U.S. Forces Japan (USFJ) is a joint military command of the United States Armed Forces stationed in Japan. Established after World War II, its primary mission is to ensure the security of Japan and maintain regional stability in East Asia. USFJ operates under the U.S.-Japan Security Treaty, which allows American troops to be stationed in Japan. The forces include various branches, such as the U.S. Army, U.S. Navy, U.S. Air Force, and U.S. Marine Corps. They conduct training exercises, humanitarian missions, and disaster response operations. USFJ plays a crucial role in the defense strategy of both the U.S. and Japan.