His Majesty's Imperial Japanese Navy in the middle of World War II decided to convert several of its surface warships to hybrid Strike Carriers. This was due to the loss of several flattops at the Battle of Midway and what was thought to be the growing obsolescence of surface ships to aircraft at Pearl Harbor, Taranto, and the loss of Force Z. Originally the naval staff outlined a plan to convert all of Emperor’s battleships and heavy cruisers except for the pair of huge 18" gunned Yamato class behemoths to carriers. Proving over-ambitious only the damaged heavy cruiser Mogami and a pair of 25-year old Battleships (Hyuga and Ise) were converted.
Beginning of WWII and Conversion
The two elderly Battleships had spent the first two years of the war almost entirely in Japanese waters. There they had been attached to the Reserve Fleet along with two even older Fuso-class battlewagons forming Battleship Division Two. The original conversion was to be a straightforward flattop design that would see the shipped stripped of their weapon suite and covered with a flat-top capable of carrying 60-70 conventional aircraft. Lacking the time, resources and above all the aircraft needed to fill them, the ships were modified to where the rear portion of the vessel would be modified and the ships amidships and foredeck would remain the same. Four of the ships dozen 14" (360mm) guns were removed and replaced with a 70 foot flat deck that was constructed of 8 inches (200mm) of concrete augmented with armor plating. More than 100 25mm antiaircraft guns as well as batteries of anti-aircraft rockets were also installed. Thus configured the heavily armored hybrid flat-tops were capable of carrying some 22-24 strike aircraft while still carrying eight large guns and a healthy command and control area.
Operations as Hybrid Carriers
The modifications to the ships commenced throughout 1943. Without the planes and trained crews to fly them the pair subsequently were pressed into service escorting convoys to and from embattled Truk and Singapore in 1943 and 1944 with no embarked air wing. Both the Ise and Hyuga fought in the Battle off Cape Engaño with Ozawa's "Northern Force" in October 1944 as part of the naval campaign in the Leyete Gulf. As a testament to the low numbers of aircraft available to the Japanese Navy the four traditional carriers had a total of 108 aircraft embarked during this battle and two hybrid-battleship carriers none at all. Facing the Japanese task force were no less than 10 US carriers, six modern battleships and more than 600 aircraft. Escaping with minor damage while most of the Japanese force went to the bottom the two Japanese battleships searched for but narrowly missed engaging US Rear Admiral DuBose's small force of destroyers and cruisers which they had a distinct advantage over. Had they encountered DuBose they would have written a much more interesting chapter in their history.
The Sinking of the Ise and Hyuga
Returning to Japanese home waters after the Battle off Cape Engaño, the two ships ended their careers in waves of US aircraft carrier strikes. Neither of the Japanese battleships hybrids had ever seen combats in their new role as aircraft carriers. The Ise sat camouflaged in Kure harbor as one of the endangered species that was intact Japanese warships. She endured massive attacks from US carrier planes from March to July, finally listing and settling on the bottom of Kure harbor on July 28, 1945 after taking sixteen bomb hits. On the same death day as her sister, the Hyuga's crew ran her hard aground in Niro Bay just over two weeks before Emperor Hirohito gave a recorded radio address to the nation calling for surrender. Both ships were broken up over the course of the next two years and scrapped.
Epilogue
The navy of Soviet Russia built the Moskva and Kiev classes of hybrid cruiser-carriers in twenty years later that greatly resemble the same concept of the modified Ise class ships. An abortive US effort in the 1970s referred to as the CSGN Strike Cruiser and even a proposed conversion of the mothballed USS Iowa class battleships was canceled by the Carter administration. The Hyuga's name was recycled in 2009 for a new Japanese warship. Fittingly, the new Japanese Self Defense Force ship JS Hyuga is a 18,000 ton hybrid-aircraft carrier and is Japan's largest surface warship afloat. It remains to be seen if her sister ship currently under construction will be named Ise.
Sources:
Howarth, Stephen The Fighting Ships of the Rising Sun: The Drama of the Imperial Japanese Navy, 1895-1945. Atheneum. 1983
Jentsura, Hansgeorg Warships of the Imperial Japanese Navy, 1869-1945. Naval Institute Press. 1976
Janes Fighting Ships (1914-2006 editions)
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