The defence policy of Japan reflects the unusual position of the country. Although it is a major diplomatic and economic power, and one with a historical reputation of military aggressiveness, Japan resists the development of armed forces with a military capability for military power projection. A military proscription is included as Article 9 of the 1947 constitution stating, "The Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as a means of settling international disputes." That article, along with the rest of the "Peace Constitution," retains strong government and citizen support and is interpreted as permitting the Self-Defense Forces (SDF), but prohibiting those forces from possessing nuclear weapons or other offensive arms or being deployed outside of Japan.
The SDF are under control of the Ministry of Defense, subordinate to the prime minister. Although highly trained and fully qualified to perform the limited missions assigned to them, the SDF are small, understaffed, and underequipped for more extensive military operations. Its activities are confined to disaster relief and limited UN peacekeeping efforts.
Japan's national defense policy has been based on maintaining the 1960 Treaty of Mutual Cooperation and Security with the United States, under which Japan assumed unilateral responsibility for its own internal security and the United States agreed to join in Japan's defense in the event that Japan or its territories were attacked. Although the size and capability of the SDF have always limited their role, until 1976 defense planning focused on developing forces adequate to deal with the conventional capabilities of potential regional adversaries. Beginning in 1976, government policy held that the SDF would be developed only to repel a small-scale, limited invasion and that the nation would depend on the United States to come to its aid in the event of a more serious incursion.
The Soviet invasion of Afghanistan in 1979 and the buildup of military forces in the Soviet Far East, including the Kuriles, a group of islands to the north of Hokkaidō, which were occupied by the Soviet Union but claimed by Japan, led Japan to develop a program to modernize and improve the SDF in the 1980s, especially in air defense and antisubmarine warfare. In the early 1990s, the government was reevaluating its security policy based on reduced East-West tensions.
The Japanese government valued its close relations with the United States, and it remained dependent on the United States nuclear umbrella. Thus, it worked to facilitate military contacts and to support the United States diplomatically whenever possible. Both the government and the public, however, supported only limited increases in self-defense capability. National security, it is believed, is fostered by international diplomacy and economic aid as much as by military might. Though Japan is worried that the United States nuclear umbrella might not remain there in future and with growing Japanese concern over Chinese and North Korean regional domination, Hideyoshi Kase the former senior adviser to Prime Minister and Japan's Defense Agency's former director general, Nakasone Yasuhiro says in an interview with Mitch Anderson's The World Without US: "If United States withdraws its forces from Japan, we will spend the next ten years re-arming in various ways, including acquiring nuclear weapons".