The expansion of military capabilities in the Soviet Far East beginning in 1970 was of grave concern to Japan, and Japanese authorities regularly monitored the activities of the Soviet Pacific Fleet and Soviet aircraft in the waters and air space around Japan. Despite a general lessening of world tensions and Soviet overtures for improved bilateral relations, in 1990 the Soviet Union still maintained a variety of units, including a division headquarters, on the southernmost Kuril Islands claimed by Japan as its Northern Territories. The Soviet Union also operated about 100 major surface war ships and 140 submarines (about seventy-five nuclear powered) out of Vladivostok and other Pacific ports. Soviet naval combatants passed through the Soya, Tsugaru, and Korea straits and sailed in the Sea of Japan, in the Sea of Okhotsk, and in Pacific Ocean areas adjacent to Japan (see fig. 1). Japan also was within range of Tu-22M Backfire bombers and sea- and air-launched cruise missiles and tactical nuclear weapons based in the Soviet Union. However, with the breakup of the Soviet Union in 1991 and Russia's preoccupation with domestic economic and political problems, Japan has become more concerned about Russia's contributing to a stepped-up global arms trade and nuclear proliferation than about any direct threat from Russia's military forces.
An area of greater strategic interest to Japan is the Korean Peninsula. The Democratic People's Republic of Korea (North Korea) and the Republic of Korea (South Korea) have remained implacable enemies since the Korean War, and the border between them is one of the most heavily fortified in the world. Stable and peaceful relations between the two Koreas are considered vital to Japan's interests: an outbreak of hostilities would involve United States forces stationed in Japan, presenting political and possibly security problems for the nation, in addition to interrupting its flourishing trade with South Korea. Although Japan maintains formal diplomatic relations only with South Korea, it has refused to contribute to that nation's defense, stating that any aid to a foreign military establishment would violate its own constitution.
North Korea's attempts to develop nuclear weapons coupled with its capability to target Japan with any weapon that it developed, is a matter of great concern to Japanese military strategists. In May 1993, North Korea test fired a Nodong-1 intermediate-range ballistic missile with a 1,000-kilometer range in the Sea of Japan, showing that it had the capability to strike Japan.
Events on the Asian mainland could also affect Japan. From the early 1970s, China possessed a nuclear force capable of striking Japan and a large standing army and substantial navy, even though the navy is geared primarily to coastal defense. China itself is unlikely to present a direct military threat to Japan, but Chinese internal unrest or China's conflicts with its neighbors could have an indirect impact on Japanese security and trade (see Trade and Investment Relations , ch. 5).
The nation is vitally dependent on maintaining access to regional and worldwide shipping lanes and fishing areas, but it is incapable of defending the sea routes on which it relied. Its energy supplies came primarily from Middle Eastern sources, and its tankers had to pass through the Indian Ocean, the Strait of Malacca, and the South China Sea, making them vulnerable to hostilities in Southeast Asia. Vulnerability to interception of oceangoing trade remained the country's greatest strategic weakness. Efforts to overcome this weakness, beginning with Prime Minister Suzuki Zenko's statement in May 1981 that Japan would attempt to defend its sea lines of communication (SLOC) to a distance of 1,000 nautical miles, met with controversy. Within the Defense Agency itself, some viewed a role for the MSDF in defending the SLOC as "unrealistic, unauthorized, and impossible." Even the strongest supporters of this program allowed that constitutional and other legal restrictions would limit active participation of the MSDF to cases where Japan was under direct attack. Japan could, however, provide surveillance assistance, intelligence sharing, and search-and-rescue support to United States naval forces.
Japan's small size, its geographically concentrated industry, and the close proximity of potentially hostile powers all render the country vulnerable to a major nuclear strike. As for defense against conventional aggression, strategy is determined by the nation's elongated insular geography, its mountainous terrain, and the nearness of the Asian mainland. The terrain favors local defense against invasion by ground forces, but protection of the approximately 15,800-kilometer coastline of the four main islands would present unique problems in the event of a large-scale invasion. Potentially hostile aircraft and missile bases are so close that timely warning even by radar facilities might be difficult to obtain.
Maneuver space is limited to such an extent that ground defenses would have to be virtually in place at the onset of hostilities. No point of the country is more than 150 kilometers from the sea. Moreover, the straits separating Honshu from the other main islands restrict the rapid movement of troops from one island to another, even though all major islands are now connected by bridges and tunnels. Within each island, mountain barriers and narrow roads restrict troop and supply movements. The key strategic region is densely populated and highly industrialized central Honshu, particularly the area from Tokyo to Kobe (see Physical Setting , ch. 2).
Data as of January 1994