Kaijō Jieitai - 海上自衛隊 

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Other Forces
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By Hans van Dam

Formation
In 1954, the Self-Defence Law was approved and the Hoancho was replaced by a Boeicho (Defence Agency) and the Keibitai (see pre-1954 aviation units) was reorganised and renamed into the Kaijo Jietai (Japanese Maritime Self-Defense Force) and on 1st July 1954, all its assets were taken on JMSDF charge and reserialled.

Beginning
Initially, all new equipment (but one, a single Kawasaki KAL-2) of the Kaijo Jietai were surplus US Navy aircraft and numbers of North American SNJs and Grumman TBM-3W2 and TBM-3S2 Avengers were delivered to Japan for training purposes. Lockheed PV-2 Harpoons were also delivered and formed a PV-2 patrol unit in September 1955 and were later also used for training. Newly activated Ominato Kokutai received the three Westland WS-51 helicopters in May 1956 and was an operational helicopter unit. Bigger, more modern and complex aircraft came in the form of 16 Lockheed P2V-7 Neptunes, later augmented by 48 Kawasaki built examples, for maritime patrol and 60 Grumman S2F-1 Trackers for ASW. Early 1960, the Neptunes and Trackers formed six Hikotais within three Kokutais (Hachinohe, Kanoya and Tokushima Kokutai) and to train these crews, 35 Beechcraft SNB Expediters, first received in 1957, were used by the Iwakuni Kyoiku Kokutai. ASW helicopter operations commenced in 1958 with the delivery of eight HSS-1 and nine HSS-1N Sea Bat helicopters, forming 101 Hikotai within the Tateyama Kokutai. Other early equipment were small numbers of the Grumman JRF Goose and  Consolidated PBY Catalina, operated by Omura Kokutai, which by 1961 were replaced by the Grumman UF-2 and Douglas R4D aircraft operating from Kanoya. So by early 1960, the JMSDF had seven Air Stations, eight Kokutais divided into multiple Hikotais.

Sixties
A major reorganisation took place in 1961 and the structure as it was set up in September of that year, is still active today. All base Kokutais were disbanded and replaced by Kokuguns (Fleet Air Wing) and these could contain up to three Kokutais (basically the old Hikotais). The Kokuguns came under control of the Koku Shudan (Fleet Air Group/Command) which also controlled some independent Kokutais. All training Kokutais received numbers and fell under the Kyoiku Koku Shudan (Air Training Command). To identify the unit, the Kokutai number or the air station Kana character was painted on the vertical tail. Initially four Kokuguns were formed (1st, 2nd, 3rd and 21st Kokugun), but in September 1962 the 4th Kokugun was activated at Shimofusa for ASW duties. That same year began the replacement of the SNJ by Fuji KM-2s and a year later the replacement of the SNB by Beech 65 Queen Airs. In the nineteen-sixties, helicopter operations intensified enormously and the first serie of rotory equipment changes began. 55 HSS-2, 28 HSS-2A and 84 HSS-2B Sea Kings were built by Mitsubishi between 1964 and 1987 and these supplemented and replaced the older types in use. Another type acquired by the JMSDF was the Kawasaki Vertol 107 of which nine were operated in the minesweeping role between 1963 and 1988. A less significant type was the Sikorsky S-62, which began replacing the S-55 from 1965 onwards and was the prime rescue helicopter during the seventies and eighties. Also for the JMSDF, the local aircraft industrie became a major player this decade. The locally developed turbo-prop powered P-2J, built by Kawasaki first flew in 1966 and entered quantity production at the end of the decade, set to replace the P2V-7. The NAMC YS-11 started to replace the aging R4D with 205 Kyoiku Kokutai and off course the Shin Maywa flying boat made a first flight in October 1967. In the early 1960s Shin Maywa industries started development work for a project designated as the PS-X, the result was the Shin Maywa PS-1 and the two prototypes were handed over to 51 Kokutai at Iwakuni for tests. 

Seventies
The original P2V-7 and Trackers were being gradually replaced by the P-2J, last examples retired in 1982 while the last Tracker left in 1983. The OH-6 replaced the Bell 47 in the helicopter training role with 211 Kyoiku Kokutai, the Beechcraft King Air (TC-90) supplemented and later replaced the Queen Air with 202 Kyoiku Kokutai  with   .  31st Kokugun with 31st Kokutai was activated in March 1973, operating 23 PS-1s from 1973 till 1987. The SAR version, the Shin Maywa US-1(A) replaced the UF-2 from 1976 onwards, serving newly activated 71 Kokutai. Twenty were built and it is still in use and still in limited production, albeit as the US-2. At the end of the decade, the Lockheed P-3 Orion was selected as the replacement for the Kawasaki P-2J.

Eighties to present
Equipment introduced in the seventies and eighties is still largely flying today, although with some types the oldest examples were replaced by new built ones. The Lockheed P-3C Orion replaced the P-2J and PS-1, first examples delivered in April 1981, first operational  Orion unit was newly activated 6 Kokutai (within 4th Kokugun) at Atsugi. At one time, nine operational Kokutais operated the Orion, being 1 to 9 Kokutai and more were serving training unit 203 Kyoiku Kokutai and test unit 51 Kokutai. A few P-2Js were modified to UP-2J and served 81 Kokutai for special support duties. These were later also replaced by special Orions. The Sikorsky H-60 replaced the HSS-2 and S-62, the Fuji T-5 the KM-2 and the Sikorsky MH-53E of which 11 have been delivered, replaced the KV 107. Additional types include the LC-90 which are operated in the transport role and the U-36 which is operating in the operational support role. In March 2008 came another major re-organisation. The eight remaining P-3 Kokutais were reduced to four front-line units, 1, 2, 3 and 5 Kokutai survived. Also all H-60 helicopter Kokutais and air base Kyunan Hikotais were disbanded and four new Kokutais were activated, each with several detachments. Nowadays the Kaijo Jietai is still operating a large fleet of P-3C Orions built by Kawasaki Heavy Industries which currently serve the four operational Kokutais as well as one training Kokutai. Additional special mission Orions serve two units at Iwakuni and the test unit at Atsugi. But the days for the Orion are numbered, some aircraft are withdrawn from use at Atsugi and several examples even scrapped. Kawasaki and the TRDI are in full swing with testing its successor, this time an indigenous designed and developed model, the Kawasaki P-1. Flight testing of this aircraft finished March 2013 and 51 Kokutai is now performing operational tests. 5 Kokutai at Naha is said to receive the first examples after all testing has finished. The SH-60J Sea Hawk is slowly being replaced by the locally updated SH-60K variant and combined fleet is also totalling 100 units. Also the Merlin was introduced, at present supplementing the MH-53Es but at some point in time replacing it as well. Latest helicopter entering service is the Eurocopter EC-135 (TH-135) and it is replacing the OH-6D/DA at 211 Kyoiku Kokutai. As with the Japanese Air Force, today also the Kaijo Jietai is sometimes seen outside Japanese borders on international missions, e.g. the anti-piracy P-3 detachment in Djibouti.

Serial number System
JMSDF aircraft are identified by a four-digit serial number which appears on both sides of the vertical tail and in abreviated form (last two only) in large digits on the fuselage. The first digit of the full serial denotes the primary role, as follows:

  Primary role
1 not used
2 ASW, single-engine
3 not used
4 ASW, two-engined
5 ASW, four-engined
6 trainer
7 communication/trainer
8 helicopter
9 utility/liaison

Sources: Japanese Air Arms 1952-1984 by Akira Watanabe