| Unit Name: | United States Army, Japan |
| Dates: | 1 July 1957–present[1] |
| Command Structure: | United States Forces, Japan United States Army Pacific |
| Garrison: | Camp Zama, Japan |
| Motto: | Omnia Fieri Potest |
| Commander1: | Major General David B. Womack |
| Commander1 Label: | Current Commander |
| Notable Commanders: | Roscoe Robinson Jr., James C. Boozer Sr., Viet Xuan Luong |
| Identification Symbol Label: | Distinctive Unit Insignia |
United States Army, Japan (USARJ) is a Major Command of the United States Army. It consists of operating port facilities and a series of logistics installations throughout Honshū and Okinawa. USARJ participates actively with the Japan Ground Self-Defense Force in bilateral training exercises and the development of bilateral plans. It commands and supports United States Army assigned units, attached units, and augmentation forces and employs these forces in support of the commander. USARJ maintains and strengthens the credibility of deterrent power in the Pacific through maintenance of defense facilities, war reserves and operational project stocks. USARJ is headquartered at Camp Zama.
As the Army Component Command to United States Forces Japan (USFJ) and as a Major Subordinate Command of United States Army Pacific (USARPAC), United States Army Japan (USARJ)/I Corps (Forward) is responsible to provide support of Article V (Defense of Japan) and VI (ensuring regional stability) of the U.S.-Japan Mutual Security Treaty. It serves as a forward stationed Army headquarters; supports regional security cooperation activities with the Japan Ground Self Defense Force contributes to the security of Japan and maintenance of peace and security in the Far East; provides communities of excellence and installation operations that support Soldiers, Civilians, and their Families.
The following units make up US Army Japan:[2]
The earliest origins of United States Army Japan can be traced to General Douglas MacArthur's assumption of command of U.S. Army Forces in the Far East. USAFFE was established in Manila in July 1941. The command was destroyed as the U.S. were defeated in the Japanese invasion of the Philippines. Eventually the Army Forces Far East title was resurrected as the land forces element of the Far East Command in Tokyo after the end of the Second World War. When Far East Command was disestablished in 1957, several smaller U.S. Army commands were created.
U.S. Army Japan (USARJ) first appeared on 1 July 1957 as a major subordinate command of United States Army Pacific (USARPAC) in Hawaii. Reorganized again on 1 September 1968, USARJ employed a new structure to maximize operational efficiency while keeping its existing missions and functions.
The reversion of Okinawa to Japanese control on 15 May 1972, resulted in the realignment of the Army's Pacific commands with HQ USARJ absorbing elements for Okinawa, adjusting the command chain. IX Corps was transferred from Okinawa and collocated with this command to become HQ USARJ/IX Corps.
On 1 July 1974, a USARJ reorganization established three subordinate commands: U.S. Army Garrison, Honshu (USAGH); U.S. Army Garrison, Okinawa (USAGO); and the U.S. Army Medical Department Activity-Japan, (MEDDAC-JAPAN). With the discontinuance of USARPAC, USARJ was designated a major Army command on 1 January 1975, reporting directly to Department of the Army.
In August 1990, USARPAC was reestablished and USARJ became a major subordinate command of that headquarters as well as continuing as the Army Component Command of U.S. Forces, Japan (USFJ). In 1994, IX Corps was replaced by 9th Theater Army Area Command and on 8 November 1999, was redesignated 9th Theater Support Command (TSC). There were several minor reorganizations and redesignations over the next decade so that by 11 September 2001, USARJ consisted of logistics bases in Japan and Okinawa.
In September 2007, the 9th TSC was inactivated and on 19 December 2007, I Corps (Forward) was activated in Japan in line with the Army's transformation efforts. USARJ remains headquartered at Camp Zama, where it engages in numerous bilateral activities with the Japan Ground Self-Defense Force (JGSDF) and performs duties as United States Forces Japan's Army Component Command.
Command of the 78th Signal Battalion remained with the Hawaii-based 516th Signal Brigade (formerly 1106th) and operational control remains with the commander, USARJ/9th TAAC and since December 19, 2007, USARJ/I Corps (Forward).[3]
On 11 March 2011, a devastating magnitude 9.0 earthquake and tsunami struck the northeast coast of Japan. Within minutes, USARJ began humanitarian assistance and disaster relief operations in support of the JGSDF during Operation Tomodachi, Japan's largest-ever bilateral operation. USARJ supported the affected people after operations officially ended by providing equipment and maintenance support to the JGSDF until September.