Design

The twenty eight chief ship builders of Shōkaku pose at the ship's prow prior to launching (30 May 1939).

The Shōkaku class carriers were part of the same program that also included the Yamato-class battleships. No longer restricted by the provisions of the Washington Naval Treaty, which expired in December 1936, the Imperial Japanese Navy was free to incorporate all those features they deemed most desirable in an aircraft carrier, namely high speed, a long radius of action, heavy protection and a large aircraft capacity. Shōkaku was laid down at Yokosuka Dockyard on 12 December 1937, launched on 1 June 1939, and commissioned on 8 August 1941.

With an efficient modern design, a displacement of about 32,000 long tons (33,000 t), and a top speed of 34 kn (63 km/h; 39 mph), Shōkaku could carry 70–80 aircraft. Her enhanced protection compared favorably to that of contemporary Allied aircraft carriers and enabled Shōkaku to survive serious battle damage during Coral Sea and Santa Cruz.^[2]

Hull

In appearance, Shōkaku resembled an enlarged Hiryū, though with a 35.3 m (116 ft) longer overall length, 4.6 m (15 ft) wider beam and a larger island. As in Hiryū, the forecastle was raised to the level of the upper hangar deck to improve seakeeping. She also had a wider, more rounded and heavily flared bow which kept the flight deck dry in most sea conditions.^[3]

The carrier's forefoot was of the newly developed bulbous type, sometimes referred to informally as a Taylor pear, which served to reduce the hull's underwater drag within a given range of speeds, improving both the ship's speed and endurance. Unlike the larger bulbous forefoots fitted to the battleships Yamato and Musashi, however, Shōkaku's did not protrude beyond the ship's stem.^[3]

Shōkaku was 10,000 tons heavier than the Sōryū-class carriers, mainly due to the extra armor incorporated into the ship's design. Vertical protection consisted of 215 mm (8.5 in) on the main armor deck over the machinery, magazines and aviation fuel tanks while horizontal protection consisted of 215 mm (8.5 in) along the waterline belt abreast the machinery spaces reducing to 150 mm (5.9 in) outboard of the magazines^[3]

Unlike British carriers, whose aviation fuel was stored in separate cylinders or coffer-dams surrounded by seawater, all pre-war Japanese carriers had their aviation fuel tanks built integral with the ship's hull and Shōkaku was no exception. The dangers this posed, however, did not become evident until wartime experience demonstrated these were often prone to cracking and leaking as the shocks and stresses of hits or near-misses to the carrier's hull were inevitably transferred to and absorbed by the fuel tanks. Following the debacle at Midway in mid-1942, the empty air spaces around Shōkaku's aviation fuel tanks, normally pumped full of inert carbon dioxide, were instead filled with concrete in an attempt to protect them from possible damage. But this did little to prevent volatile fumes spreading to the hangar decks in the event damage did occur, particularly demonstrated when Cavalla torpedoed and sank her. Shōkaku normally stowed 150,000 gallons of AvGas for operational use.^[4]

Machinery

The geared turbines installed on Shōkaku were essentially the same as those on Sōryū, maximum power increasing by 8,000 shp (6,000 kW) to 160,000 shp (120,000 kW). In spite of all the additional armor, greater displacement and a 2.1 m (6.9 ft) increase in draught, Shōkaku was able to attain a speed of just over 34.2 kn (63.3 km/h; 39.4 mph) during trials. Maximum fuel bunkerage was 4100 tons, giving her a radius of action of 9,700 nmi (18,000 km; 11,200 mi) at 18 kn (33 km/h; 21 mph). Two same-sized downward-curving funnels on the ship's starboard side, just abaft the island, vented exhaust gases horizontally from the boilers and were sufficiently angled to keep the flight deck free of smoke in most wind conditions.^[5]

Flight Deck & Hangars

Shōkaku being launched in heavy rain at Yokosuka 1st June 1939.

Shōkaku's 242 m (794 ft) long wood-planked flight deck ended short of the ship's bow and, just barely, that of the stern. It was supported by four steel pillars forward of the hangar box and by two pillars aft.

The flight deck and both hangars (upper and lower) were serviced by three elevators, the largest being the forward one at 13 m (43 ft) by 16 m (52 ft). All three were capable of transferring aircraft weighing up to 5,000 kg (11,000 lb) and raising or lowering them took approximately 15–20 seconds.^[6]

Shōkaku's nine Type 4 electrically operated arrester wires followed the same standard arrangement as that on Hiryū, three forward and six aft. They were capable of stopping a 6,000 kg (13,000 lb) aircraft at speeds of 60–78 knots. A third crash barrier was added and a light collapsible wind-break screen was installed just forward of the island.^[3]

Hangar space was not greatly increased in comparison to the Sōryū-class carriers and both Shōkaku and Zuikaku could each carry just nine more aircraft than Sōryū, giving them a normal operating capacity of seventy-two plus room for twelve in reserve. Unlike on Sōryū, the reserve aircraft did not need to be kept in a state of disassembly, however, thereby shortening the time required to make them operational.^[7]

After experimenting with port-side islands on two previous carriers, Akagi and Hiryū, the IJN opted to build both Shōkaku and her sister-ship Zuikaku with starboard-side islands.^[3]

In September 1942, a Type 21 air-warning radar was installed on Shōkaku's island atop the central fire control director, the first such device to be fitted on any Japanese carrier. The Type 21 had a 'mattress' antenna and the initial prototypes were light enough that no major structural modifications were necessary. Later versions, however, were bulkier and required eventual removal of the fifth fire control director in order to accommodate the larger and heavier antenna.^[3]

The presence of this radar however, undoubtedly saved Shōkaku one month later at the Battle of the Santa Cruz Islands, when Shokaku was bombed by SBD-3 dive bombers from Enterprise; the early detection of the US strike planes by this radar alerted refuelling crews below deck, giving them time to drain and purge the aviation gasoline lines before they were ruptured by bomb hits, thus saving the ship from the catastrophic avgas fires/explosions that eventually caused most of the carrier sinkings in the Pacific theater.

Armament

Shōkaku's primary air defense consisted of sixteen 127 mm (5.0 in) dual-purpose AA guns in twin mountings. These were sited below flight deck level on projecting sponsons with four such paired batteries on either side of the ship's hull, two forward and two aft. Four fire control directors were installed, two on the port side and two to starboard. A fifth fire control director was located atop the carrier's island and could control any or all of the heavy-caliber guns as needed.^[3]

Initially, light AA defense was provided by twelve triple-mount 25 mm (0.98 in) AA guns. Further mounts were added in 1943.^[3]

World War II

 

Japanese aircraft carrier Shokaku 翔鶴 commencing its attack on Pearl Harbor 7th Dec 1941
Mitsubishi A6M2 "Zero" fighters (fighter division commander : Tadashi Kaneko ) from Shōkaku preparing for the attack on Pearl Harbor.

