The very first super aircraft carrier was not built by United States. It was Imperial Japan’s 70,000 tonne Shinano built during World War II. Though she met a quick, humiliating end without ever seeing battle.
Japan originally intended to build four 72,000 tonne Yamato Class battleships. Only two, Yamato & Musashi were commissioned. To this day they remain the largest, heaviest, most powerful battleships ever built.
Third of the class Shinano, was suspended mid-construction with 80% of her hull completed, following the sinking of British battleship’s Prince of Wales & Repulse by Japanese aircraft on Dec. 10, 1941.
Prince of Wales & Repulse had no land based air cover, nor were they accompanied by aircraft carriers. Japanese admirals were as sobered by this lesson, as the Royal Navy Admiralty itself.
The Japanese considered scrapping Shinano. Until the loss of four aircraft carriers at the June 1942 Battle of Midway, and their entire air wings. This prompted the decision to complete Shinano as an aircraft carrier.
Though not the first conversion from a non-aircraft carrier design, it was the largest such endeavor. The second largest were the 1920’s US Navy converts Lexington & Saratoga from battle cruiser designs.
However, Japanese industry was abysmally slow to modernize and standardize during the war. Shinano was barely nearing completion over two years after the Battle of Midway.
On November 29, 1944, while underway from Yokosuka to Kure to complete her fitting out, she was sunk by four torpedoes fired by the US Navy submarine Archerfish. Shinano‘s battleship sisters, each took 17 to 18 direct hits with torpedoes and armor-piercing bombs before their identical hulls were compromised enough to sink.
Shinano set sail without water tight doors installed, and numerous other structural compromises to water tight integrity. Though her captain asked to delay transit until these problems were rectified, permission was denied by higher command. A humiliating end, due to carelessness.
Had Shinano survived and deployed operationally, she would have been equivalent in her day to a modern super carrier. 70,000 tonnes displacement, with an air wing of 120 combat aircraft; a battery of 60 anti-aircraft guns; and top speed of 30 knots.
Her only rival in the mid-1940’s would have been America’s USS Midway; at 45,000 tonnes displacement, air wing of 130 combat aircraft, battery of 70 anti-aircraft guns, and top speed of 33 knots. Though, Midway was not commissioned until just after VJ Day.
The difference in tonnage is due to Shinano retaining heavy hull armor from the original battleship design. Midway was designed keel up as an aircraft carrier, without heavy hull armor.
However, Midway and her sister ships Coral Sea & Roosevelt, never attained super carrier status mainly due to displacing only 9,000 tonnes more than the preceding Essex Class carriers. And, as the jet age dawned, and aircraft consequently grew larger, carrier air wings dipped back under 100 planes due to lack of shipboard space.
The next super carrier, USS Forestall, came along in 1955. 82,000 tonnes displacement; air wing of 100 aircraft; speed of 33 knots. But, only eight 5-inch guns since air defense was becoming the exclusive realm of escorting guided missile cruisers.
However, Japan still holds the crown as having built the first super-carrier. As well as retaining the record for the largest, most powerful battleships ever built.