Japan is quintessentially by geography a maritime country. It consists of four main islands (Hokkaido, Honshu, Shikoku and Kyushu), no part of which is more than 150 kilometres from the sea, and about 3,000 smaller islands (including Okinawa) and islets, some of which are uninhabited. Its claimed exclusive economic zone (EEZ) is 4.51 million square kilometres, compared to its total land territory of only 380,000 square kilometres. Its coastline is nearly 35,000 kilometres in length (the sixth longest in the world), or 91 metres for every square kilometre of land area.¹ Except for the northernmost island of Hokkaido, the interiors...

Chinese intrusions into Japan’s claimed exclusive economic zone (EEZ), hitherto sporadic, increased rapidly after 1996, when Japan expanded its claims to include the disputed Senkaku Islands (called Diaoyu in Chinese) and other islands in the East China Sea, thus overlapping similar Chinese claims, as well as Okinotorishima in the Philippine Sea, midway between Taiwan and Guam.¹ Moreover, in addition to numerous deployments of ‘oceanographic research’ and signals intelligence (SIGINT) collection ships, the intrusions have increasingly involved warships, including submarines, sometimes acting aggressively.²

Chinese marine research vessels operated actively in Japan’s EEZ 16 times in 1998, 30 times in 1999 and...

The Japanese Maritime Self-Defense Force (JMSDF) has a comprehensive architecture of ocean surveillance systems for monitoring the disparate challenges it faces in supporting its defensive activities, including SOSUS (sound surveillance system)-type submarine detection and tracking systems, high frequency direction finding (HF DF) facilities, ocean surveillance ships, and maritime surveillance aircraft. Information from all of these systems is integrated into the JMSDF’s Ocean Surveillance Information System (JOSIS), the current version of which is officially called the JMSDF OSIS Evolutionary Development (JOED) system, at the JMSDF’s Fleet HQ at Yokosuka, in Kanagawa Prefecture, on the western side of Tokyo Bay.

Japan’s undersea...

The Japanese Ground Self-Defense Force (JGSDF) also has substantial responsibilities and capabilities for coastal surveillance and coastal defence, especially with respect to northern Hokkaido. These responsibilities have been maintained through adroit bureaucratic–political manoeuvring, but their origins go back to the early part of the 20th century when, in 1907, two years after the Imperial Japanese Navy’s decisive defeat of the Russian Baltic Fleet in the Battle of Tsushima, the army ‘reasserted its control over the determination of the nation’s strategic priorities’, with Russia being formally identified as ‘Japan’s prime hypothetical enemy’ and the army’s forward position on the Asian...

The Japanese Maritime Self-Defense Force (JMSDF) is commanded by the chief of the Maritime Staff, based at the Ministry of Defense (MoD) HQ at Ichigaya in Tokyo. From 1954 to 2006, he was supported by the powerful Maritime Staff Office (MSO), which was responsible for all aspects of supervision of the JMSDF, which includes the Self-Defense Fleet, five regional district commands (with HQs at Ominato, Yokosuka, Kure, Maizuru and Sasebo), the Air Training Squadron and various support units, such as hospitals and schools, and including operational command as well as administrative, personnel, training and capability acquisition matters (see Fig. 1)....

The Japanese navy began research on hydrophones in 1920, initially experimenting with foreign models, although it ‘failed to produce a workable copy’.¹ In the early 1930s, after further foreign purchases, it developed systems for installation aboard ships as well as on the sea bottom. The first ship-borne systems, the models 93 and 0, were based on the US MV-type hydrophone, which was imported in 1930; they were deployed aboard all Imperial Japanese Navy (IJN) battleships and destroyers until being superseded in 1943. Research and development was primarily undertaken by the Acoustic Department of the Second Naval Institute at Numazu, on...

The Japanese Maritime Self-Defense Force (JMSDF) installed its so-called ‘first generation’ hydrophone system at several of its new coastal defence stations in the mid-and late 1950s. This used drum-shaped hydrophones, 4 metres in diameter and 2.5 metres high, with a low discrimination capability.¹ The upward-looking arrays were mainly useful for harbour defence, but they could also be strung across key narrow straits. The coastal defence stations established in this period were located at Kannon Zaki, across the Uraga Channel leading into Tokyo Bay; Awaji, on the north-western side of Osaka Bay; Mutsure-jima, astride the entrance to the Kanmon Strait; and...

