Thoughts on Military History

HIJMS Kaga – CV Imperial Japanese Navy

Originally launched as a Tosa Class battleship, Kaga was saved from Washington Treaty restrictions by the Great Kanto Earthquake of 1923. A sister, Amagi, then under construction was so damaged she was scrapped. Kaga was converted to an aircraft carrier, joining the fleet in 1929 becoming Rengo Kantai’s third CV after the Hosho and Akagi. Kaga was active until sunk at the Battle of Midway, June 4, 1942.

The decision to convert her to a large CV was made in 1923. Earthquake damage necessitated major repairs to the Yokosuka Naval Arsenal before the conversion could be initiated with Kawasaki as partner. Kaga was commissioned in November 1929. Never a beauty as constructed nor after extensive reconstruction to her final form – looking down on Kaga one saw a large battleship hull almost surrounding the flight deck, a robust ship: Japanese naval architects created an ugly duck – a very dangerous ugly duck. As launched Kaga had two flight decks plus an extra hangar with facilities for 60 aircraft. The main flight deck was conventional atop the hull and another on the bow deck: inspiration might have come from HMS Furious and HMS Glorious also with two flight decks. Aircraft takeoff runs on the lower deck started in the lower hanger with recovery simultaneously occurring  on the main deck. Imaginative to say the least. Sizable portions of Tosa’s secondary batteries – 10 20cm guns in casemates remained. More modern aircraft required a longer flight deck, so the two levels on the bow were plated over in a mid 30’s refit.The new deck had no island – good for pilots, not so good for command and control. Exhaust stacks stretched  down each side of Kaga’s hull. The arrangement proved untenable as gases made some quarters unusable, the gasses gave off stench and interfered with flight operations. The final form chosen:stacks pointing downwards just below the flight deck aft the bridge.

 “Kaga was soon judged inferior to Akagi because of her slower speed, smaller flight deck (64 feet (19.5 m) shorter), and problematic funnel arrangement. Because of Kaga‘s perceived limitations, she was given priority over Akagi for modernization.” The refit commenced in June 1934. Lower fight decks became hangars able to take 90 aircraft – a respectable number even today. The fight deck was modified to take a small island – major improvement, new power plant and propellors, her center of gravity was lowered and further torpedo bulges added. Anti aircraft armament was greatly improved. Weaknesses remained, avgas tanks were built directly into the ship. Any vibrations from hits or other causes could cause rupture along with procedures dictating aircraft were to be fueled in hangars instead of the flight deck. Poor armor protection on the flight deck and in the hangars was glaring and the ships fire extinguishing system had no redundancies – all proving fatal to the CV.

During the decade of the thirties, Kaga was very active in the China Conflict paired with Akagi (a conversion from a BC) as flagship of the First Carrier Division (1stCarDiv). She served after the Marco Polo Bridge Incident providing air support to the Army in Shanghai waters. 10 air to air victories were claimed by Kaga’s air group during August/September 1937. Conflicts in China were priceless to the IJN as tactics, ship handling and air operations were finely tuned. Kaga’s airgroup scored the IJN’s first air to air victory – a Boeing P 12 flown by an American pilot – on February 22,1932. She steamed off China from October 1937 until December 1938, returning to Sasebo for provisioning twice. Kaga’s Air Group was involved in the Panay Incident that seriously damaged USA/Japan relations. Refitted between November 1939 and November 1940, the bridge was modernized and the ship overhauled. Hangars were enlarged to fit more aircraft.

Among the lessons learned in China, Concentration: all carriers were concentrated in the new First Air Fleet. Strikes would be formed from all carriers rather than singly. Yet Japanese anti aircraft capability remained poor, the 25mm cannon, deployed in large numbers throughout the fleet during the war, was a sadly ineffective anti aircraft weapon. CAP’s deployed too few aircraft, radio communication between ship-aircraft was poor and most serious, no radar even as US CV’s were fitted with it. 

