The Imperial Japanese Navy (Nihon Kaigun) in 1941 was unquestionably a world power. With the help of the British, who trained the Japanese to the point that all bridge orders were issued in English, a Japanese fleet was built in the early twentieth century. At first the Japanese Imperial Navy was built overseas in England, but soon Japanese yards were building Japanese ships based on English designs. Soon Japanese ships were native designs equal or better to anything afloat.
The goal was to emulate the nations the Japanese perceived as the most powerful nations. The Navy emulated the reigning sea power, England, while the Army modeled itself on the Imperial German Army. When the two European powers went to war in 1914, Japan joined the Allies but expected Germany to win. The Army was surprised by Germany’s defeat, but the nation was happy to occupy Germany’s Chinese and Pacific possessions.
The Treaty of Versailles and the later Treaties of Washington (1920) and London (1930) limited the Japanese. The Navy was upset with the officers who negotiated the treaty, including Isoroku Yamamoto. The officers countered with the charge that a war with the west would be suicidal, because of the superior industrial output of the west.
Yamamoto was a vocal advocate for peace, and was targeted for assassination by the right wing extremists. Admiral Osami Nagano, the Supreme Commander, transferred him to take command of the Imperial Japanese Navy, which saved his life.
What the radicals did not understand was that their was a complete lack of coordination between the army and the navy. Naval officers were sent to Washington and London, and Army officers were sent to Moscow. The two branches of the Armed Forces perceived very different opponents. The naval officers, who toured the United States and attended American colleges (Yamamoto studied at Harvard) saw firsthand the immense industrial output, which even though it was idled by the depression, was still capable of greater output than the Japanese economy.
While Japan led the world in operational aircraft carriers in 1941, the production of carriers in the United States would outpace the Japanese by 1943. While the Japanese built additional 10 carriers by 1945, the Americans built over 150 of all sizes.
The Japanese had other advantages in December 1941. Their ships were better coordinated, especially during night actions. Their aircraft were better than the British or the Americans. The Japanese Mitsubishi Type 00 fighter, codenamed Zeke by the Allies, was more maneuverable than either the US Navy Grumman F4F Wildcat or the British Supermarine Spitfire Mark V. To achieve this, it sacrificed armor protection and self-sealing fuel tanks.
But by 1943, the Japanese would be losing their trained officer core while the Americans were gaining bitter and bloody experience in night fighting. The new F4U Corsair and F6F Hellcat, combined with USAAF P-51 and P-47 fighters, were better than the Japanese A6M Zero, which was in service until the end of the war.
Bu the biggest problem with Japan’s navy during the war was the lack of training. The number of hours that the naval pilots had in 1941 would never be achieved again during the war. While American pilots had several hundred hours in the air, Japanese pilots were limited by lack of fuel to some 50 hours before combat. The Japanese never had a sustained pilot training program to turn out large numbers of pilots.
In August 1945, the last remaining ships of the once proud Imperial Japanese Navy, without their Imperial insignia, were scuttled or transferred to the Allies. The last Japanese battleship afloat, the IJN Nagato, was sunk off Bikini Atoll in 1946 as part of the atomic weapons tests.
The other ships, including the entire fleet that attacked Pearl, was on the bottom of the Pacific. Only a few destroyers and submarines were left. Rusting hulks dotted the shores of Kure and many other ports once held by the Nihon Kaigun.