I Corps is designated as one of the active Army's contingency corps. I Corps stays prepared to deploy on short notice worldwide to command up to 5 divisions or a joint task force. I Corps also commands most Army units at Joint Base Lewis-McChord and conducts planning and liaison with other assigned active and Reserve component units located in the continental United States. I Corps is now able to deploy on short notice with both Active Army and Reserve Component forces. Also, at the direction of the Secretary of Defense via the Commander in Chief, Pacific Command, I Corps can activate a joint task force headquarters, Joint Task Force 501 (JTF-501), to respond to regional contingencies.
I Corps was first organized between 15 and 20 January 1918 in the Regular Army in France as Headquarters, I Army Corps at Neufchateau, France. After participating in World War I, I Corps was demobilized on 25 March 1919 in France.
The Corps was reconstituted on 27 June 1944 in the Regular Army as Headquarters, I Corps. Its lineage and honors were consolidated with the active I Corps, which had been constituted first on 15 August 1927 in the Regular Army as Headquarters, XX Corps, and had been serving in the Pacific Theater since the beginning of World War II. The unit continued to serve in the Pacific, eventually becoming part of US occupation forces in Japan. I Corps was inactivated on 28 March 1950 in Japan.
I Corps was reactivated on 2 August 1950 at Fort Bragg, North Carolina. It was subsequently deployed to Korea to assume control of units along the so-called Pusan Perimeter. After the Armistice in 1953, I Corps remained in Korea until 1971, at which time it was reduced to zero strength, remaining on the active rolls, but effectively inactivated. By 1982, the Third Republic of Korea Army had completely taken control of the area of responsibility formerly held by I Corps.
In 1980, Fort Lewis, Washington had been notified of a major change of structure. A corps headquarters was to be activated there in March 1982. I Corps formally uncased its colors at Fort Lewis on 1 October 1981, much earlier than expected. It became a primary contingency planner for US interests in the Pacific region, with a rapidly expanding role in Army affairs.
On 1 August 1983, the Corps expanded its operational control of active Army units outside Fort Lewis, to include the 7th Infantry Division (Light) at Fort Ord, California, and the 172nd Infantry Brigade (Light) in Alaska, which was subsequently tranformed into an element of the 6th Infantry Division (Light).
Between 1980 and 1987, the 9th Infantry Division also evolved at Fort Lewis, Washington. At first called a High Technology Light Division, it was equipped with modified and armed dune buggies and many other items of innovative equipment. Later, the dune buggies were replaced with the High Mobility Multi-purpose Wheeled Vehicles, which carried tank-attack missiles. At about this time, the 9th Division's designation changed from light to motorized. The beginning of the inactivation process for 9th Infantry Division (Motorized) began when it was reduced by one brigade "slice" in the summer of 1988, and the civilian workforce was reduced by some 500 positions, both as economy measures.
Fort Lewis itself continued to grow and modernize during the 1980s. In 1987, two new units were activated at Fort Lewis, the 66th Aviation Brigade and the 201st Military Intelligence Brigade, the latter of which was assigned to I Corps.
During 1989-90, it became obvious that the Cold War had been won. That, combined with national budgetary problems, dictated a careful restructuring of national priorities and of the defense establishment. As these actions evolved, it became evident that Fort Lewis was ideally located to act as a base for mobilization and power projections into the Pacific region. Thus, while most of the Army was downsizing, Fort Lewis began to grow.
In 1990, Fort Lewis received word that it would likely become the home of the 7th Infantry Division (Light) if Congress approved the closure of Fort Ord, California. On 13 September 1990, the 1st Personnel Group was activated at Fort Lewis. The Group Commander was dual-hatted as I Corps Adjutant General and 1st Personnel Group Commander. Also in 1990, the US intervened in the Middle East with Operation Desert Shield. During that intervention, Fort Lewis shipped 34 active and 25 reserve component units to Saudi Arabia and welcomed them home again. I Corps also contributed to the command structure, with the I Corps Commander, Lieutenant General Calvin A. H. Waller and the Deputy I Corps Commander, Major General Paul R. Schwartz, assisting General H. Norman Schwarzkopf, the Commander of the American Forces. I Corps expanded its contingency missions and became a quick-response corps. For several months, I Corps was the nation's worldwide contingency corps, while the XVIII Airborne Corps was in Southwest Asia. This caused a good deal of activity on Fort Lewis, as the post postured itself to support the Corps' expanded mission, and to insure that the Corps had a smooth, rapid departure in case they were needed anywhere in the world.
