First Army Division West The First Army Division West is a division of the First United States Army . With its new role , the First United States Army developed two subordinate multi - component headquarters – one division to support the western United States and the other to support the eastern United States . First Army Division East was activated at Fort Meade , Maryland . First Army Division West was activated on March 7 , 2007 , and is headquartered at Fort Hood , Texas . First Army Division West was established by the Department of the Army to provide training and readiness oversight and mobilization operations for an area of responsibility spanning the states and territories west of the Mississippi River . First Army Division West is responsible for mobilizing , training , readiness oversight and deploying the United States ' Reserve Component and National Guard Soldiers , and selected Sailors and Airmen along with members of multiple interagency and governmental entities . The division is organized into eight brigades located throughout the western United States with 52 total battalions . First Army Division West is responsible for the following eight brigades . History . The First United States Army was activated in France on Aug . 10 , 1918 , under the command of Gen . John J . Pershing . As America ’ s first numbered army , First Army engaged in two major operations – the reduction of the St . Mihiel Salient , east of Verdun , and the great Meuse - Argonne offensive , west of Verdun . After World War I ended and after a short period of occupation in Europe , First Army was deactivated in 1919 . Reactivated at Fort Jay , N . Y . in 1933 , First Army ’ s new mission of training and readiness matched today ’ s mission . On D - Day , June 6 , 1944 , with Gen . Omar N . Bradley commanding , First Army ’ s troops landed on Omaha and Utah beaches in Normandy . First Army established an impressive record of ‘ firsts ’ in World War II including first on beaches of Normandy and first into Paris . After World War II , First U . S . Army headquarters was on Governor ’ s Island , N . Y . On Jan . 1 , 1966 , First and Second Armies merged and First Army headquarters moved to Fort George G . Meade , Md . In 1973 , First Army transitioned from an active army organization to one dedicated to improving the readiness of the Reserve Components . Once again , in 1983 , reorganization took place . Second U . S . Army was reactivated at Fort Gillem , Ga . , and assumed responsibility for Reserve Component matters in seven states and two territories formerly belonging to First Army . In 1991 , Fourth U . S . Army was deactivated and its seven mid - western states became part of First Army . In 1995 , First Army left Fort Meade , Md . , and was reorganized at Fort Gillem , Ga . , On January 16 , 2006 , First Army ’ s mission expanded to include the training , readiness oversight , and mobilization for all U . S . Army Reserve and Army National Guard units within the continental United States and two U . S . territories . First Army assumed authority from Fifth Army , which was transforming into U . S . Army North – assuming nationwide responsibility for homeland security . With its new role , First Army developed two subordinate multi - component headquarters – one division to support the eastern United States and the other to support the western United States . First Army Division West was activated at Fort Carson , Colo . and moved its headquarters to Fort Hood , Texas in 2009 . First Army Division East was activated on March 7 , 2007 , and is headquartered at Fort George G . Meade , Md . The establishment of Division West eliminated the requirement for the 7th Infantry Division at Fort Carson , which was inactivated in a ceremony at the Mountain Post on August 22 , 2006 .