The Japan Self-Defense Forces (自衛隊 Jieitai, abbreviated JSDF) is the official military force of Japan. The JSDF was established after World War II, and are notably prohibited from deploying outside of Japanese territory.
Joint Assault universe
The JSDF is first seen in mission 1, "Steel Axe", where they participate with the United States Navy Seventh Fleet and a major private military company called Martinez Security in a joint military show over Midway Island in the Pacific Ocean, and later assist both forces in engaging a Valahia air force heading towards Tokyo, Japan's capital. They are later seen again in "Bird Hunt", where they attempt to defend Tokyo from the invading Valahia fighters and its trump card, the giant combat aircraft Spiridus, and later again in "Red and Black - Alpha/Bravo", where they are assisted by Martinez in fending off enemy forces coming from, respectively, the northern Izu Islands and the southern Boso Peninsula. The Self-Defense Forces make their final appearance in mission 5, "Capital Defense", where they, alongside Martinez Security, defend Tokyo once again from Valahia's assault, this time from the airborne aircraft carrier Orgoi.
Following the Orgoi's destruction in Tokyo, the Valahia retreated from the region, with Martinez and the International Union Peacekeeping Force following suit. Possibly because of their prohibition of waging war outside Japan, the JSDF are not seen again in the story.