The US Navy was interested in Japanese locations for its SOSUS (sound surveillance system) stations from the beginning of its SOSUS program, initially called ProjectCaesar, which involved running cables out on continental shelves and connecting them to hydrophones suspended above the sea bottom at optimum signal depths. An ‘experimental station’ was established at the north-western tip of Hokkaido in 1957, with the cable extending into the Soya (La Perouse) Strait. It monitored all the submarine traffic going in and out of Vladivostok and Nakhodka in the Sea of Japan.¹ What was heard, however, ‘didn’t make sense because the collection...

The Japanese Maritime Self-Defense Force (JMSDF) has at least 14 listening stations serving as shore terminals for the underwater hydrophone arrays, but which are typically also equipped with marine surveillance radars sites and electronic intelligence (ELINT) collection systems, and sometimes also with optical observation equipment. A report released by the Council on Security and Defense Capabilities in June 2004 identified 12 ‘coastal surveillance and intelligence collection’ stations (including those at Rebun Island, Wakkanai and Shibetsu in northern Hokkaido identified with Japanese Ground Self-Defense Force (JGSDF) units).¹ The report did not, however, include the two ocean observation stations maintained by the...

The Imperial Japanese Navy (IJN) recognised the utility of aircraft for naval reconnaissance during the First World War, using seaplanes for search missions and, in the 1930s, emphasised the importance of aerial scouting in connection with its emerging doctrine of a first strike against enemy carriers.¹ Naval aviation was revived in the 1950s under US direction and, in the late 1950s, the United States agreed to the Japanese Maritime Self-Defense Force’s (JMSDF) acquisition of Lockheed P2V-R Neptune anti-submarine warfare (ASW)/ocean patrol aircraft. Kawasaki assembled 48 P2V-Rs at its Gifu plant from 1959 through the early 1960s.²

In 1963, Kawasaki initiated...

The Japanese Maritime Self-Defense Force (JMSDF) has a small fleet of ‘oceanographic survey and research vessels’ and other auxiliary vessels that it uses for varied ocean surveillance activities. The fleet includes three ships that are equipped for signals intelligence (SIGINT) collection activities (theNichinanAGS/AGI 5105 and theShonanAGS 5106, operated by the Oceanographic Command HQ at Yokosuka, and theShiraseAGB/AGI 5003 polar icebreaker) and two Surveillance Towed Array Sensor System (SURTASS) ocean surveillance ships (theHibikiAOS 5201 and theHarimaAOS 5202) operated by the Fleet Intelligence Command (FIC) (see Table 3).

The JMSDF’s first ship...

Both the US Navy’s 7th Fleet Command and the Japanese Maritime Self-Defense Force’s (JMSDF) Fleet HQ at Yokosuka receive all intelligence of interest from the US Navy’s Ocean Surveillance Information System (OSIS), its global network of sound surveillance system (SOSUS) facilities, HF DF stations (calledClassic Bullseye), ocean surveillance satellites, and ship-based and airborne sensor systems. The OSIS was developed in the 1970s, and focussed on the Soviet navy. It consisted of a Naval Ocean Surveillance Information Center (NOSIC) at Suitland in Maryland; three Fleet Ocean Surveillance Information Centers (FOSIC), located in London, Honolulu, and Norfolk, Virginia; and two Fleet...

The Maritime Safety Agency (MSA), which was officially renamed the Japan Coast Guard (JCG) in April 2000, is effectively a fourth branch of the Japanese military. Originally established as the Maritime Safety Board in April 1948, it has been reorganised many times since then, and its roles and missions have expanded to include not only guarding Japan’s enormous coastline and providing search and rescue services, but also constabulary operations in the sea lanes and high seas.¹ In May 1998, two MSA vessels were sent to Singapore ready to evacuate Japanese residents from Indonesia, where the political situation was ‘unstable’ and...

The underwater approaches to Japan are now guarded by the most advanced submarine detection system in the world. Some 30 hydrophone arrays form a multi-layered network, with the ocean observation stations at Higashidori in north-eastern Honshu and at White Beach in Okinawa operating long-range, open-ocean systems for surveillance of the eastern and southern approaches to the home islands, and another long-range system deployed across the Sea of Japan for surveillance of the western side; the ‘barrier’ systems, covering the northern and southern entrances to the Sea of Japan (i.e., the Soya and Tsushima straits), and both sides of the Tsugaru...