 

Pearl Harbor and subsequent operations

Service record

5th Carrier Division

Operations: World War II - Pacific War

Attack on Pearl Harbor - Indian Ocean raid of March–April 1942 - Operation Mo (the planned capture of Port Moresby in New Guinea) - Battle of the Coral Sea - Battle of the Eastern Solomons - Battle of the Santa Cruz Islands - Battle of the Philippine Sea

Shōkaku (Japanese: 翔鶴 'Flying Crane') was an aircraft carrier of the Imperial Japanese Navy, the lead ship of her class. Along with her sister ship Zuikaku, she took part in several key naval battles during the Pacific War, including the attack on Attack on Pearl Harbor, the Battle of the Coral Sea and the Battle of the Santa Cruz Islands before being torpedoed and sunk by an American submarine at the Battle of the Philippine Sea.^[1]

Operational history

Shōkaku and Zuikaku formed the Japanese 5th Carrier Division, embarking their aircraft shortly before the Pearl Harbor attack. Each carrier's aircraft complement consisted of 15 Mitsubishi A6M Zero fighters, 27 Aichi D3A1 'Val' dive bombers, and 27 Nakajima B5N1 or −2 'Kate' torpedo bombers.

Shōkaku and Zuikaku joined the Kido Butai ('Mobile Unit/Force', the Combined Fleet's main carrier battle group) and participated in Japan's early wartime naval offensives, including Pearl Harbor and the attack on Rabaul in January 1942.

Indian Ocean Raid

The Japanese inflicted disproportionate damage on the enemy. They damaged port facilities, sank one carrier and two cruisers, destroyed a third of enemy ground-based fighters and nearly all of the enemy ground-based strike aircraft. In addition, 23 merchant ships, totalling 112,312 tons, were sunk, including those by the separate Japanese Malay Force. In return, the Japanese lost only 18 aircraft (six fighters, ten dive-bombers and two high-level bombers), with damage to about 31 more. Conversely, they failed to destroy, or even locate, the main bulk of the British Eastern Fleet.

Japanese carrier naval sortie to attack British forces in East India known as Indian Ocean raid 31st Mar to 10th Apr 1942
Japanese operation in the Northern Indian Ocean and Bay of Bengal in 1942. Nagumo's forces are shown at the bottom of the map.

 

In the Indian Ocean raid of March–April 1942, aircraft from Shōkaku, along with the rest of Kido Butai, attacked Colombo, Ceylon on 5 April, sinking two ships in harbor and severely damaging support facilities. The task force also found and sank two Royal Navy heavy cruisers, (HMS Cornwall and Dorsetshire), on the same day, as well as the aircraft carrier HMS Hermes on 9 April off Batticaloa.

Battle of Coral Sea 8th May 1942

Japanese aircraft carrier Shokaku 翔鶴
Shōkaku during the Battle of the Coral Sea 8th May 1942. The Japanese aircraft carrier Shōkaku under attack by planes from USS Yorktown, during the morning of 8 May 1942. Splashes from dive bombers' near misses are visible off the ship's starboard side as she makes a sharp turn to the right.

The Fifth Carrier Division was then deployed to Truk to support Operation Mo (the planned capture of Port Moresby in New Guinea). During this operation, Shōkaku's aircraft helped sink the American aircraft carrier USS Lexington during the Battle of the Coral Sea but was herself severely damaged on 8 May 1942 by dive bombers from USS Yorktown and Lexington which scored three bomb hits: one on the carrier's port bow, one to starboard at the forward end of the flight deck and one just abaft the island. Fires broke out but were eventually contained and extinguished. The resulting damage required Shōkaku to return to Japan for major repairs.

On the journey back, the carrier shipped so much water through her damaged bow she nearly capsized in heavy seas, maintaining a high rate of speed in order to avoid a cordon of American submarines out hunting for her. She arrived at Kure on 17 May 1942 and entered drydock on 16 June 1942. Repairs were completed within ten days and, a little over two weeks later on 14 July, she was formally reassigned to Striking Force, 3rd Fleet, Carrier Division 1.^[8]

The time required for repairs, combined with the aircraft and aircrew losses incurred by her and Zuikaku, kept both carriers from participating in the Battle of Midway.

Following her return to front-line duty, both Shōkaku and her sister-ship Zuikaku, with the addition of the light carrier Zuihō, were redesignated as First Carrier Division and took part in two further battles in 1942: the Battle of the Eastern Solomons, where they damaged USS Enterprise, and the Battle of the Santa Cruz Islands, where they crippled USS Hornet (Hornet was abandoned and later sunk by Japanese destroyers Makigumo and Akigumo), but Shokaku was in turn damaged by dive-bombers of Enterprise, which therefore prevented the bombardment of nearby Henderson Field, and once again kept her out of action for months, leaving other Japanese defensive operations in the Pacific lacking sufficient airpower.

At Santa Cruz, on 26 October 1942, Shōkaku was again seriously damaged, taking at least three (and possibly as many as six) 1,000-lb. bomb hits from a group of fifteen Douglas SBD-3 dive bombers launched from Hornet. With ample warning of the incoming American strike, Shōkaku's aviation fuel mains to the flight deck and hangars had been drained down and she had few aircraft on board at the time of the attack. As a result, no major fires broke out and her seaworthiness was preserved. Her flight deck and hangars, however, were left in shambles and she was unable to conduct further air operations during the remainder of the battle.^[6][9]

Japanese fighter and dive bomber aircraft on Shōkaku prepare to launch for an attack on U.S. carrier forces

Carrier action on 26 October: first strikes

At 02:50 on 26 October, the Japanese naval forces reversed direction and the naval forces of the two adversaries closed the distance until they were only 200 nmi (370 km; 230 mi) away from each other by 05:00.[31] Both sides launched search aircraft and prepared their remaining aircraft to attack as soon as the other side's ships were located. Although a radar-equipped Catalina sighted the Japanese carriers at 03:10, the report did not reach Kinkaid until 05:12. Therefore, believing that the Japanese ships had probably changed position during the intervening two hours, he decided to withhold launching a strike force until he received more current information on the location of the Japanese ships

At 06:45, a U.S. scout aircraft sighted the carriers of Nagumo's main body. At 06:58, a Japanese scout aircraft reported the location of Hornet's task force.[34] Both sides raced to be the first to attack the other. The Japanese were first to get their strike force launched, with 64 aircraft, including 21 Aichi D3A2 dive bombers, 20 Nakajima B5N2 torpedo bombers, 21 A6M3 Zero fighters, and 2 Nakajima B5N2 contact aircraft on the way towards Hornet by 07:40.[35] This first strike was commanded by Lieutenant Commander Shigeharu Murata, while the fighter cover was led by Lieutenants Ayao Shirane and Saneyasu Hidaka. Also at 07:40, two U.S. SBD-3 Dauntless scout aircraft, responding to the earlier sighting of the Japanese carriers, arrived and dove on Zuihō. With the Japanese combat air patrol (CAP) busy chasing other U.S. scout aircraft away, the two U.S. aircraft were able to hit Zuihō with both their 500-pound bombs, causing heavy damage and preventing the carrier's flight deck from being able to land aircraft.

