Japan’s Giant Aircraft
By Mike Bennighof, Ph.D.
The loss of four aircraft carriers in the Battle of Midway
in June 1942 shocked the Imperial Japanese Navy. In one battle,
the bulk of its striking force had been destroyed, leaving
only two fleet carriers available and both of them were under
The Japanese would bring two converted passenger liners
into service at about the same time, Junyo on 5 May
1942 and Hiyo on 31 July. Both served as fleet carriers, as
had been intended from their requisition in August 1940, but
were much less capable ships than the four big carriers lost
The Imperial Navy needed more carriers quickly, and ordered
conversion of a number of warships under construction. We
looked at the battleship-carrier hybrids in an
earlier installment. One of the warships slated for complete
conversion to a carrier was the giant battleship Shinano.
Shinano had been projected as the third ship in
the Yamato class: the largest ever built, armed with
nine huge 18-inch guns. Yamato herself was laid down
in November 1937, launched in August 1940 and commissioned
in December 1941. Her sister Musashi was laid down
in March 1938, launched in November 1940 and commissioned
in August 1942.
The next pair of ships was ordered under the 1939 program,
with Shinano laid down in May 1940 and the never-named
Number 111 begun in the graving dock vacated by Yamato
in November 1940. When war began in December 1941, construction
halted on both new battleships, with Shinano about
half finished and her sister 30 percent complete. Construction
on both had been cancelled, but neither had been scrapped
when the search for suitable carrier conversions began in
the summer of 1942.
With construction already halted, Shinano was an
obvious choice. She had been completed only to her armored
deck, allowing reconstruction to begin immediately without
the need to dismantle her superstructure. Work crews began
building a hangar deck on the armored deck in the summer of
1942, before a set of carrier plans had even been produced.
as drawn by Shizuo Fukui.
Vice Admiral Keiji Fukuda, the Yamato class designer,
and Vice Admiral Sei-ichi Iwamura, Chief of the Naval Technical
Bureau, collaborated on the new carrier’s design. The
huge, deep hull would give their new carrier very large magazines
for aerial ordnance and vast storage capacity for aviation
fuel — far larger reserves than those of any other Japanese
carrier, and much more than her own air group could effectively
use in a carrier engagement.
Therefore, the two admirals hit on a novel plan: Shinano
would have no air group of her own. In a carrier battle, she
would serve as a floating station to re-fuel and re-arm the
planes of other carriers’ squadrons. This method, Fukuda
and Iwamura argued, would multiply the squadrons’ effect.
The naval headquarters staff disagreed and directed the designers
to create a conventional carrier. Instead of complying, the
two complained bitterly and loudly to all who would listen
and many who did not, much like modern wargame designers,
and finally obtained a compromise. Shinano would
carry 47 of her own planes, and dedicate half her hangar space
to servicing planes from other carriers. Incorporating the
lessons of war, she had an open hangar with huge steel roll-down
doors for stormy weather unlike the usual Japanese closed
When Shinano floated out of her dock at Yokosuka
Navy Yard on 11 November 1944, she was the largest aircraft
carrier ever built by far, and would remain so until the American
nuclear-powered carrier Enterprise was commissioned
in the early 1960s. At almost 72,000 tons, she retained much
of her battleship protection, though the armor belt had been
reduced from 16 inches to “only” eight. In addition
to the armored hangar deck, she also had an armored flight
deck three inches thick and coated with a non-flammable mixture
of latex and sawdust. Wood fittings were minimized to reduce
risk of fire, and her aviation fuel stores were located deep
within the ship, well below the waterline. She carried her
ammunition stores within the heavily-armored magazines installed
for the 18-inch rifles she would have mounted as a battleship.
An armored bulkhead split the hangar deck in two; the front
section would carry Shinano’s own air group, while the
aft hangar would service other carriers’ planes. Without
the ridiculous service mission, Shinano could have carried
about 70 planes — fewer than Zuikaku and Shokaku,
Japan’s alrgest pre-war carriers. In keeping with Japanese
late-war practice, Shinano had a massive ant-aircraft
battery with over 100 light guns, eight 5-inch dual-purpose
weapons and several rocket launchers (whether all of these
were fitted is not clear).
After some trials in Tokyo Bay, Shinano and four
destroyers headed out for Matsumaya in the Inland Sea on 28
November, where it was hoped she would not be found by American
carrier planes while she completed fitting out. At 2048 she
was spotted by the American submarine Archerfish,
which began stalking the unidentified big ship.
USS Archerfish sank the giant carrier.
Archerfish came in from the stern, usually a losing
proposition for the submarine, but the carrier group gave
up its speed advantage by zig-zagging sharply. By 0317 Archerfish
had a firing solution at the optimum range of 1,400 yards,
and fired all six of her bow torpedo tubes. Four torpedoes
struck Shinano near the stern, and she began to settle
in the water.
The big carrier remained afloat for almost exactly another
seven hours before slipping under the waves and exploding.
For some reason, the fitting of watertight doors at been left
for Matsumaya, and the crew had not yet formed a damage control
organization. Flooding proceded steadily with little interference
from the crew.
In Leyte Gulf we’ve included
two versions of Shinano, both battleship and carrier.
As a battleship, she’s armed slightly differently than
her two sisters, as the Japanese shortage of medium-caliber
guns caused alterations in her planned secondary armament.
Shinano is presented as complete (with watertight
doors and a damage control crew, though the Japanese were
never as good at this task as the Americans). Thus, while
she is not the most capable Japanese aircraft carrier she
is extraordinarily tough to sink, but like any carrier she
can be put out of action fairly easily.
This piece originally appeared in July 2005.
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