Japanese aircraft carrier Shōkaku

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.[4]

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.[4]

Shōkaku was 10,000 tons heavier than Sōryū, 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[4]

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.[5]

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

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.[6]

Shōkaku's 242 m (794 ft) long wood-planked flight deck ended short of the ship's bow and, just barely, short 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), the middle and the rear elevators measured 13 m (43 ft) by 12 m (39 ft).[7] 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.[8]

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 (111–144 km/h; 69–90 mph). A third crash barrier was added and a light collapsible wind-break screen was installed just forward of the island.[4]

The upper hangar was 623.4 by 65.6 feet (190 by 20 m) and had an approximate height of 15.7 feet (4.8 m); the lower was 524.9 by 65.6 feet (160 by 20 m) and had an approximate height of 15.7 feet (4.8 m). Together they had an approximate total area of 75,347 square feet (7,000 m²).[7] Hangar space was not greatly increased in comparison to Sōryū 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.[9]

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.[4]

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.[4]

The presence of this radar however, undoubtedly saved Shōkaku one month later at the Battle of the Santa Cruz Islands, when the ship was bombed by SBD-3 Dauntless dive bombers from USS 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 and explosions that caused most of the carrier sinkings in the Pacific theater.

Shōkaku's primary air defense consisted of sixteen 127 mm (5.0 in) Type 89 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.[4]

Initially, light AA defense was provided by twelve triple-mount 25 mm (0.98 in) Type 96 AA guns.[4]

In June 1942, Shōkaku had her anti-aircraft armament augmented with six triple 25 mm mounts, two each at the bow and stern, and one each fore and aft of the island. The bow and stern groups each received a Type 95 director. In October another triple 25 mm mount was added at the bow and stern and 10 single mounts were added before the Battle of the Philippine Sea in June 1944.

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 the battleship USS South Dakota 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, under Commander Herman J. Kossler. As Shōkaku had been in the process of refueling and rearming aircraft and was in an extremely vulnerable condition, 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. The order to abandon ship was given, 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.[2]