1st Air Fleet (Imperial Japanese Navy)

The Imperial Japanese Navy (日本海軍, Nihon Kaigun) at the beginning of World War II contained the world's largest aircraft carrier fleet. At the centre, was the 1st Air Fleet (第一航空艦隊, Dai-ichi KōKū Kantai) which was a grouping of naval aircraft and aircraft carriers. With the Kido Butai (being its primary carrier battle group) the Imperial Japanese Navy would reign supreme for the first six months after Japan's entry to World War II.

Origins
The origin of the 1st Air Fleet had to do with creating the first carrier based air fleet. In 1912, the Royal Navy had established its own flying branch, the Royal Naval Air Service (RNAS). The Japanese admirals, whose own Navy had been modeled on the Royal Navy and whom they admired, themselves proposed their own Naval Air Service. The Japanese Navy had also observed technical developments in other countries and saw that the airplane had potential. The following year, in 1913 a Navy transport ship, the Wakamiya was converted into a seaplane tender, a number of aircraft were also purchased. The 1st and 2nd Air Fleet were to be the primary attack force of the IJNAS.

Organisation
The Navy Air Services' carrier-based Air Corps or Naval Air Group (Kokutai) was a major component of the Combined Fleet (Rengo Kantai), and whose size (from a handful to 80 or 90 aircraft) was dependent on both the mission and type of aircraft carrier that they were on. Several Kokutai formed a Koku Sentai (Naval Air Flotilla or Carrier Division), while a Naval Air Fleet (Kantai) was made up of several Koku Sentai.

First half as Carrier Task Force
On 10 April 1941 the Imperial Japanese Navy formed the First Air Fleet (Dai-ichi KōKū Kantai) consisting of all seven of Japan's aircraft fleet carriers and light carriers with a total of 474 aircraft. This was a naval battlegroup with the single most powerful concentration of naval aviation in the world. The groundwork for the true carrier task force had been laid.

The large fleet carriers had three types of aircraft; fighters, level/torpedo bombers, and dive bombers. The smaller carriers tended to have only two types of aircraft, fighters and torpedo bombers. The carrier-based kokutai numbered over 1500 pilots with over 1500 aircraft. At the beginning of the Pacific War, there would be 10 large carriers with a total aircraft capacity of about 600.

Kido Butai
The Kido Butai (機動部隊, lit. Mobile Unit/Force) was the Combined Fleet's tactical designation for its carrier battle group. The title was used as a term of convenience; it was not a formal name for the organization. It consisted of Japan's six largest carriers, carrying the 1st Air Fleet. This mobile task force was created for executing the attack on Pearl Harbor under Admiral Chuichi Nagumo in 1941. For the attack on Pearl Harbor, the Kido Butai consisted of 6 aircraft carriers (commanded by Chuichi Nagumo, Tamon Yamaguchi and Chuichi Hara) with 414 airplanes, 2 battleships, 3 cruisers, 9 destroyers, 8 tankers, 23 submarines and 4 midget submarines. However, these escort ships were borrowed from other fleet and squadrons. On 14 July 1942, all carriers were moved to the 3rd Fleet. It was considered the single most powerful naval fleet until four of the six aircraft carriers of the unit were destroyed in the disastrous Battle of Midway.

Commanders

 * Commander in chief


 * Chief of Staff

Second half as Land-based Air Fleet
On 1 June 1943, the 1st Air Fleet was reborn as the land-based Air Fleet. On 30 September 1943, a cabinet meeting planned the Absolute National Defence Zone (絶対国防圏) strategy. The plan intended the Kuril Islands, Bonin Islands, Mariana Islands, Caroline Islands, Geelvink Bay (Biak), Sunda Islands and Burma to be unsinkable aircraft carriers. The 1st Air Fleet became the main force of this plan. However, it was soundly beaten in the Battle of Philippine Sea. The IJN then moved the air fleet to the Philippines to regroup. However, the IJN lost the air fleet, as it was not combat ready in the Aerial Battle of Taiwan–Okinawa. After the battle it had only 30 aircraft. The only tactic left for them was the Kamikaze Attack.

Commanders

 * Commander in chief


 * Chief of Staff

'Some of the commanders of the Kido Butai''

Pearl Harbor
The Kido Butai (also known as the Carrier Striking Task Force) set sail from Hittokapu Bay, Japan under Vice Admiral Chuichi Nagumo on 26 November 1941, arriving in Hawaiian waters on Sunday December 7, 1941 Hawaiian time. At around 8am, the first wave began its attack on the US Pacific Fleet based at Pearl Harbor and on outlying airfields. By the end of the day 21 American ships were either sunk or crippled, 188 aircraft were destroyed and over 3,500 American personnel were casualties of war. Japan was now formally at war with the United States.

For the attack on Pearl Harbor, this fleet had a strength of 103 level bombers, 128 dive bombers, 40 torpedo bombers, 88 fighter planes and plus 91 planes with a total of 441 planes. The Pearl Harbor Attack force composition

Indian Ocean Raid
Between 31 March and 10 April 1942 the Japanese conducted a naval sortie against Allied naval forces in the Indian Ocean. The Fast Carrier Task Force(Kido Butai) consisting of six carriers commanded by Admiral Chuichi Nagumo inflicted heavy losses on the British Fleet, with the sinking of 1 carrier, 2 cruisers, 2 destroyers and 23 merchant ships for the loss of 20 aircraft. Attacks on the island of Ceylon were also carried out.