Meanwhile, Kondo ordered Abe's Vanguard force to race ahead to try to intercept and engage the U.S. warships. Kondo also brought his own Advanced force forward at flank speed so that Jun'yō's aircraft could join in the attacks on the U.S. ships. At 08:10, Shōkaku launched a second wave of strike aircraft, consisting of 19 dive bombers and five Zeros, and Zuikaku launched 16 torpedo bombers and 4 Zeros at 08:40. The second strike leader was Lieutenant Commander Mamoru Seki, while the fighter cover was led by Lieutenant Hideki Shingo. Thus, by 09:10 the Japanese had over 100 aircraft on the way to attack the U.S. carriers.

The U.S. strike aircraft were running about 20 minutes behind the Japanese. Believing that a speedy attack was more important than a massed attack, and because they lacked fuel to spend time assembling prior to the strike, the U.S. aircraft proceeded in small groups towards the Japanese ships, rather than forming into a single large strike force. The first group—consisting of 15 Douglas SBD Dauntless dive bombers, 6 Grumman TBF-1 Avenger torpedo bombers, and eight Grumman F4F Wildcat fighters, led by Lieutenant Commander William J. "Gus" Widhelm from Hornet—was on its way by about 08:00. A second group—consisting of three SBDs, nine TBFs (including the Air Group Commander's), and eight Wildcats from Enterprise, led by Lieutenant Commander John A. Collett—was off by 08:10. A third group—consisting of nine SBDs, ten TBFs (including the Air Group Commander's), and seven F4Fs from Hornet—was on its way by 08:20.

At 08:40, the opposing aircraft strike formations passed within sight of each other. Lieutenant Hidaka's nine Zuihō Zeros surprised and attacked the Enterprise group, attacking the climbing aircraft from out of the sun. In the resulting engagement, four Zeros, three Wildcats, and two TBFs, including Collett's, were shot down, with another two TBFs and a Wildcat forced to return to Enterprise with heavy damage.[38] The remaining Zuihō Zeros, having exhausted their ammunition, withdrew from the action.

Shōkaku crew members fight fires on the flight deck after being hit by American bombs during the Battle of the Santa Cruz Islands

At 08:50, the lead U.S. attack formation from Hornet spotted four ships from Abe's Vanguard force. Pressing on, the U.S. aircraft sighted the Japanese carriers and prepared to attack. Three Zeros from Zuihō attacked the formation's Wildcats, drawing them away from the bombers they were assigned to protect. Thus, the dive bombers in the first group initiated their attacks without fighter escort. Twelve Zeros from the Japanese carrier CAP attacked the SBD formation, shot down two (including Widhelm's, though he survived), and forced two more to abort. The remaining 11 SBDs commenced their attack dives on Shōkaku at 09:27, hitting her with three to six bombs, wrecking her flight deck, and causing serious damage to the interior of the ship. The final SBD of the 11 lost track of Shōkaku and instead dropped its bomb near the Japanese destroyer Teruzuki, causing minor damage. The six TBFs in the first strike force, having become separated from their strike group, did not find the Japanese carriers and eventually turned back towards Hornet. On the way back, they attacked the Japanese heavy cruiser Tone, missing with all their torpedoes.

Chikuma under attack on 26 October. Smoke emerges from the center of the ship where a 1,000 lb (450 kg) bomb hit directly on the bridge

The TBFs of the second U.S. attack formation from Enterprise were unable to locate the Japanese carriers and instead attacked the Japanese heavy cruiser Suzuya from Abe's Vanguard force but caused no damage. At about the same time, nine SBDs from the third U.S. attack formation—from Hornet—found Abe's ships and attacked the Japanese heavy cruiser Chikuma, hitting her with two 1,000 lb (450 kg) bombs and causing heavy damage. The three Enterprise SBDs then arrived and also attacked Chikuma, causing more damage with one bomb hit and two near-misses. Finally, the nine TBFs from the third strike group arrived and attacked the smoking Chikuma, scoring one more bomb hit. Chikuma, escorted by two destroyers, withdrew from the battle and headed towards Truk for repairs.

Aichi D3A type 99 or Val EI-306 from the Japanese carrier Soryu shot down Battle of Coral Sea

The U.S. carrier forces received word from their outbound strike aircraft at 08:30 that Japanese attack aircraft were headed their way.[42] At 08:52, the Japanese strike force commander sighted the Hornet task force—the Enterprise task force was hidden by a rain squall—and deployed his aircraft for attack. At 08:55, the U.S. carriers detected the approaching Japanese aircraft on radar—about 35 nmi (65 km; 40 mi) away—and began to vector the 37 Wildcats of their CAP to engage the incoming Japanese aircraft. However, communication problems, mistakes by the U.S. fighter control directors, and primitive control procedures prevented all but a few of the Wildcats from engaging the Japanese aircraft before they began their attacks on Hornet.[43] Although the U.S. CAP, including fighter pilot Swede Vejtasa, was able to shoot down or damage several dive bombers (the formation leader Lieutenant Sadamu Takahashi had to abort the dive due to the damage[44]), most of the Japanese aircraft commenced their attacks relatively unmolested by U.S. fighters.

A damaged Japanese dive bomber (upper left) dives towards Hornet at 09:14 ...... and seconds later crashes into the carrier.

At 09:09, the anti-aircraft guns of Hornet and her escorting warships opened fire as the 20 untouched Japanese torpedo planes and remaining 16 dive bombers commenced their attacks on the carrier.[46] At 09:12, a dive bomber placed its 250 kg semi-armor-piercing "ordinary" bomb dead center on Hornet's flight deck, across from the island, which penetrated three decks before exploding, killing 60 men. Moments later, a 242 kg high-explosive "land" bomb struck the flight deck, detonating on impact to create an 11 ft (3.4 m) hole and kill 30 men. A minute or so later, a third bomb hit Hornet near where the first bomb hit, penetrating three decks before exploding, causing severe damage but no loss of life. At 09:14, a dive bomber was set on fire by Hornet's anti-aircraft guns; the pilot, Warrant Officer Shigeyuki Sato, deliberately crashed into Hornet's stack, killing seven men and spreading burning aviation fuel over the signal deck.

