Defence policy of Japan 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 weapon s or other offensive arms or being deployed outside of Japan . Even under these constraints Japan has developed technologically very advanced defense capabilities . Despite the informal limit that sets Japanese defense expenditure to about one percent of GDP its defense spending has been one of the biggest in the world for several decades . 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 " .