Also, as a result of units being deployed to Southwest Asia from Fort Bragg, North Carolina, and Fort Riley, Kansas, which were normal ROTC summer camp sites, Fort Lewis became host to the only ROTC summer camp as of 1991. From June through August 1991, approximately 5,300 cadets train at Fort Lewis.
After the return of forces from Southwest Asia, activity on Fort Lewis did not return to pre-war levels. While I Corps did not retain the worldwide contingency mission, it did retain contingency responsibilities for that half of the world whose shores were washed by the Pacific Ocean. The Corps began to convert to a permanently structured, no-mobilization contingency corps and was placed under the operational control of the Commanding General, US Army Pacific Command (USARPAC). This entailed the addition of a number of active component corps units.
This included the approval of the rebasing of the 7th Infantry Division in 1991. Also, by 11 December 1991, inactivation of the 9th Infantry Division was complete. The 3rd Brigade, 9th Infantry Division was reflagged as 199th Infantry Brigade (Motorized). This one-of-a-kind unit was an I Corps unit until it was reflagged as the 2nd Armored Cavalry Regiment (Light), and departed for Fort Polk, Louisiana in 1993.
In preparation for the new I Corps requirements, Fort Lewis began to receive new corps support units which were coming out of Europe. One of these was the 7th Engineer Brigade, which was inactivated on 16 January 1992 and reflagged as the 555th Engineer Group. On 16 February 1992, the 210th Field Artillery Brigade, also from Europe, unfurled its colors at Fort Lewis.
The 7th Infantry Division began preparing for its its move to Fort Lewis in 1992. After beginning the move in March 1993, the decision was made to allow the 1st Brigade, 7th Infantry Division (the 9th Infantry Regiment) to complete moving to Fort Lewis, but to inactivate the rest of the Division. Later in 1993, the post was alerted to expect to receive at least one armored brigade from Europe.
In 1994, Fort Lewis completed an Environmental Impact statement to allow up to 2 heavy brigades to be stationed there, in addition to the 9th Infantry Regiment. In May 1994, elements of the 3rd Brigade, 1st Armor Division began to flow in, and by 1 October 1994, some 3,600 Soldiers and their dependants had arrived. On 29 September 1994, the Brigade was reflagged as the 3rd Brigade, 2nd Infantry Division (Mechanized). The 2nd Division Headquarters and the other 2 brigades remained in Korea.
During 1990s, designated an early deploying corps for military contingencies in the Pacific, I Corps was able to deploy on short notice with both Active Army and Reserve Component forces. I Corps was a contingency force with active, reserve and national guard units in 47 out of 50 states. One brigade out of the I Corps forces, usually drawn from the 25th Infantry Division or 172nd Infantry Brigade, was assigned as the "Division Ready Brigade" for Pacific contigencies, and was available within 48 hours of alert by air transport.
I Corps was unique among the 3 continental United States Corps in that it had no assigned active Army divisions in peacetime and was composed of a balance of Active and Reserve base units in peacetime and wartime. It was further unique in that it was under the Combatant Command of US Pacific Command and under the Operational Control of US Army Pacific. As it was CONUS-based, it relied on US Army Forces Command (FORSCOM) for Title 10 US Code support, or in Joint terminology, was Administratively Controlled to Forces Command.
War plans for I Corps included the Defense of Korea or the Defense of Japan. As a US PACOM major operational headquarters, I Corps was designated by CINCPAC as a standing Joint Task Force (JTF) for theater-wide contingencies. The other primary PACOM standing JTF's were 7th Fleet in Yokosuka, Japan, and III MEF in Okinawa, Japan. Thus, I Corps' readiness responsibilities range from conventional corps roles in a medium-intensity conflict to a full spectrum of missions as a USPACOM JTF.
I Corps base units included approximately 20,000 active-duty soldiers at Fort Lewis, Washington, and an equal number of US Army Reserve and National Guard soldiers based in many of the 50 states. Thus I Corps' name, "America's Corps!" While I Corps was not directly responsible for the readiness of the reserve component units, it did coordinate with the US Army Reserve Command and the states' Adjutant Generals to articulate the wartime requirements and anticipated missions for these Corps base units.
Many of these Reserve Component units participated in I Corps' exercises in CONUS and overseas, including exercises in Japan and Thailand. I Corps' Reserve Component units participated in Operations Joint Guard and Able Sentry. I Corps was at the forefront of the integration of Active Component and Reserve Component units. The military intelligence brigade and engineer group each contained organic Reserve Component subordinate units. It was one of 2 organizations in America's Army sponsoring the Integrated Infantry Battalion Experiment, which would test the ability of integrated Active Component and Reserve Component combat arms units to train and deploy on operational missions. I Corps also worked hard to maintain good relationships with the geographically proximate Pacific Northwest enhanced separate brigades from Washington and Oregon.