At the same time as the dive bombers were attacking, the 20 torpedo bombers were also approaching Hornet from two different directions. Despite suffering heavy losses from anti-aircraft fire, including Murata, the torpedo planes planted two torpedoes in Hornet's side between 09:13 and 09:17, knocking out her engines. As Hornet came to a stop, a damaged Japanese dive bomber approached and purposely crashed into the carrier's side, starting a fire near the ship's main supply of aviation fuel. At 09:20, the surviving Japanese aircraft departed, leaving Hornet dead in the water and burning.[49] Twenty-five Japanese and six American aircraft were destroyed in this attack, including 12 dive bombers, ten torpedo planes and at least one Zero.

With the assistance of fire hoses from three escorting destroyers, the fires on Hornet were under control by 10:00. Wounded personnel were evacuated from the carrier, and an attempt was made by the heavy cruiser USS Northampton under Captain Willard A. Kitts to tow Hornet away from the battle area. However, the effort to rig the towline took some time, and more attack waves of Japanese aircraft were inbound.

After several months of repairs and training, Shōkaku, now under the command of Captain Matsubara Hiroshi, was assigned in May 1943 to a counterattack against the Aleutian Islands, but the operation was cancelled after the Allied victory at Attu. For the rest of 1943, she was based at Truk, then returned to Japan for maintenance late in the year.

 

Sinking

In 1944, Shōkaku was deployed to the Lingga Islands south of Singapore. On 15 June, she departed with the Mobile Fleet for Operation 'A-Go', a counterattack against Allied forces in the Mariana Islands. Her strike waves suffered heavy losses from US Combat Air Patrols and anti-aircraft fire, but some survived and returned safely to the carrier. One of her D4Y Suisei strike groups, composed of veterans from the Coral Sea and Santa Cruz engagements, broke through and one plane allegedly struck home with a bomb that damaged USS South Dakota (BB-57) and caused many casualties, but this group suffered heavy losses themselves. During the Battle of the Philippine Sea, she was struck at 11:22 on 19 June by three (possibly four) torpedoes from the submarine USS Cavalla (Commander Herman J. Kossler).

As Shōkaku had been in the process of refueling and rearming aircraft and was in an extremely vulnerable position, the torpedoes started fires that proved impossible to control. At 12:10, an aerial bomb exploded, detonating aviation fuel vapors which had spread throughout the ship. 'Abandon Ship' was ordered, but before the evacuation had progressed very far, Shōkaku abruptly took on water forward and sank quickly bow-first at position 11°40′N 137°40′E, taking 1,272 men with her. The light cruiser Yahagi and destroyers Urakaze, Wakatsuki, and Hatsuzuki rescued Captain Matsubara and 570 men.^[1]

The Sinking of Shokaku -- An Analysis

By Anthony Tully, Jon Parshall and Richard Wolff
Web Reference: http://www.combinedfleet.com/shoksink.htm

In the Battle of the Philippine Sea (called the Battle for the Marianas by the Japanese), the Imperial Japanese Navy lost three aircraft carriers within a period of thirty-six hours. These were the Taiho, Shokaku, and Hiyo. All three were victims of the same fateful combination of torpedo damage that set up massive vapor-induced explosions. Adequate reports exist for the Taiho and, to a lesser degree, for the Hiyo's loss. This analysis concerns itself with the third carrier mentioned, the veteran and famous Shokaku, torpedoed and sunk by U.S.S. Cavalla (SS-244) on 19 June 1944.

The Shokaku was indeed a famous ship, and battle-scarred as well. Her illustrious record included such battles as the attack on Pearl Harbor, the Indian Ocean sorties, the Battle of Coral Sea, and the naval battles around Guadalcanal. With sister-ship Zuikaku as part of CarDiv 5, the Shokaku had participated in nearly every carrier battle except Midway. Indeed, some historians cite the absence of the Shokaku and Zuikaku -- recovering from Coral Sea damage or losses -- as the deciding factor in the Japanese defeat at Midway. Whether that is true or not, there was no denying that Shokaku's record and crew were both of the highest standing. It was natural, then, that she and her sister should be teamed with the grand new carrier Taiho when Admiral Ozawa set forth to challenge the U.S. invasion of Saipan in June 1944.

It was widely hoped that the unprecedented combination of Imperial sea and land-based air forces would turn the tide at the Battle of the Philippine Sea, but it was not to be. Taiho would perish from complications arising from a single torpedo hit, and Shokaku herself would be sunk this selfsame day by the same agent -- U.S. submarines. Yet that sinking is veiled by a remarkable reticence of detail -- a frustrating brevity of story that forms an unsatisfactory end to such a brilliant career.

The reason is that the bulk of the Shokaku's Detailed Action Report for this battle has apparently been lost or destroyed. This action report, or DAR, would have given details of the damage, damage control measures taken, and the chronology of the crew's gallant but losing battle to save the ship. This section, however, has been lost and no detailed accounts from modern Japanese authors have been encountered or translated to date, though they surely must exist. Instead, the historian is left with a few brief summaries: two short paragraphs in the NavTech Report and a couple of almost passing references in "The Campaigns of the Pacific War". These form the kernel of what is known from the Japanese side about the sinking. The following is an amalgam of the short remarks contained in NavTechJap Article S-06-3 dated January 1946:

"Shokaku (CV-6) - Shokaku Class. Sunk 19 June 1944 during the Battle of the Philippine Sea. 1100 (approx.) She was west of the Marianas when struck by not more than three submarine torpedoes. One was close to the forward bomb magazines. Gasoline tanks were ruptured, and there was a fire of undetermined proportions. The fire was extinguished promptly, according to survivors, by closing all access to the spaces surrounding the gasoline tanks. Gasoline fumes, however, began to seep throughout the ship. Several hours later an enormous explosion caused her to disintegrate. It may have been her bomb magazines."

While the preceeding reference may have been influenced by the American point of view, "The Campaigns of the Pacific War" includes faithful translations of Japanese source documents. But except for track position coordinates that conflict from one report to another, the only added information is a repeated assertion that Shokaku was hit by four torpedoes. This presents a definite discrepency between American accounts and the meager surviving details from the Japanese point of view.

In 1952, less than ten years after these reports were written, Fukaya Hajime wrote an article on the Shokaku-class vessels for U.S. Naval Institute Proceedings. Though his account of the sinking is brief, it adds a remarkable additional detail as given from the Japanese side. Fukaya writes that, after the torpedoes hit Shokaku, "damage to the carrier, already severe, was compounded by the outbreak of fires which soon enveloped the entire ship. The situation soon became hopeless as the ship settled rapidly by the bow. Water quickly reached the flight deck and spilled through the open Number 1 elevator into the hanger. Thus stricken the Shokaku lost stability, turned over, and sank".

