The (IJNAS) was the air arm of the Imperial Japanese Navy (IJN). The organization was responsible for the operation of naval aircraft and the conduct of aerial warfare in the Pacific War.
The Japanese military acquired its first aircraft in 1910 and followed the development of air combat during World War I with great interest. Japan initially built European aircraft under license, but by the early 1930s Japanese factories were producing domestic designs. The Japanese also embarked on an ambitious aircraft carrier building program, launching the world's first purpose-built aircraft carrier, , in 1922. Several excess battlecruisers and battleships were converted into aircraft carriers as well. As the organization assigned to the IJN's aircraft carriers, the Navy Air Service was tasked with the missions of national air defence, deep strike, naval warfare, and so forth. It retained this mission until its dissolution at the end of the Second World War.
The Japanese pilot training program was extremely selective and rigorous, producing a high-quality and long-serving pilot corps, who were very successful in aerial combat during the early part of World War II in the Pacific. However, as combat casualties mounted starting in 1942, the long duration of the pilot training program, combined with a shortage of gasoline for training, prevented the IJNAS from rapidly providing qualified replacement pilots in sufficient numbers. Moreover, Japan, unlike the U.S. or Britain, never altered its program to speed up the training process of its recruits.
From 1944 onwards, the American naval blockade of Japan began to result in an acute shortage of critical materials required for aircraft production in factories on the Home Islands. This directly affected both the number, quality and type of aircraft available to the IJNAS from mid-1944 onwards. By the end of 1944, many aircraft utilized by the IJNAS were being sent to the front without undergoing any serious testing.
The decrease in both quality and quantity of trained pilots and available aircraft contributed significantly to increasing losses of aircraft and aircrew for the IJNAS toward the end of the war.
Japanese naval aviators, like their army counterparts, preferred maneuverable aircraft, utilizing lightly built but extraordinarily agile planes, most famously the A6M Zero, which achieved its maneuverability by sacrificing armor and self-sealing fuel tanks. Aircraft with armor and self-sealing fuel tanks, such as the Kawanishi N1K-J, would not enter service until late 1944–1945, too late to have a meaningful impact on the outcome of the war.
Early history
Origins
The origins of Japanese naval aviation can be traced to 1912, with the creation of the Commission on Naval Aeronautical Research (Kaigun Kokūjutsu Kenkyūkai) under the authority of the Technical Department. The commission was charged with the promotion of aviation technology and training for the IJN. Initially, the commission focused on non-rigid airships, but swiftly moved on to the development of winged and powered aircraft. That same year, the commission decided to purchase foreign winged aircraft and to send junior officers abroad to learn how to fly and maintain them. The navy purchased two seaplanes from the Glenn Curtiss factory in Hammondsport, New York, and two Maurice Farman seaplanes from France. To establish a cadre of naval aviators and technicians, the IJN also dispatched three officers to Hammondsport and two to France for training and instruction. After their return to Japan at the end of 1912, two of the newly trained naval aviators made the first flights at Oppama on Yokosuka Bay, one in a Curtiss seaplane, the other in a Maurice Farman.
In 1912, the Royal Navy had also informally established its own flying branch, the Royal Naval Air Service. Several Japanese admirals, whose own Navy had been modeled on the Royal Navy, proposed the creation of their own naval air arm. Japanese naval strategists had also observed technical developments in other countries, and foresaw the potential battlefield impact of a strong naval air service. Within a year, the IJN had begun the operational use of aircraft. In 1913, the following year, a Navy transport ship, Wakamiya Maru, was converted into a seaplane carrier capable of carrying two assembled and two disassembled seaplanes. Wakamiya also participated in the naval maneuvers off Sasebo that year.
Siege of Tsingtao
On 23 August 1914, as a result of its treaty with Great Britain, Japan declared war on Germany. The Japanese, together with a token British force, blockaded and subsequently laid siege to the German colony of Jiaozhou and its administrative capital Qingdao on the Shandong peninsula. During the siege, starting from September, four Farman seaplanes (two active and two reserve) on board Wakamiya conducted reconnaissance and aerial bombardments of German positions and ships. The aircraft possessed crude bombsights and carried six to ten bombs that had been converted from artillery shells, released through metal tubes on each side of the cockpit. On 5 September, during the first successful operation, two Farman seaplanes dropped several bombs on the Bismarck battery, the main German artillery position in Tsingtao. The bombs landed harmlessly in the mud, but the aircraft were able to confirm that the light cruiser was not at Tsingtao; this intelligence was of significant importance to Allied naval command. On 30 September, Wakamiya was damaged by a mine and later sent back to Japan for repairs. However, the seaplanes were transferred to the shore and continued to operate against the German defenders until their surrender on 7 November 1914. Wakamiya conducted the world's first naval-launched aerial raids in history and was, in effect, the first aircraft carrier of the Imperial Japanese Navy. By the end of the siege Japanese aircraft had conducted 50 sorties and dropped 200 bombs, although damage to German defenses was negligible.
