was an aircraft carrier built for the Imperial Japanese Navy (IJN) during the 1930s. Generally regarded as the only ship of her class, she was built to a modified design. Her aircraft supported the Japanese invasion of French Indochina in mid-1940. She took part in the attack on Pearl Harbor and the Battle of Wake Island. During the first few months of the Pacific War, the ship supported the conquest of the Dutch East Indies in January 1942. The following month, her aircraft bombed Darwin, Australia, and continued to assist in the Dutch East Indies campaign. In April, Hiryū aircraft helped sink two British heavy cruisers and several merchant ships during the Indian Ocean Raid.
After a brief refit, Hiryū and three other fleet carriers of the First Air Fleet (Kido Butai) participated in the Battle of Midway in June 1942. After bombarding American forces on the atoll, the carriers were attacked by aircraft from Midway and the carriers , , and . Dive bombers from Yorktown and Enterprise crippled Hiryū and set her afire. She was scuttled the following day after it became clear that she could not be salvaged. The loss of Hiryū and three other IJN carriers at Midway was a crucial strategic defeat for Japan and contributed significantly to the Allies' ultimate victory in the Pacific.
Design Hiryū was one of two large carriers approved for construction under the 1931–1932 Supplementary Program. Originally designed as the sister ship of Sōryū, her design was enlarged and modified in light of the Tomozuru and Fourth Fleet Incidents in 1934–1935 that revealed many IJN ships were top-heavy, unstable and structurally weak. Her forecastle was raised and her hull strengthened. Other changes involved increasing her beam, displacement, and armor protection.Chesneau 1995, p. 166
The ship had a length of overall, a beam of and a draft of . She displaced at standard load and at normal load. Her crew consisted of 1,100 officers and enlisted men.Jentschura, Jung & Mickel, p. 47
Machinery Hiryū was fitted with four geared steam turbine sets with a total of , each driving one propeller shaft using steam provided by eight Kampon water-tube boilers. The turbines and boilers were the same as those used in the s. The ship's power and slim, cruiser-type hull with a length-to-beam ratio of 10:1 gave her a speed of Brown 1977, pp. 18–19 and made her the fastest carrier in the world at the time of her commissioning.Parshall & Tully, p. 9 Hiryū carried of fuel oil which gave her a range of at . The boiler uptakes were trunked to the ship's starboard side amidships and exhausted just below flight deck level through two funnels curved downward.Peattie, p. 241
Flight deck and hangars The carrier's flight deck was wide and overhung her superstructure at both ends, supported by pairs of pillars. Hiryū was one of only two carriers ever built whose island was on the port side of the ship ( was the other). It was also positioned further to the rear and encroached on the width of the flight deck, unlike Sōryū. Nine transverse arrestor wires were installed on the flight deck that could stop a aircraft. One group of three wires was positioned further forward to allow the ship to land aircraft over the bow, although this was never done in practice. The flight deck was only above the waterline and the ship's designers kept this figure low by reducing the height of the hangars.Brown 1977, p. 18 The upper hangar was and had an approximate height of ; the lower was and had an approximate height of . Together they had an approximate total area of . This caused problems in handling aircraft because the wings of a Nakajima B5N "Kate" torpedo bomber could neither be spread nor folded in the upper hangar.Brown 1977, p. 19
Aircraft were transported between the hangars and the flight deck by three elevators, the forward one abreast the island on the centerline and the other two offset to starboard. The forward platform measured , the middle one , and the rear . They were capable of transferring aircraft weighing up to . Hiryū had a designed aircraft capacity of 64, plus nine spares.
Armament Hiryūs primary anti-aircraft (AA) armament consisted of six twin-gun mounts equipped with 12.7-centimeter Type 89 dual-purpose guns mounted on projecting sponsons, three on either side of the carrier's hull. When firing at surface targets, the guns had a range of ; they had a maximum ceiling of at their maximum elevation of +90 degrees. Their maximum rate of fire was 14 rounds a minute, but their sustained rate of fire was approximately eight rounds per minute.Campbell, pp. 192–193 The ship was equipped with two Type 94 fire-control directors to control the guns, one for each side of the ship;Parshall & Tully, p. 143 the starboard-side director was on top of the island and the other director was positioned below flight deck level on the port side.Brown 1977, p. 20
The ship's light AA armament consisted of seven triple and five twin-gun mounts for license-built Hotchkiss 25 mm Type 96 AA guns. Two of the triple mounts were sited on a platform just below the forward end of the flight deck.Brown 1977, p. 21 The gun was the standard Japanese light AA gun during World War II, but it suffered from severe design shortcomings that rendered it largely ineffective. According to historian Mark Stille, the weapon had many faults including an inability to "handle high-speed targets because it could not be trained or elevated fast enough by either hand or power, its sights were inadequate for high-speed targets, it possessed excessive vibration and muzzle blast, and its magazines were too small to maintain high rates of fire".Stille 2007, p. 51 These guns had an effective range of , and an effective ceiling of at an elevation of +85 degrees. The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the frequent need to change the fifteen-round magazines.Campbell, p. 200 The Type 96 guns were controlled by five Type 95 directors, two on each side and one in the bow.
