Japan entered the Second World War with the best torpedo bomber of any nation, the B5N 2 Kate. Their dive-bomber, the D3A 1 Val, while somewhat outmoded by wartime developments, was a very stable platform for dive-bombing and in the hands of a capable pilot, achieved remarkable results. Both of these aircraft were the result of late 1930’s efforts to modernize carrier attack planes. Of course, the Zero fighter is well known among aviation buffs and the general public, but little is printed about the aircraft that delivered the initial punch in the Pacific war or the planes that replaced them later in the war.

The Kate was developed from a 1937 design for an all-metal low wing monoplane to deliver torpedoes against enemy shipping. The version that entered the Pacific war was the –2. It had a top speed of over 200 mph, vastly superior to America’s TBD 1 Devastator of which it was a contemporary. 144 of the aircraft flew from the Kido Butai to cripple the U.S. Pacific Fleet
at Pearl Harbor and they delivered fatal hits to the U.S. carriers Lexington, Yorktown and Hornet at Coral Sea, Midway and Santa Cruz. The B5N had a clean  configuration with a completely retractable undercarriage and an enormous wing which folded allowing a relatively small carrier stowage signature. The Kate was quite successful in the first two years of the war despite its lack of protection for the crew and fuel tank and the minimal rear defensive armament of a single 7.7 mm popgun. After 1943, increasing numbers of advanced U.S. fighters made it difficult to survive in a daylight attack mode. Eventually, staggering losses forced its relegation to second line duties where its long endurance made it suitable for anti-submarine and reconnaissance roles. A total of 1,149 Kates were built by three different manufacturers.

The Val was also designed in 1937, and though flight testing began in 1938, the first qualification aircraft were not delivered to carriers until 1940. Though appearing obsolescent because of its fixed under-carriage, it was fast, quite nimble, and an excellent dive bombing platform that sank more Allied warships than any other Axis aircraft. The fixed undercarriage waspreferred because it was believed that the complexity of a retraction mechanism would counter any gains in performance due to reduction in drag. Beginning with the Hawaiian Operation, in which 126 Vals took part and only 15 were lost, the D3A greatly contributed to Japanese advances in the Pacific and Indian Oceans. The plane’s maneuverability gave it a good chance to survive against early war fighters. The Val suffered from a lack of pilot armor and self-sealing fuel tanks which made it vulnerable to U.S.N. Grummans in an unescorted attack. As long as an heavy escort could be provided, it performed flawlessly. The D3A 2 was introduced after 1942 but the changes were mostly cosmetic and its survivability was not improved.

At the end of the war a shortage of aluminum caused Aichi to design a wooden Val with some slight dimensional changes to accommodate the new material, however only a few were completed before the end of hostilities. By 1943, a more advanced design, the Yokosuka D4Y Judy began replacing D3A’s in depleted carrier squadrons and the Val was demoted to land based
units and small carriers that had inadequate deck space to handle the higher landing speed of the Judy. A total of 1,495 Vals were produced, mostly by Aichi.The D4Y Judy was very fast for a bomber, over 300 mph, and carried its bomb load internally which gave it clean lines that somewhat resembled the Heinkel He118, on which the design was based. Unlike the German plane however, the D4Y did not have crew or fuel tank protection. After the Battle of the Philippine Sea in June 1944, in which 174 D4Y’s achieved little success due, more to unskilled aircrew, protection flaws and superior U.S. fighter direction, the Judy was used for high speed reconnaissance and as a night fighter. There was even a single seat version developed solely for Kamikaze attacks. It was a worthy successor to the D3A but came at a time in the war when Japanese aviation was largely inferior to the Allies.

The follow on to the Kate was the Nakajima B6N Jill. Like the Judy, it was faster than the B5N and even included a
ventral machine gun as in the TBF Avenger. Unfortu-nately, it underwent over two years of development problems although the prototype was ready prior to the Pearl Harbor attack. By the time it was introduced to the fleet, there were few experienced pilots to fly it and fewer carriers to operate from, thus it came into service primarily as a shore based aircraft and was particularly aggressive during the Okinawa campaign both in the conventional attack and Kamikaze roles. As late in the war as it was introduced, it still did not have self sealing fuel tanks. They tried this modification during testing but found that it resulted in a 30% reduction in fuel capacity, so it was discarded and an expected higher loss rate was accepted. In service, the B6N performed well but its high wing loading and landing speed restricted its use to the largest carriers and land bases. The overwhelming U.S. air superiority and the poor quality of Japanese pilots negated any technical or performance advances by the Japanese aircraft industry. To most Americans, the Kate and Val personify Japanese carrier aviation strike forces. They operated when Japan was on the offensive and had intact carrier fleets and quality pilots. Their replacements, however advanced technically, fought at a time when Japanese carriers were in sharp decline and U.S. fighter strength was at its zenith of both aircraft and pilot quality. Their accomplishments suffered accordingly and they are much less well known than the Kate and Val.

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