1,215 tons, escaped undamaged

DD Fumizuki (文月) 睦月型 1,315 tons, anchored in repair anchorage and sunk off west of lagoon on Feb 18th despite assistance from Matsukaze and Hakachi

DD Harusame (春雨) 白露型 1,685 tons, minor damage and later escorted damaged DD Shigure from Truk to Palau

DD Maikaze (舞風) 陽炎型 2,490 tons, sunk by gunfire northwest of Truk in convoy to Yokosuka on Feb 17th

DD Matsukaze (松風) 神風型 1,400 tons, assisted and attempted to tow DD Fumizuki, medium damaged

DD Nowaki (野分) 陽炎型 2,490 tons, undamaged

DD Oite (追風) 神風型 1,270 tons, sunk while entering Truk via North Pass with survivors from CL Agano on Feb 18th

DD/P34 Susuki (薄) 樅型 935 tons, escaped but later sunk in an unrelated event off repair anchorage

DD Shigure (時雨) 白露型 1,685 tons, damaged while departing Truk via North Channel to Palau on Feb 17th

DD Tachikaze (太刀風) 峯風型 1,215 tons, ran aground on Kuop Atoll on Feb 4th and later sunk in Operation Hailstone

auxiliary cruiser Akagi Maru (赤城丸) 7,367 tons, sunk north of Truk

auxiliary submarine tender Heian Maru (平安丸) 11,616 tons, sunk off repair anchorage

aircraft transport Fujikawa Maru (富士川丸) 6,938 tons, sunk off 4th fleet anchorage

repair ship Akashi (明石) 10,500 tons, damaged

seaplane tender Akitsushima (秋津洲) 4,650 tons, damaged

Submarine chaser CH-24, 438 tons, sunk west of Truk

Submarine chaser CH-28, 438 tons, departed Truk with destroyer Oite and cruiser Agano on 15th of Feb

Submarine chaser CH-33, 438 tons, damaged

Submarine chaser CHa-20, damaged

Submarine chaser CH-29, 420 tons, sunk

auxiliary submarine chaser Shonan Maru #15 (第15昭南丸), sunk

Submarine I-10 (伊10), 2,919 tons, damaged

Submarine RO-36, 1,115 tons, damaged

Submarine RO-42, 1,115 tons, undamaged

Motor torpedo boat #10, 80 tons, sunk Cargo ship Sōya (宗谷) 3,800 tons, damaged

Target ship Hakachi (波勝) 1,641 tons, damaged

List of merchant ships at the time of attack and other shipwrecks in Truk's Anchorage
Navy transport Aikoku Maru (爱国丸) 10,348 tons, sunk off 4th fleet anchorage

Navy transport Kiyosumi Maru (清澄丸) 6,983 tons, sunk off repair anchorage

Navy transport Rio de Janeiro Maru (りおで志゛やねろ丸) 9,627 tons, sunk off 6th fleet anchorage

Navy transport Yamagiri Maru (山霧丸) 6,439 tons, carrying Yamato's 46 cm projectiles, sunk off combined fleet anchorage

Navy transport/passenger/cargo ship Kensho Maru (乾祥丸) 4,861 tons, sunk off repair anchorage

Navy transport/passenger/cargo ship Sankisan Maru (山鬼山丸) 4,776 tons, sunk off 6th fleet anchorage

Navy transport Houki Maru (伯耆丸) 7,112 ton, sunk off 4th fleet anchorage

Navy transport Reiyo Maru (麗洋丸) 5,446 tons,sunk off 4th fleet anchorage

Navy transport/freighter Syoutan Maru (松丹丸) 1,999 tons, sunk off 4th fleet anchorage

Navy water carrier/passenger/cargo ship Nippo Maru (日豊丸) 3,673 tons, sunk off 4th fleet anchorage

Navy transport Taiho Maru (大邦丸) 2,829 tons,sunk off 6th fleet anchorage

Navy transport Unkai Maru #6 (第六雲海丸), sunk off 6th fleet anchorage

Navy transport/freighter Gosei Maru (五星丸) 1,931 tons, sunk sunk off 6th fleet anchorage

Navy transport/freighter Hanakawa Maru (花川丸) 4,793 tons, sunk off Tol

Navy transport/freighter Hokuyo Maru (北洋丸) 4,217 tons, sunk off 4th fleet anchorage

Navy transport/freighter Momokawa Maru (桃川丸) 3,829 tons, sunk off 4th fleet anchorage

Navy transport/freighter San Francisco Maru (桑港丸) 5,864 tons, sunk off 4th fleet anchorage

Navy transport/freighter Unkai Maru #6(第六雲海丸) 3,188 tons, sunk off 6th fleet anchorage

Navy transport Kikukawa Maru (菊川丸) 6,853 tons, accidentally sunk on Oct 7th, 1943

Navy transport Saiko Maru (西江丸)? 5,385 tons,sunk on Feb 17th, 1944

Navy hospital ship Ten'o Maru (天應丸) 6,067 tons, anchored next to Heian Maru, escaped Navy transport Zukai Maru (瑞海丸) 2,812 tons, escaped

Navy transport Tatsuhane Maru (辰羽丸) 5,784 tons, escaped

Freighter Katsuragsan Maru (葛城山丸) 2,428 tons, sunk on Jan 4th 1944 north east off Moen

Freighter Matsutani Maru (松谷丸)? 1,999 tons

Freighter Taikichi Maru (泰吉丸)?

Freighter Hino Maru #2 (第二日野丸) 999 tons, sunk off off 6th fleet anchorage near Uman Island

Freighter Seiko Maru (星光丸)? 5,386 tons, sunk

Army transport Gyoten Maru (暁天丸) 6,865 tons, sunk by USS Tang off Truk on February 17, 1944

Army transport Yubae Maru (夕映丸) 3,200 tons,sunk off 6th fleet anchorage

Army transport/freighter Nagano Maru (長野丸) 3,810 tons, sunk off 4th fleet anchorage

Fleet oiler Shinkoku Maru (神国丸) 10,020 tons, sunk off combined fleet anchorage

Oil tanker Fujisan Maru (富士山丸) 9,524 tons, sunk south west off Moen

Auxiliary oil tanker Houyou Maru (宝洋丸) 8,691 tons, sunk off repair anchorage

Auxiliary oil tanker/passenger/cargo ship Amagisan Maru (天城山丸) 7,620 tons, sunk off 6th fleet anchorage

Auxiliary oil tanker/whaler Tonan Maru #3 (第三図南丸) 19,209 tons, sunk off repair anchorage

Auxiliary provision storeship Sapporo Maru (札幌丸), sunk on May 29, 1944 on west of lagoon

Repair ship/cargo ship Urakami Maru, anchored next to Tenno Maru and Heian Maru, damaged

Picket boat Kotohira Maru 30 tons, sunk on April 15, 1944

Salvage tug Woshima (雄島) 812 tons, accidentally sunk in an explosion with Kikukawa Maru on Oct 7th,1943

Salvage tug Futakami (二神) 600 tons, scuttled off repair anchorage postwar