With the exception of a few other scant notes, these three sources form the core of nearly every account of the Shokaku's sinking published in English to date, from Normal Polmar's brilliant "Aircraft Carriers" and John Toland's "Rising Sun" to the more modern "Red Sun Setting" of W.T. Youngblood. Though modern Japanese sources or memoirs were hoped to exist, the primary source quotes above represented the sum total discovered by the authors prior to this analysis of Shokaku's loss. Such sparseness of detail, for so great a ship, seemed a gap in the historical record. Since the action capsule did give one vital clue regarding the location of one of the torpedo hits, the authors were challenged to seize upon that fact to reconstruct the sinking mathematically, as has been done with such noted success recently with RMS Titanic.

Though such a reconstruction could only be speculation, the temptation to try was spurred by the fact that - in contrast to the IJN records - the U.S. side was amply covered. Cavalla's full attack report includes the firing angles and sequences of the torpedoes launched. Armed with this, we resolved to match the Cavalla's attack figures to the one fixed point - the hit near the for'd bomb magazines - and proceed from there, bearing in mind the historical conditions that had to be satisfied. What began as an analytical exercise evolved into the present article when a modern Japanese source account was found, and contributed important and unique details. Given their value, it was decided to publish the study. The analysis that follows, while necessarily speculative, did exhibit striking correlation to the new information discovered. The work is in two parts: (A) The reconstruction analysis, and (B) the historical narrative. Although the analysis itself cannot be asserted as factual, since the sources remain reticent on the question of the impact points, it seemed useful to present it here.

Circumstances of the Attack

At 1100 19 June 1944 the three crack carriers Taiho, Zuikaku, and Shokaku were steaming proudly in formation, having launched air strikes against the U.S. carrier fleet covering the invasion of the Marianas. The trio formed a spearhead, with Zuikaku in the lead, and the Taiho and Shokaku on the port and starboard quarters of the formation respectively. This was the titanic Battle of the Philippine Sea, and at an hour before noon that day the Japanese carrier fleet had not even been found by search planes, and had already launched two strikes against their foe. The portents could hardly have been more favorable. Yet within five hours, two of these carriers would be demolished and the scales of battle irrevocably tipped against the Japanese.

It had begun at 0810, when the USS Albacore had slammed a fateful single torpedo hit into Ozawa's proud flagship, Taiho. The Taiho had shrugged off the damage, but fumes were gathering below decks that would eventually reach a fatal concentration. Meanwhile, nearly three hours after this strike, a second U.S. submarine struck. She was the USS Cavalla. She had come in on the southern flank of the Japanese fleet and at 1048 had sighted the Shokaku in the process of landing a recon patrol.

Excitedly the Cavalla's skipper, Lt. Comdr. Herman Kossler, had watched as the big Japanese carrier steamed a steady course into the southeast wind, raising large bow waves. The destroyer Urakaze steamed languidly alongside to starboard, seemingly oblivious to the submarine's presence, while two cruisers (identified by Cavalla at the time as Atago-class) were ahead off the carrier's port bow. (Actually this was light cruiser Yahagi and probably heavy cruiser Haguro.) It was nearly a perfect setup. At 1118, after only having to raise periscope three times, and at a range of 1,200 yards the Cavalla unleashed a salvo of six torpedoes at the Shokaku's starboard side . . .

Modeling the Attack on Shokaku

Cavalla's log gives us three crucial pieces of data with which to reconstruct the attack:

First, it details exactly the bearings of all six torpedoes fired, and their firing sequence.
Second, it details Cavalla's and Shokaku's course and speed.
Third, it provides fairly exact timings of torpedo impacts against Shokaku.

Given these clues, we went about filling in the details of the torpedo attack and the likely impact points of the torpedoes against Shokaku. The geometry of Cavalla's torpedo spread was known, and could be reconstructed fairly exactly. To do so, a mathematical model of the engagement was built which accounted for:

A rather complex torpedo launch sequence, wherein the torpedo is being launched at a slower speed, accelerating, and turning to the correct bearing, all within the first six to eight seconds after launch.
Cavalla's motion through the water

Target motion

In this way, it was possible to put together a detailed picture of Cavalla's spread that depicted the torpedoes positions on a second-by-second basis. (The assumptions behind this depiction are noted in the footnotes section.)

Once the geometry of the torpedo spread was created, the next step was to reconstruct the motion of Shokaku. This was trickier to do, since we knew very little about her relative position and movements other than her course and speed. The only way to solve this dilemma was to place Shokaku's position relative to a torpedo that hit her, and then work from there. We know she was hit by torpedo #1 at T=50 seconds. Furthermore, Cavalla's log claims that probably the first three torpedoes hit Shokaku, with hits occurring at 8 second intervals. Lastly, Japanese accounts indicate that at least one torpedo struck in the forward aviation gasoline storage tanks.

With that knowledge, we set about creating three separate scenarios in which the Shokaku's aviation gas storage gets hit by either torpedo #1, #2, or #3. By placing Shokaku relative to a torpedo striking the forward avgas and then "moving" the ship mathematically backwards and forwards along her course track at the proper speed and bearing, it was possible to determine which of the other torpedoes hit or missed in each specific scenario. A graphical example of the outcome of this method is shown below:

The results of this approach were intriguing, to say the least, and we discuss each of the three resulting hit scenarios below.

In scenario #1, it is assumed that it is torpedo #1 that strikes Shokaku's avgas, at T=50 seconds. This scenario also produces a hit by torpedo #2 at T=57 seconds which impacts Shokaku almost directly on the bulkhead dividing Boiler Rooms #3 and #5. Torpedo #3 then hits at the forward end of the bridge. Torpedo #4 misses astern by about 130 feet. Torpedo #5 hits some 60 feet behind the bow. Torpedo #6 misses astern by nearly 300 feet.

Analysis: This scenario produces four hits in the forward half of the ship, and causes heavy flooding. Torpedo #1 causes the requisite damage to the avgas storage and starts fires. Torpedo #2 would most likely flood two of Shokaku's eight boiler rooms, and might stop Shokaku's machinery as well (there are several instances of large Japanese warships having their propulsion systems incapacitated by a single torpedo hit). Torpedo #3 hits on or near the forward magazines and torpedo storage area, and likely contributes to the damage already sustained near the avgas storage. After this third hit, Shokaku may have had as much as one hundred sixty feet of her starboard length flooded, including a number of large machinery spaces. This would have undoubtedly caused a starboard list. In the midst of this chaos, Torpedo #5 then hits home well forward, possibly blowing a hole through both sides of the bow (which is no more than 15-20 feet in breadth in this region. This hit would cause still more flooding and would contribute to the bow trim (mentioned in some Japanese sources) by virtue of the relatively larger flooding moment that such a hit in the extremities would produce. The overall damage profile is one of extensive flooding forward, serious fires, an imminent danger to the forward magazines themselves, and heavy damage to the boiler rooms.