I Corps served as AC associate/senior mentor and retains responsibilities for the following corps base units: HHC, 311th Corps Support Command; HHC, 35th Engineer Brigade; HHB, I Corps Artillery; HHC, 66th Aviation Brigade; HHC, 142nd Signal Brigade; HHC, 464th Chemical Brigade; HHC, 326th Finance Group; 82nd Headquarters Detachment, RTOC; HHC, 177th Military Police Brigade; HHC, 364th Civil Affairs Brigade; and HHC, 426th Medical Brigade.
On 12 October 1999, General Eric K. Shinseki, Chief of Staff, Army, announced the acceleration of Army transformation and the creation of 2 medium-weight, Initial Brigade Combat Teams (IBCT) at Fort Lewis, Washington. The 3rd Brigade, 2nd Infantry Division (Heavy) was named to transform first, with the 1st Brigade, 25th Infantry Division (Light) following shortly after. After the 2nd Cavalry Regiment transferred back to Fort Lewis in 2005 from Fort Polk, Louisiana, it became the third unit at Fort Lewis to undergo the the transformation. This concept entailed that the brigades would use lighter weight armored vehicles, dismounted infantry/combined arms, then recent technological developments (particularly in communications and computers), and parallel and collaborative leadership techniques to create a new combat power. The brigades would be deployable anywhere in the world within 96 hours of initial notification. The SBCT combat power would be optimized for Small-Scale Contingencies (SSC) in urban and complex terrain, but it would be capable of participating in the full spectrum of operations. This new concept required reorganizing, re-equipping, and retraining Fort Lewis brigades. In the long term, this transformation process was expected to would serve as a model for change in the US Army.
Under a the concept called "corps packaging," all of the National Guard's 8 combat divisions and 15 enhanced separate brigades were to be matched with active-component divisions at the corps level. Army Chief of Staff Gen. Eric K. Shinseki announced this expansion of teaming between active and Guard divisions on 14 September 2000 in a speech to the National Guard Association annual conference in Atlantic City, New Jersey. Under I Corps, California's 40th Infantry Division (Mechanized) was teamed with the Army's 2nd Infantry Division in Korea, while I Corps also included 3 of the Guard's enchanced brigades, the 116th Armored Cavalry Brigade in Idaho, the 29th Infantry Brigade in Hawaii, and Washington's 81st Infantry Brigade.
With the events of 11 September 2001, I Corps entered a new era and century bringing new challenges and requirements. Assets were active in providing support for real world missions on the "Global War on Terrorism" (GWOT) with Operation Enduring Freedom (OEF) in Afghanistan, force protection Operation Noble Eagle (ONE) and Operation Iraqi Freedom (OIF) in Iraq. I Corps implemented a persistent individual Soldier readiness training and exercise schedule. An aggressive acceleration of the swiftest deployability dates of the new Stryker Brigade Combat Teams was also employed.
During March and April 2003, 3rd Brigade Combat Team, 2nd Infantry Division traveled to the National Training Center (NTC) in Fort Irwin, California and participated in an exercise dubbed Arrowhead Lightning I. After completion of its NTC rotation, its Stryker Combat Vehicles and other equipment were moved by land, sea, air, and rail to Fort Polk, Louisiana for Arrowhead Lightning II. In May 2003, the 3rd Brigade Combat Team, 2nd Infantry Division completed a Certification Exercise (CERTEX) at the Joint Readiness Training Center (JRTC) where it validated the Stryker vehicle concept to be a viable one. In November 2003, it became the first Stryker Brigade deployed for combat operations in support of the Global War on Terrorism (GWOT). The Arrowhead Brigade returned to Fort Lewis in November 2004 after a very successful rotation to OIF and was replaced by another Stryker Brigade Combat Team, the 1st Brigade Combat Team, 25th Infantry Division. In June 2006, the 3rd Brigade Combat Team, 2nd Infantry Division left for a second year-long deployment in Iraq. Also in June 2006, the newly formed 4th Brigade Combat Team, 2d Infantry Division stood up as the next brigade to undergo Stryker validation training.