Further developments (1916–1918) In 1916, the Commission on Naval Aeronautical Research was disbanded and the funds supporting it were reallocated for the establishment of three naval air units (hikotai) which would fall under the authority of the Naval Affairs Bureau within the Navy Ministry. The first unit was established at Yokosuka in April 1916. However, a lack of focused naval air policy in these early years was made apparent by the fact that the Yokosuka Air Group operated with the fleet only once a year, when it was transported briefly to whatever training area the IJN surface fleet was using for maneuvers. Despite this, Japanese naval aviation continued to make progress. In 1917, officers at the Yokosuka Naval Arsenal designed and built the first Japanese seaplane, the Ro-Go Ko-gata reconnaissance seaplane, which was more useful at sea and much safer than the Maurice Farman aircraft that the IJN had previously employed. This aircraft was eventually mass-produced, becoming the mainstay of the navy's air arm until the mid-1920s. By the end of the war, Japanese factories were beginning to turn out engines and fuselages based on foreign designs in increasing numbers. A major enlargement of Japanese naval air strength was part of the 1918 naval expansion program, which established a new air group and a naval air station at Sasebo. In 1918, the IJN secured land around Lake Kasumigaura in Ibaraki Prefecture, northeast of Tokyo. The following year, a naval air station for both land and sea-based aircraft was established, and subsequently, naval air training was transferred to Kasumigaura, from Yokosuka. After the establishment of a naval air training unit at Kasumigaura, the air station became the principal flight training center for the navy.
Interwar development Sempill mission
The Japanese navy had closely monitored the progress and utilization of airpower within the three Allied naval powers during World War I, and concluded that Britain had made the greatest advances in naval aviation. Japanese strategists had also learned a significant amount about naval aviation through wartime contacts within the Royal Navy. In 1920, a Japanese representative had also been sent to Britain to observe air operations off the decks of the British carrier . In 1921, the Japanese government formally requested that the British dispatch a naval air mission, in order to develop and to provide a professional assistance to Japanese naval aviation. Despite reservations on the part of the Admiralty about granting the Japanese unrestricted access to British technology, the British government sent an unofficial civil aviation mission to Japan.
The Sempill Mission was led by Captain William Forbes-Sempill, a former officer in the Royal Air Force experienced in the design and testing of Royal Navy aircraft during the First World War. The mission consisted of 27 members, who were largely personnel with experience in naval aviation and included pilots and engineers from several British aircraft manufacturing firms. The British technical mission left for Japan in September with the objective of helping the Imperial Japanese Navy develop and improve the proficiency of its naval air arm. The British government also hoped it would lead to a lucrative arms deal with Japan. The mission arrived at Kasumigaura Naval Air Station the following month, in November 1921, and stayed in Japan for 18 months.
The Japanese were trained on several British aircraft such as the Gloster Sparrowhawk, as the mission also brought to Kasumigaura over a hundred aircraft comprising twenty different models, five of which were then currently in service with the Royal Air Force, including the Sparrowhawk. These planes eventually provided the inspiration for the design of a number of Japanese naval aircraft. Technicians became familiar with the newest aerial weapons and equipment - torpedoes, bombs, machine guns, cameras, and communications gear. Naval aviators were trained in various techniques such as torpedo bombing, flight control and carrier landing and take-offs; skills that would later be employed in the shallow waters of Pearl Harbor in December 1941. The mission also brought schematics of the most recent British aircraft carriers, such as HMS Argus and HMS Hermes, which influenced the final stages of the development of the Japanese carrier Hōshō. By the time the last members of the mission had returned to Britain, the Japanese had acquired a reasonable grasp of the latest aviation technology and the Sempill mission of 1921–22 marked the true beginning of an effective Japanese naval air force. Throughout the 1920s, Japanese naval aviation continued to be dependent on the British model in both technology and doctrine.
The Japanese military was also aided in the buildup of their naval air force by Sempill himself, who had become a Japanese spy. Over the next 20 years, the British Peer provided the Japanese with secret information on the latest British aviation technology. His espionage work helped Japan rapidly develop its military aircraft and accompanying technologies before the Second World War.
Carrier aviation
Japanese interest in the potential of carrier operations demonstrated by the observations on board Furious led to the inclusion of an aircraft carrier in the eight-eight fleet program of 1918. The 7,470-ton Hōshō was laid down in December 1919 at Yokohama. Hōshō was the second warship after the British to be designed from the keel up as an aircraft carrier, and the first ship to be completed as such from the keel up.