In scenario #2, torpedo #2 is presumed to strike the avgas at T=57 seconds. By backtracking to T=50, we find that torpedo #1 hits the extreme end of the bow. Torpedo #3 hits about 60 feet further aft of Torpedo #1. Torpedo #4 hits almost directly on the rudder. Torpedo #5 misses ahead by more than 130 feet. Torpedo #6 misses astern by about 90 feet.

Analysis: Scenario #2 produces a damage profile which puts three hits in the bow of the ship, and one hit in the stern. The two bow hits at the extreme stem would likely produce the bow trim mentioned in the Japanese record. The hit in the avgas (by default) produces fires. However, the hit in the rudder area is not mentioned in any of the Japanese accounts. The failure to note a hit in this region is extremely unlikely, given both the critical nature of this space to the ship's operations, and the large separation between it and the hits forward (which would have made it even more noticeable).

Scenario #3 produces three hits against the ship. Torpedo #1 strikes forward, near the rearmost bow trim tank. Torpedo #2 hits Boiler Room #1 directly. Torpedo #3 hits the avgas. Torpedo #4 misses astern by about 70 feet. Torpedo #5 just barely misses the bow by a matter of a few feet, (although the overhang of the stem makes this distance even larger and almost ensures a miss). Torpedo #6 misses astern by more than 200 feet.

Analysis: This third scenario produces a damage profile similar, but not as severe, as Scenario #1. A bow trim is again likely as a result of the damage, and some machinery damage is in evidence as well, with Boiler Room #1 being flooded and damage to the forward generator (which was just forward of the forward pair of boiler rooms) likely. The hit in the extreme bow contributes to the bow trim.

We then examined the three scenarios for a best fit with the historical data. In order to satisfy the record, a good scenario should fulfill the following criteria:

1] Does it fracture the av-gas tank
2] Does it likely cause a bow-heavy trim and steady settling to develop
3] Does it inflict sufficient machinery damage to stop the carrier
4] Does it seem to account for an immediate loss of electrical power
5] Does it support a #1-#2-#3 torpedo hit pattern as reported by Cavalla
6] Does it start fires
7] Does it give four hits rather than just three, as the Japanese tend to believe

The results matrix for the scenarios is presented below:

Scenarios/Criteria One Two Three
Avgas Hit Yes (by default) Yes (by default) Yes (by default)
Causes Bow Trim Yes Yes Yes
Machinery Damage Yes No Maybe
Loss of Electrical Power Maybe No Probably
#1-#2-#3 Hits Yes Yes Yes
Starts Fires Yes (by default) Yes (by default) Yes (by default)
4 Hits Total Yes Yes No

Scenario Analysis

Beyond the matrix presented above, each of the scenarios has its strengths and (in some cases) weaknesses. Scenario #2 is clearly the weakest of the three, as it is hampered by its inclusion of a hit on the rudder, which is at odds with the historical record by its omission. It also produces no direct damage to the machinery of the ship. The fact that Shokaku ground to a halt relatively close by Cavalla is a clear indication that her machinery was rendered inoperable relatively quickly. The fastest way to accomplish this is through direct damage to either the boilers or the engine rooms, neither of which is supported by this scenario.

Scenario #3, while matching the letter of the base criteria, begins to look less promising on closer inspection. It produces only three hits, and an examination of the hits reveals that only #3 (the hit in the avgas) can really be considered serious, although the hit on the forward boiler room could be more serious if it also damaged the generator spaces immediately forward (which is a distinct possibility). However, the overall impression one gets is of a ship that is only moderately damaged. The Japanese record suggests a far more devastating set of circumstances.

Scenario #1 produces just such a situation. The four hits are spaced all along the bow and manage to hit just about everything of value there, including the avgas, magazines, and machinery spaces. Torpedo #3, in particular, strikes a particularly vital point in the carrier and acts as a damage multiplier for torpedoes #1 and #2 because it threatens both machinery (in this case the electrical generating equipment immediately forward of the boiler rooms) as well as the avgas and magazines. This hit would likely complicate damage control efforts in both of the earlier hit locales. Not only that, but many of the spaces hit under this scenario (boiler rooms and magazines) are relatively large (and tall), meaning that flooding would be more severe and produce larger potential lists. As a result, Shokaku probably loses two boiler rooms instantly, and has further fires burning forward of the engine spaces. The final hit in the bow is well placed to destroy the navigability of the vessel and also exacerbate the bow trim by virtue of its placement on the extreme end of the ship. The net result is a damage profile of unusual severity.

An additional point in the historic record also supports this scenario. One Japanese source mentions specifically that the initial hit sent a combination of water and burning substances in a spray across the front of the bridge, killing several aviators there. This description strongly indicates that it was the initial hit that impacted the aviation gasoline stores. All in all, in the authors' estimation, this scenario fits the historical record almost perfectly.

Error Analysis

Our analysis was subject to a number of sources of potential error. We discuss these sources, and their likely impact below.

The course tracks for Cavalla, Shokaku, and the torpedoes may be in error. This is a possibility; however, Cavalla's logs seem fairly detailed with regards to obtaining an accurate course and speed for the target. In order to produce a valid target solution, Cavalla had to generate accurate course tracks for Shokaku. The nature of this attack seems to be an orderly one - Cavalla was able to launch a well thought-out spread at the target, rather than simply loosing a volley in desperation as she dove deep.

The timing of the initial hit on Cavalla at T=50 seconds may be in error. At the speed the torpedo spread was travelling, and given the angles of the spread, any discrepancy here would necessarily introduce a large error in the impact points of the torpedoes. Our response to this mainly rests on the timing of the impacts produced by the mathematical model we built. In this model, when we fed course data of the two ships, as well as firing data, we got back impact times which match the 8-second separation of the historical record very closely (within a second).

The torpedoes may not run true, or may run faster or slower than rated. After discussing this possibility with Dr. Frederick Milford, a noted expert on WWII torpedo technology, we discounted this risk factor. By this point in the war, American torpedoes had generally worked out the teething problems that had plagued them earlier in the war. Dr. Milford's opinion was that the torpedoes would most likely "perform as advertised", and would therefore strike very close to their predicted impact points. The Mk 23 torpedo's "wander" (the amount of lateral inaccuracy over the range traveled) at a range of 1,200-1,500 yards would most likely be a matter of a few feet, not yards.