Armor Hiryū had a waterline belt with a maximum thickness of over the magazines that reduced to over the machinery spaces and the avgas storage tanks. It was backed by an internal anti-splinter bulkhead. The ship's deck was thick over the machinery spaces and thick over the magazines and avgas storage tanks.
Construction and service
Following the Japanese ship-naming conventions for aircraft carriers, Hiryū was named "Flying Dragon".Silverstone, p. 329 The ship was laid down at the Yokosuka Naval Arsenal on 8 July 1936, launched on 16 November 1937 and commissioned on 5 July 1939.Peattie, pp. 239, 241 She was assigned to the Second Carrier Division on 15 November. In September 1940, the ship's air group was transferred to Hainan Island to support the Japanese invasion of French Indochina. In February 1941, Hiryū supported the blockade of Southern China.Hata, Izawa & Shores, p. 131 Two months later, the 2nd Carrier Division, commanded by Rear Admiral Tamon Yamaguchi, was assigned to the First Air Fleet, or Kido Butai, on 10 April.Tully Hiryū returned to Japan on 7 August and began a short refit that was completed on 15 September. She became flagship of the Second Division from 22 September to 26 October while Sōryū was refitting.
Pearl Harbor and subsequent operations
In November 1941, the IJN's Combined Fleet, commanded by Admiral Isoroku Yamamoto, prepared to participate in Japan's initiation of a formal war with the United States by conducting a preemptive strike against the United States Navy's Pacific Fleet base at Pearl Harbor, Hawaii. On 22 November, Hiryū, commanded by Captain Tomeo Kaku, and the rest of the Kido Butai, under Vice Admiral Chūichi Nagumo and including six fleet carriers from the First, Second, and Fifth Carrier Divisions, assembled in Hitokappu Bay at Etorofu Island. The fleet departed Etorofu on 26 November and followed a course across the north-central Pacific to avoid commercial shipping lanes.Polmar & Genda, p. 162 Now the flagship of the Second Carrier Division, the ship embarked 21 Mitsubishi A6M Zero fighters, 18 Aichi D3A "Val" dive bombers, and 18 Nakajima B5N "Kate" torpedo bombers. From a position north of Oahu, Hiryū and the other five carriers launched two waves of aircraft on the morning of 7 December 1941 Hawaiian time.Brown 2009, pp. 116–117Stille 2011, p. 25Japan Standard Time is 19 hours ahead of Hawaiian Standard Time, so in Japan, the attack on Pearl Harbor happened on 8 December.
In the first wave, 8 B5N torpedo bombers were supposed to attack the aircraft carriers that normally berthed on the northwest side of Ford Island, but none were in Pearl Harbor that day; 4 of the B5N pilots diverted to their secondary target, ships berthed alongside "1010 Pier" where the fleet flagship was usually moored. That ship, the battleship , was in drydock and its position was occupied by the light cruiser and the minelayer ; all four torpedoes missed. The other four pilots attacked the battleships and . The remaining 10 B5Ns were tasked to drop armor-piercing bombs on the battleships berthed on the southeast side of Ford Island ("Battleship Row") and may have scored one or two hits on them,Zimm, pp. 159–60, 164, 168 in addition to causing a magazine explosion aboard the battleship that sank her with heavy loss of life. The 6 A6M Zeros strafed parked aircraft at Marine Corps Air Station Ewa (MCAS Ewa),Stille 2011, pp. 49, 51 claiming 22 aircraft destroyed.
The second wave consisted of 9 Zeros and 18 D3As, one of each aborting with mechanical problems. The former strafed Naval Air Station Kaneohe Bay before moving on to attack Bellows Army Airfield. They strafed the airfield, and shot down two Curtiss P-40 fighters attempting to take off when the Zeros arrived and a Boeing B-17 Flying Fortress heavy bomber that had earlier diverted from Hickam Army Airfield, and also destroyed a Stinson O-49 observation aircraftStille 2011, pp. 64–65 on the ground for the loss of one of their own. The fighters with remaining ammunition expended it strafing MCAS Ewa, the rendezvous point for the second-wave fighters.Stille 2011, p. 65 The D3As attacked various ships in Pearl Harbor, but it is not possible to identify which aircraft attacked which ship.Brown 2009, pp. 118–119 Two D3As from Hiryū were lost during the attack, one shot down by Second Lieutenant George Welch.Stille 2011, pp. 66, 70
While returning to Japan after the attack, Nagumo ordered that Sōryū and Hiryū be detached on 16 December to attack the defenders of Wake Island who had already defeated the first Japanese attack on the island. The two carriers reached the vicinity of the island on 21 December and launched 29 D3As and 2 B5Ns, escorted by 18 Zeros, to attack ground targets. They encountered no aerial opposition and launched 35 B5Ns and 6 A6M Zeros the following day. They were intercepted by the 2 surviving Grumman F4F Wildcat fighters of Marine Fighter Squadron VMF-211. The Wildcats shot down 2 B5NsShores, Cull & Izawa, Vol. I, p. 161 before they were shot down by PO3c Isao Towara. The garrison surrendered the next day after Japanese troops were landed.