Kaga

Japan's first heavy carrier, she was converted from a battleship due to be scrapped under the terms of the 1922 Washington Naval Treaty. Sunk at Midway. - (Jon Parshall)

As completed as aircraft-carrier 1928:
The ship has two main hanger decks and a third auxiliary hanger with a total capacity of 60 aircraft. Her air group consists of 12 Mitsubishi Type 10 1MF (+4 spares) fighters, 24 (+4 spares) Mitsubishi Type 13 B1M3 attack aircraft and 12 (+4 spares) Mitsubishi Type 10 2MR reconnaissance aircraft. However, KAGA doesn’t get her aircraft aboard before November 1929. No catapults are fitted. Her arresting gear is the British longitudinal wire system.

Her defensive armament consists of ten 20-cm (7.9”)/50 3rd Year Type guns; one twin model B turret on each side of the middle flight deck and six in casemates aft. This heavy gun armament is provided in case she is surprised by enemy cruisers and forced to engage battle. She is also given an AA armament of six twin 12-cm (4.7”)/45 10 Year Type Model A gun mounts fitted on sponsons below the level of the funnels (three mounts per side), where they can not fire across the flight decks.

KAGA’s funnel gases are collected in a pair of long horizontal ducts which discharge at the rear of each side of the flight deck. This was a controversial approach, and was part of a deliberate comparison experiment with other solutions. It was roundly criticized by designer Hiraga Yuzuru among others. The concerns were warranted for KAGA's low speed allowed the gases to disturb landing operations at the stern and smoke to fill the non-commissioned officer's quarters. The arrangement would be vastly re-cast at the next major reconstruction.

The machinery consisted of four sets of Kawasaki Brown Curtis geared turbines giving 91,000 shp on four shafts. As a battleship this was projected to give KAGA 26.5 knots. However, because of the just over 6,000 tons reduction in weight as a carrier, KAGA actually achieved 27.5 knots on her November 1928 trials. Steam was provided by twelve saturated steam boilers, eight of them oil-burning, four of the mixed oil/coal type.

Major Reconstruction:

(25 June 1934 to 25 June 1935):
Undocked. KAGA is drastically modified. Her displacement is now increased to 38,200-tons standard with her flight deck and hangers extended to the bow, increasing the flight deck length to 248.55-meters (815.5’) and raising aircraft capacity to 90, including 18 spares. Two experimental catapults are fitted forward but trials are deemed unsatisfactory and their use is abandoned. A third elevator services the extended hangers. Her arrested gear is replaced by a Japanese-designed Type 1 system. A small starboard island superstructure is also installed. (There had been some idea of giving KAGA a larger island with vertical funnel similar to western designs, but the TOMUZURU and Fourth Fleet incidents made the Japanese especially conscious to avoid potential weight issues. As it was, KAGA's starboard forward island arrangement would prevail over the port-side amidships experiment of AKAGI and HIRYU in this regard until TAIHO and SHINANO designs.) The lengthy funnel ducting is replaced by a single downturned starboard funnel.

Her two twin turrets on the middle flight deck are removed and four new 20-cm/50 3rd Year Type No. 1 guns in casemates are added forward of the aft existing ones. Her 12-cm AA guns are replaced by eight twin 12.7-cm (5.0”)/40 Type 89 gun mounts. Their sponsons are raised one deck to allow them some measure of cross-deck fire. 11 twin 25-mm Type 96 gun mounts are added, also on sponsons. Finally, six 6.5-mm Type 11 MGs are also carried. However, KAGA retains her outdated Type 91 AA directors.

KAGA also had to be re-engined, and her boiler room compartmentation re-shaped. She emerged from reconstruction with her eight boilers arranged each in a separate compartment amidships along the midline, port and starboard. The engine rooms retained their general original arrangement: forward engine rooms were immediately abaft, and drove the inboard propellers. Aft and outboard of these were the aft engine rooms driving the outboard propellers.

E June 1935:
Returns to service. Assigned to Car Div 2 consisting of KAGA as only carrier with DesDiv 2’s MINEKAZE and OKIKAZE. Her air group (operational aircraft only) includes 16 Nakajima Type 90 A2N1 fighters, 16 Aichi Type 94 D1A “Susie” dive bombers and 28 Mitsubishi Type 89-2 B2M2 attack planes.

Refits in 1940:
(May 1940 and November 1940):
Her flight deck is enlarged and reinforced. Reportedly, KAGA had three air-propelled catapults installed on the forward end of the flight deck during the refit period starting 1 May 1940. At the same time, an extra pair of support pillars (for a total of three pairs now) for the forward flight deck were added. (Less likely, these were installed in the November drydocking). The experiment was apparently short-lived, and the catapults removed, but their seatings remained visible. It is also possible that the catapult seatings only were completed, and it was never installed. This point remains unclear and the evidence conflicting. It is probably during this overhaul and in this connnection that the additional pair of support pillars are placed forward in-between the two existing pairs.

Her hanger areas are enlarged to accommodate the new generation of aircraft. Her arresting gear is replaced by a Type 3 system and her bridge is modernized. Four additional Type 96 twin 25-mm guns are fitted on sponsons. Her airgroup consists of 12 Mitsubishi A5M4 fighters, 24 Aichi D1A2 bombers and 36 Yokosuka B4Y1 attack planes with another 18 aircraft carried in crates as spares.

Miscellaneous Details and Discussion:

For more information, readers are urged to consult:
Lengerer, Hans.Akagiand Kaga. Parts 1-3.Warship: A Quarterly Journal of Warship History 22 (April, July, and October 1982).