The forward aviation gasoline storage area itself is a fairly large target, leading to corresponding uncertainty as to the precise point of impact in this area. This, in turn, affects the accuracy of the other hits as well. Shokaku's forward aviation fuel tanks cover approximately 40 feet of her length. A hit anywhere in this region, or even fairly near it, would produce the fires mentioned in the historical record. As a result, an error of plus or minus 25 feet is probably not a bad margin of error to apply to the predicted hit locations of the other torpedoes as well. Obviously, this has potentially important implications. To try and make this potential source of inaccuracy more apparent, we have intentionally chosen to size our "torpedo hit" icons such that they take up an area roughly equal to this margin of error.

Shokaku's starboard evasive maneuver, while insufficient to avoid the first three torpedoes, may have caused later torpedoes to miss. Furthermore, if Shokaku's machinery was damaged immediately by the initial hits, she may have slowed enough to cause later torpedoes to miss ahead. This applies mostly to Scenarios #1 and #2, which predict Shokaku taking hits in the extreme bow. In the authors' opinions, the possibility that later hits may have been affected by Shokaku's maneuvers cannot be discounted. However, it also cannot be modeled with any degree of accuracy. Given the relative 'cleaness' of the model we had managed to build, we decided not to tamper with it on the basis of the very speculative evidence at hand regarding Shokaku's despairing efforts at evasion. The turning and/or slowing of the ship does potentially produce one fewer hits on the ship, if it actually occurred. Without better evidence that it did occurr, we chose not to modify the fundamentals of the model.

The Damage

(Shokaku sinking, from John Hamilton's "War at Sea.")

In the foregoing analysis we attempted to locate the likely impact points as indicated by the best evidence, but bear in mind the results must be regarded as hypothetical. However, the description of the aftermath and sinking that follows belongs to the realm of reported fact, and relates details of Shokaku's last hours beleived to be previously unpublished in English.

At 1120 the Shokaku's watch was preoccupied scanning the skies for enemy aircraft, and were later judged to not have been as mindful of danger from below as they should have been. Thus when the lookout sighted torpedoes bearing 60 degrees off the starboard bow and gave warning, the tracks were already very close and it was too late. Though Captain Matsubara ordered evasive action, the situation was beyond redemption. Three, possibly four, torpedoes (survivors disagree) struck the ship at eight second intervals. The torpedo hits, whether three or four, were devastating, but not immediately fatal.

Hits were recorded concentrated on the starboard side forward and amidships. One torpedo hit under and forward of the island, shattering and igniting an av-gas main that sent a fireball and burning spray bursting upwards in front of the bridge, burning and injuring several aviators relaxing before the island. Immediately some of the just-landed and fueling aircraft in the hangar exploded into flames, and the pressure of the detonation lifted the elevators 90 centimeters (nearly three feet). The wrecked lifts fell back into the wells, dumping hapless mechanics who had been standing on the forward lift into the inferno.

Shokaku had just recovered planes and was fueling others when the torpedoes struck; thus highly volatile av-gas was flowing through pipes in the vicinity of the impacts. Nothing could have been as catastrophic in timing. As many as nine aircraft were in the hangar, and the hangar was turned into chaos by the shocks. Gas spewed from ruptured aircraft tanks and caught fire, and ammunition on hoists began to explode, turning the hangar into a blast furnace. Exploding bombs and aircraft fuel tanks added to the conflagration and cut down men trying to fight the fire, so that pieces of "dismembered bodies lay everywhere about the deck".

With boiler rooms on the starboard side flooding quickly, the Shokaku at once lost speed, fell out of formation, and began to list rapidly to starboard. Reacting quickly, Captain Matsubara ordered port spaces counterflooded to correct the list. This was done, but too well, as damage control efforts overcompensated, and Shokaku flopped over into an opposite heel to port! (It should be noted that the magnitude of counterflooding necessary to accomplish this reverse heel to port most likely would have involved flooding of port-side machinery spaces, further complicating Shokaku's power situation.) At the same time the carrier was beginning to trim noticeably by the bow, for one of the torpedoes there had opened a large hole. 9Our analysis revealed just such a hit and raised the distinct possibility that the bow was rent clean through, which could explain the marked head trim reported throughout). The upshot was that before noon the Shokaku had become unnavigable and gone dead in the water, fires raging.

In the interim, the fire in the hangar had become an inferno, for all electric circuits had failed immediately following the hits. One of the torpedoes had struck close to the forward bomb magazines and apparently this had knocked out the generator and switchboard located in this very area. (Once again, the historical record gives striking confirmation of our reconstruction, which shows just such a hit). When power failed it was impossible to power the pumps. The blaze made it impossible to reach or man the armored control booths for the fire mains in the hangar and thus there was no effective means to contain the mounting conflagration. In desperation the veteran damage control teams broke out portable extinguishers and even formed bucket brigades. However, such measures could hardly prevail against the flames, and the burning gasoline spewing from shattered pipes that "came down like burning rain on their heads". The ship was in extreme jeopardy.

Nonetheless, Shokaku's damage control was among the most experienced in Kido Butai, experience born of hard-trials, when they had saved Shokaku twice---first at the Battle of the Coral Sea, and then at Santa Cruz. Those lessons now came into play and by early afternoon there seemed cause for hope. Though the fire in the hangar still raged, those in the gas tanks had been extinguished by closing off all access in the surrounding spaces. There were not too many aircraft aboard, and there was a chance the fuel fires in the hangars could be doused if they could just be contained. The inadvertent list to port remained moderate, and helped balance the rising water in the starboard side. However, the pumps were not operable and the bow continued to settle. If power could be restored, there might be hope, but this seemed unlikely. Not only that, but the deadly and highly flammable vapor from the unrefined Tarakan fuel oil (now being widely used in extremis aboard Japanese warships as Japanese refineries had run dry due to shipping losses) and the ruptured gas tanks had begun to spread through the ship. The enclosed hangar had poor ventilation in the best of conditions, and many of the ventilators were now destroyed. Thus, even though damage control had made progress in isolating the main outbreaks of fire to forward and amidships, their efforts were nullified as leaking gas and ammunition periodically exploded.

In the meantime, the Shokaku's attacker had been weathering a rather ferocious depth charge attack from Lt. Comdr. Yokota Yasuteru's Urakaze. The first salvo of four exploded at the same time as Kossler's fourth torpedo, close and to port of the sub. Subsequently over the next three hours, the Cavalla counted 106 depth charges, 56 of which "were fairly close". The shocks started flooding in the hull induction and ventilation supply piping outboard, the QB and JK-C supersonice gear burned out, and all sound but JP disabled. But this damage was moderate, and by 1330 the depth charges began to slacken. Moreover, JP sound gear began to report "loud water noises" from the target. Evidently something was happening to the carrier. Indeed it was.