Battle of the Coral Sea
The 1st Air Fleet dispatched the Fifth Carrier Division in the Coral Sea during the return from the Indian Ocean. On May 7 the USN sighted the Port Moresby invasion force and mistook it for the main carrier force. Admiral Fletcher sent an aircraft strike which sank the IJN light carrier Shōhō. After this loss of air cover, the Port Moresby invasion force abandoned its mission and retreated north. On the same day the IJN sighted and sank USN destroyer Sims and oiler Neosho. The primary action took place on 8 May. Both carrier forces sighted and attacked each other. As a result, Lexington was sunk and Yorktown was damaged by a Japanese air strike. USN aircraft managed to damage Shōkaku which meant that she and her sister ship were unable to participate in the following operation. The remaining fleet returned to Japan to prepare for the Midway invasion (Operation MI).

Battle of Midway
Admiral Isoroku Yamamoto planned to lure and destroy USN carriers by attacking the Midway Islands in June 1942. The Japanese were unaware that the United States had broken their naval code. As a result of this, USN carriers were already in the area when the Japanese attacked Midway. On 3 June US land-based bombers from Midway attacked the Japanese fleet but scored no hits. On 4 June, due to the poor reconnaissance efforts and tactical mistakes of Vice Admiral Chuichi Nagumo, USN dive bombers were able to surprise the Japanese carrier force and destroyed three carriers (Akagi, Kaga and Sōryū). At the time of the attack the Japanese carriers were in the process of preparing to launch an air strike against the US carriers and their hangars were full of loaded aircraft, bombs and aviation fuel which decisively contributed to their destruction. Carrier Hiryū managed to survive the attack and Rear Admiral Tamon Yamaguchi launched a strike against Yorktown. Aircraft from Hiryū managed to cripple Yorktown which was later sunk by a Japanese submarine I-19. In response, US launched a strike against Hiryū and sunk her. That day the Japanese lost four aircraft carriers and much of their experienced aircrew.

Battle of the Eastern Solomons
The battle took place in August 1942. It was one of the two battles around the Solomon Islands where the IJN carrier force engaged USN carrier force. As a response to Allied landings on Guadalcanal in early August, the Japanese planned a counterattack for late August. On 24 August the IJN carrier force (Shōkaku, Zuikaku and Ryūjō) under the command of Vice Admiral Chuichi Nagumo arrived in the Solomons area. Ryūjō was then separated and sent to attack Henderson Field. She was spotted by US reconnaissance aircraft that morning. Admiral Fletcher sent a strike force in the afternoon which sunk her. About the same time the Japanese sighted the US carrier force (Enterprise and Saratoga) and launched an air strike which badly damaged Enterprise.

Battle of Santa Cruz Islands
This was the second carrier battle of the Guadalcanal Campaign. The Japanese Army planned a major ground offensive on Guadalcanal for the end of October 1942. The Japanese Navy was to support this offensive. The IJN force consisted of four carriers (Shōkaku, Zuikaku, Jun'yō and light carrier Zuihō). The USN had two carriers available at the time (Enterprise and Hornet). The two forces first sighted each other in the morning of 26 October. In the following air strikes, the USN managed to heavily damage Shōkaku and Zuihō. In exchange, the IJN sank carrier Hornet and badly damaged Enterprise. Despite the tactical victory of the Japanese at the Battle of Santa Cruz Islands, their experienced aircrew was almost entirely wiped out in the two carrier battles around the Solomon Islands and they were no longer able to conduct carrier operations for some time.

Battle of the Philippine Sea
The Invasion of Mariana Islands in June 1944 came as a surprise to the Japanese who had expected the next US target to be either the Palau Islands or the Caroline Islands. In response, the IJN moved to counterattack the US forces. Vice Admiral Jisaburo Ozawa had five large carriers (Taihō, Shōkaku, Zuikaku, Jun'yō and Hiyō) and an additional four light carriers under his command. By this time, the IJN was able to train new aircrew for their carriers to replace those lost during the battles in 1942, but their training was superficial and they had no combat experience. The US 5th Fleet, under the command of Raymond A. Spruance, had seven fleet carrier and eight light carriers. On 19 June Ozawa launched four successive air strikes against the USN ships but they were all destroyed by the combination of radar, new carrier-borne fighters (F6F Hellcat), and pilots that were better-trained and had much combat experience. That same day USN submarines managed to sink the new Japanese aircraft carrier Taihō as well as Shōkaku. The next day, a USN counter-attack sank carrier Hiyō and damaged three more carriers. Overall the Japanese lost more than four hundred aircraft with their newly trained aircrew.

Battle of Leyte Gulf
After disastrous losses at the Battle of the Philippine Sea, the Japanese carrier force was again practically without aircrew and aircraft. This meant that at the Battle of Leyte Gulf the IJN carrier force was only used as a decoy force where it was ultimately destroyed, the battle that saw the last Kido Butai survivor, Zuikaku, along with Zuiho, Chiyoda and Chitose succumbing to US air attacks of Admiral William F. Halsey's Task Force 38.