In Japan, the Japan Self-Defense Force's (JSDF) primary concerns are perceived threats posed by China and North Korea, as well as protecting the country’s territorial waters, countering piracy and terrorism, and conducting humanitarian operations; it exercises regularly with the US military and increasingly with other regional countries, such as Australia; the ground forces are organized into 10 divisions and a number of independent brigades, which include airborne, air assault, and amphibious rapid reaction forces; the maritime force is one of the largest and most modern navies in the world; its principal warships include four helicopter carriers (two are undergoing conversion to light aircraft carriers), more than 40 destroyers and frigates, three landing platform/dock (LPD) amphibious assault ships, and more than 20 attack-type submarines; it also has a large force of maritime aircraft, including over 150 for anti-submarine warfare; the Air Self Defense Force has over 300 modern combat aircraft, as well as more than 200 other aircraft for surveillance, early warning, electronic warfare, search and rescue, transportation, and logistics

Japan’s alliance with the US (signed in 1951) is one of the cornerstones of the country’s security, as well as a large component of the US security role in Asia; approximately 55,000 US troops and other military assets, including aircraft and naval ships, are stationed in Japan and have exclusive use of more than 80 bases and facilities; in exchange for their use, the US guarantees Japan’s security; the Japanese Government provides about $2 billion per year to offset the cost of stationing US forces in Japan; in addition, it pays compensation to localities hosting US troops, rent for bases, and costs for new facilities to support the US presence; Japan also has Major Non-NATO Ally (MNNA) status with the US, a designation under US law that provides foreign partners with certain benefits in the areas of defense trade and security cooperation

Japan was disarmed after its defeat in World War II; shortly after the Korean War began in 1950, US occupation forces in Japan created a 75,000-member lightly armed force called the National Police Reserve; the JSDF was founded in 1954; Article 9 of Japan’s 1947 constitution renounced the use of force as a means of settling international disputes; however, Japan has interpreted Article 9 to mean that it can maintain a military for national defense purposes and, since 1991, has allowed the JSDF to participate in noncombat roles overseas in a number of UN peacekeeping missions and in the US-led coalition in Iraq; in 2014-2015, the Japanese Government reinterpreted the constitution as allowing for "collective self-defense," described as the use of force on others’ behalf if Japan’s security was threatened; in 2022, the government released three security policy documents that labeled China as an “unprecedented strategic challenge,” declared Japan’s intention to develop "counterstrike” capabilities, including cruise missiles and armed drones, and outlined plans to increase Japan’s security-related expenditures to 2% of its national gross domestic product (GDP), in line with NATO standards; post-war Japan generally has limited defense spending to 1% of its GDP (2023)