By 1330 the fires on Shokaku were growing much worse and flames began spouting from the flight deck and elevator wells and could be seen from the other ships. Moreover, the bow continued to subside into the sea, and the situation soon became hopeless as the forecastle came awash. Reluctantly Captain Matsubara bowed to the inevitable and gave word that all hands should come up on deck, and prepare to abandon ship. Thorough check was to be made that no one remained below to perish. Officers groped their way through burning and smoke-filled compartments, calling out names and looking for any one left behind. Several hundreds of the ship's company now gathered on the flight deck aft, where the fire had not yet reached, and assembled for roll call. Others energetically threw wreckage and rafts overboard to men who had been blown into the water, or leaped into the sea and swam to the floats themselves.

On the flight deck aft, the men waited in supernatural calm as the chiefs and officers made their head count, even though explosions continued to rock the ship and the flight deck was now starting to slant perceptibly downwards. In fact, at that very moment the seas were swallowing the forecastle and rising up to the level of the flight deck itself. As the bow settled, wreckage and bombs and burning planes in the hangar began to slide and bump forward. It was then that total catastrophe, even greater than that already in progress, struck.

Either it was touched off by one of the fires, or was set off by tumbling as the ship nosed forward, but at 1408 an aerial bomb on the hangar deck forward exploded. Immediately the volatile gases that had been accumulating below were ignited, and the Shokaku was rent by an ominous grumble deep down inside. This was followed by a truly devastating cacophony of "four terrific explosions" followed by several smaller ones as the forward bomb and torpedo magazines were touched off. In a prolonged convulsion of three minutes the Shokaku literally began to blow apart at the seams.

The men gathered aft were caught completely off-guard--they had assumed they had several minutes to evacuate; in reality they now had only seconds. They were sent tumbling and sliding down the flight deck as Shokaku's shattered bow plunged under the waves. Water surged over and across the flight deck and poured in a torrent through the open No.1 elevator into the hangar. The inrush yanked the stricken carrier downward, causing her fantail to rear terrifyingly and suddenly into the sky.

Screaming and frantically trying to grab anything to hold onto, the mass of humanity on Shokaku's flight deck aft slid down the incline to their deaths and a "fiery hell" as they fell headlong into the open and blazing No.3 elevator into the cavernous inferno that had been the hangar. Survivors already in the water were horrified and the sight of the white-clad mass streaming down to incineration in the elevator pit would remain with them for the rest of their lives. The blazing carrier's stern continued to rise, till it was nearly vertical, and in a scene reminiscent of the sinking of the Titanic, then corkscrewed downwards with a "groaning roar" and collapsed into the deep, disappearing amid churning seas, fire and smoke. Bobbing among the wreckage littered waters the scattered patches of survivors began "to sing Shokaku's song with blood tears". The time was scarcely twelve past two----only two minutes had elapsed since the induced explosion. (Position: 1200' N, 13746' E)

The stunned Yahagi and Urakaze wasted little time in dashing forward among the mass of wreckage to the rescue. The sea was fairly calm, but the suddenness of the catastrophe precluded most chances for escape. The loss of life was appalling: fully 887 petty officers and men, and 376 men of Air Group 601; a total of 1,263 souls in all, had perished. Among the dead were some of the last of Kido Butai's great veterans, including Shokaku's Air Officer, Mitsueo Matsuda, the man who had led the bombing raids that subdued Wake Island. The death toll was keenly felt, for it was the worst to date for Kido Butai, having surpassed even the much-mourned loss of Kaga at Midway. However, by some miracle Captain Matsubara Hiroshi was among the 570 fortunate survivors rescued by light cruiser Yahagi and destroyer Urakaze. As the rescuers worked, small squalls gathered about, as if "adding their tears". In contrast to the human, the aircraft toll was small---only nine planes were listed by Mobile Fleet as having gone down with Shokaku. With the sinking of Shokaku, only her sister-carrier remained of the once proud Kido Butai that had attacked Pearl Harbor.

As for Shokaku's nemesis, the erstwhile Cavalla had started planing back up to periscope depth at 1352. By now the depth charges had almost stopped. Kossler suspected it was because the escorts had more to think about, for a "loud disturbance" could still "be heard by JP in direction of attack". But no one was prepared for the "four terrific explosions" heard thundering from the target's vicinity from 1408 to 1411. Their rumblings continued for many seconds, and Cavalla's company realized they were not depth charges or bombs, but explosions on the target. Anxious now to determine the situation, Cavalla reached periscope depth at 1421. However, to Kossler's surprise, nothing was in sight. Though admitting "visibility poor due to rain squalls all around", the sub's skipper was elated---he suspected the truth: the detonations had been the death rattle of their target carrier. He said as much to ComSubPac, when - after surfacing at 1851 and running out of the battle area - when he transmitted his attack report at 2125 and added, "believe that baby sank". Though a skeptical Spruance was to spend some anxious hours trying to find and destroy the "damaged Zuikaku " reported torpedoed, ComSubPac concurred with Kossler and credited the Cavalla with sinking a Shokaku-class carrier and subsequently bestowed the Combat Insignia Award for the feat.

Postscript

After losing the carrier Hiyo and suffering more damage in the TF 58 air attack of 20 June, the defeated Mobile Fleet returned to the homeland, anchoring at Nakagasuku Bay, Okinawa on the afternoon of the 22nd. There, survivors of Taiho and Hiyo were transferred to Shokaku's sister carrier Zuikaku. Probably for reasons of space, but perhaps to spare them the disorientation of being aboard a "ghost" of their lost vessel, the Shokaku's survivors were transferred instead to heavy cruiser Maya; upon which they returned home on 24 June. After the loss of his ship, Captain Matsubara Hiroshi returned to Japan and on 30 June was assigned to the Yokosuka Naval District. Shortly after he was transferred to Sasebo as commander of the Naval Barracks, and subsequently finished out the year as an Instructor at the torpedo school.

After sinking Shokaku, the rest of Cavalla's voyage was anti-climatic. Though she remained on patrol till ordered home on 25 July, she sank only a sampan. On 3 August 1944 she returned to Majuro, tying up at 1514 to U.S.S. Bushnell, ending a singularly brilliant First Patrol. The Cavalla went on to garner a sterling record, and was still under Kossler's command when she sank the super-destroyer Shimotsuki in November, taking down ComDesRon 31 with her. After the war, the Cavalla was retained in service after a refit. Once decommissioned, she was not scrapped, but instead has been preserved at Galveston, Texas, where she can be Visited and Seen today!

Note: One source gives the Shokaku's casualties as 1,272 lost, but since the figure above is precisely broken down it was accepted.