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 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
thumb|Seaplane carrier [[Japanese seaplane carrier Wakamiya|Wakamiya]]
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
thumb|[[Yokosuka Ro-go Ko-gata, the first domestic designed and built seaplane]]
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.