Kaga lost 15 aircraft at Pearl Harbor: 5 B5N’s (‘Kate’), 4 A6M2’s (‘Zero’) and 6 D3A (‘Val’). In January 1942 she supported the invasion of Rabaul and raided Kavieng Island. After hitting a reef in the Palau area she received temporary repairs at Truk enabling her to sail with the First and Second Carrier Divisions to the Timor Sea launching the air raid on Port Darwin, Australia. Entering dry dock from March 27 to 4 May for  repairs to her damaged bow. The ship  was unable to steam in the Indian Ocean Raid. 

The Doolittle Raid birthed Midway: the results are known to all (TOMH hopes). After launching at 0920 on June 4th, Kaga’s CAP shot down all the TBD’s of VT 8 from  Hornet. There was one survivor, Ensign George Gay Jr. Kaga’s CAP disposed of another 10 TBD’s of VT 6  from Enterprise. At 1022 Kaga was hit by a 1000 lb. bomb dropped by an SBD (‘Dauntless’) from the Enterprise, plus three 500 pounders. A 500 lb. bomb penetrated the upper hanger and exploded causing uncontrollable fires. Captain Okada and most of his Staff were killed by a 500 lb. bomb exploding near the bridge. “The explosions ruptured the ship’s avgas lines, damaged both her port and starboard fire mains and the emergency generator powering her fire pumps,as well as knocking out the carbon dioxide fire suppression system.^[63] Fueled by the avgas pouring onto the hangar deck, the fires detonated the 80,000 pounds (36,000 kg) of bombs and torpedoes strewn across the hangar deck in a series of catastrophic multiple fuel-air explosions that blew out the hangar sides. Mains ruptured, the fire extinguishing system was damaged as were the ship’s generators. Survivors left after 1400. Kaga was scuttled by 2 torpedoes from DD Hagikaze at 1925. 

…“an injured Kaga B5N aircrew member rescued by Hagikaze, described the scene: “My comrade carried me up to the deck so I could see the last moments of our beloved carrier, which was nearby. Even though I was in pain tears started to run down my cheeks, and everyone around me was crying; it was a very sad sight.” 811 went down with Kaga. She lies at 17000 ft under the surface.Debris has been discovered by Robert Ballard, but the main wreck has not been found.

Displacement:38,200 long tons (38,813 t) (standard)

Length:247.65 m (812 ft 6 in)

Beam:32.5 m (106 ft 8 in)

Draft:9.48 m (31 ft 1 in)

Installed power:127,400 shp (95,000 kW)

Propulsion:4-shaft Kampon geared turbines, 8 Kampon Type B boilers

Speed:28 knots (52 km/h; 32 mph)

Endurance:10,000 nmi (19,000 km; 12,000 mi) at 15 knots (28 km/h; 17 mph)

Complement:1,708 (after reconstruction)

Armament:10 × 1 – 200 mm (7.9 in) guns,^[2]8 × 2 – 127 mm (5.0 in) guns,11 × 2 – 25 mm (0.98 in) AA guns

Armor: Belt: 152 mm (6.0 in),Deck: 38 mm (1.5 in)

Aircraft carried:90 (total); 72 (+ 18 in storage) (1936)21 Mitsubishi A6M Zero,27 Aichi D3A,27 Nakajima B5N (7 Dec. 1941)^[3]

Werneth, Ron (2008). Beyond Pearl Harbor: The Untold Stories of Japan’s Naval Airmen. Atglen, Pennsylvania: Schiffer Military History

Parshall, Jonathan; Tully, Anthony (2005). Shattered Sword: The Untold Story of the Battle of Midway. Dulles, Virginia: Potomac Book

Bōeichō Bōei Kenshūjo (1967), Senshi Sōsho Hawai Sakusen. Tokyo: Asagumo Shimbunsha.

Peattie, Mark (2001). Sunburst: The Rise of Japanese Naval Air Power 1909–1941. Annapolis, Maryland: Naval Institute Press. ISBN 1-55750-432-6.

Parshall, Jonathan; Tully, Anthony (2005). Shattered Sword: The Untold Story of the Battle of Midway. Dulles, Virginia: Potomac Books. ISBN 1-57488-923-0.