The date 4 February 2004, marked the first time that I Corps command elements forward deployed in combat since the end of the Korean War. Task Force Olympia deployed to Mosul, in northern Iraq in January 2004, where it assumed its mission from the 101st Airborne Division to form a headquarters to exercise command and control of all coalition and Iraqi forces in northern Iraq. Task Force Olympia included representatives from all 3 components of the US Army (Active, Reserve and National guard), as well as US Marine Corps and Australian officers. The headquarters coordinated the efforts of both of the the Army's first 2 Stryker Brigade Combat Teams, attached engineers, civil affairs, signal, and other supporting units as well as, ultimately, more than 12,000 Iraqi security forces. The Iraqi security forces included 4 Civil Defense Corps battalions, 3 Border Police battalions, several thousand members of the Iraq Facility Protection Security Forces and an Armed Forces battalion. After more than a year in Iraq, Task Force Olympia handed over responsibility for northern Iraq to the Soldiers of Task Force Freedom and 11th Armored Cavalry Regiment in February 2005.
The Total Army Analysis (TAA) was a biennial, multiphased force-structuring process that generated the tactical support forces and general purpose forces necessary to support divisional and non-divisional combat forces in executing the national strategy, given resource constraints and end-strength guidance. The TAA-05 confirmed the 111th Air Defense Artillery Brigade missioning to I Corps.
The transformation of the US Army to the modular force structure, beginning in 2004-2005, greatly affected the structure of I Corps. The changes in the relationships between active and reserve component units and the brigade-centric deployment focus meant that I Corps reserve component units directly assigned to it were replaced with active component units. I Corps remained one of 4 corps headquarters in the active Army, and one of 3 based in the continental United States. I Corps remained under the administrative control of FORSCOM.
In late 2004, the 1st Military Police Brigade (Provisional) was inactivated and reflagged as the 42nd Military Police Brigade, which was assigned to I Corps. The 555th Engineer Group was also provisionally redesignated by US Army Forces Command (FORSCOM) as the 555th Combat Support Brigade (Maneuver Enhancement) after returing from a deployment in support of Operation Iraqi Freedom in late 2004.
In 2006, the 1st Brigade Combat Team, 25th Infantry Division was inactivated and reflagged as the 2nd Armored Cavalry Regiment. The 2nd Armored Cavalry Regiment was inactivated and reflagged as the 4th Brigade Combat Team, 2nd Infantry Division. This reorganization saw the 25th Infantry Division assigned completely to US Army Pacific, with units in Hawaii and Alaska. The 2nd Infantry Division was to be assigned to I Corps, with the exception of the 1st Brigade Combat Team, 2nd Infantry Division in Korea, remaining assigned to Eighth US Army. 2nd Brigade Combat Team, 2nd Infantry Division returned to CONUS in 2006 following a deployment to Operation Iraqi Freedom, and was subsequently inactivated at Fort Carson, Colorado. During this period, the 1st Personnel Group was also inactivated.
The 5th Brigade Combat Team, 2nd Infantry Division was activated as part of I Corps in 2007. Also in 2007, a forward deployed element of I Corps, I Corps (Forward) was activated at Camp Zama in Japan. This unit was formed into a merged command with US Army Japan. The 555th Engineer Group was formally reorganized and redesignated as a modular engineer brigade in June 2007. In July 2007, the 17th Field Artillery Brigade was tranformed into a modular fires brigade and assigned to I Corps.
In April 2008, the 593rd Corps Support Group was reorganized and redesignated as the 593rd Sustainment Brigade, remaining assinged to I Corps. In July 2008, the 201st Military Intelligence Brigade also began transforming to a modular battlefield surveillance brigade. In September 2008, I Corps Artillery, part of the Utah National Guard, was formally inactivated.
In July 2010, 5th Brigade Combat Team, 2nd Infantry Division was inactivated and reflagged as the 2nd Brigade Combat Team, 2nd Infantry Division.
In March 2011, the Department of Defense announced the movement of 16th Combat Aviation Brigade headquarters from Fort Wainwright, Alaska, to Joint Base Lewis-McChord, Washington. This would realign the 16th Combat Aviation Brigade with I Corps, though the 1st Battalion, 52nd Aviation and 6th Squadron, 17th Cavalry would remain in Alaska to support USARAK. On 15 June 2011, the 16th Combat Aviation Brigade cased their colors at Fort Wainwright, Alaska and moved the Headquarters and Headquarters Company to Joint Base Lewis-McChord, Washington. On 1 August 2011, the 16th Combat Aviation Brigade completed its move to Joint Base Lewis-McChord during a ceremony at Gray Army Airfield in which it uncased its colors. At that time it formally became part of I Corps and was also expanded to include 2 newly activated units, as well as previously activated units such as 4th Squadron, 6th Cavalry.
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