First Army (United States)

First Army is the oldest and longest-established field army of the United States Army. It served as a theater army, having seen service in both World War I and World War II, and supplied the US army with soldiers and equipment during the Korean War and the Vietnam War under some of the most famous and distinguished officers of the U.S. Army. It now serves as a mobilization, readiness and training command.

The First Army was established on 10 August 1918 as a field army when sufficient American military manpower had arrived on the Western Front during the final months of World War I. The large number of troops assigned to the American Expeditionary Forces (AEF) required the activation of subordinate commands. To fill this need, First Army was the first of three field armies established under the AEF. The first commander was General John J. Pershing, who also served as Commander-in-Chief (C-in-C) of the AEF. The headquarters planned and directed the first major American offensive, the St Mihiel Offensive (September 12 to 16, 1918). It later went on to fight in the largest and deadliest battle in the United States Army's history, the Meuse–Argonne offensive. Serving in its ranks throughout World War I were many figures who later played important roles in World War II. First Army, now under Lieutenant General Hunter Liggett, was inactivated on April 20, 1919, five months after the Armistice with Germany which ended hostilities.

As part of the realization of the 1920 amendment to the National Defense Act of 1916, the Army Chief of Staff, General Douglas MacArthur, directed the establishment of six field armies that each commanded three corps areas that were geographically located. The "First Army Area" (First, Second, and Third Corps Areas) contained the First and Fourth Armies, the "Second Army Area" (Fourth, Fifth, and Sixth Corps Areas) contained the Second and Fifth Armies, and the "Third Army Area" (Seventh, Eighth, and Ninth Corps Areas) contained the Third and Sixth Armies. Between 1921 and 1932, the six field armies were constituted in the Organized Reserve rather than in the Regular Army, as the War Department did not see a need for active-duty field army headquarters in peacetime. The Headquarters and Headquarters Company, First Army, was originally constituted in the Organized Reserve on 15 October 1921 and allotted to the Second Corps Area. The headquarters was initiated on 28 August 1924 at New York City, New York. In August 1927, the War Department realized it would need at least one active-duty field army, in command of three corps, in case of any contingencies, and so the First Army was withdrawn from the Organized Reserve on 15 August 1927 and demobilized.

A new field army, designated Headquarters and Headquarters Company, Seventh Army, was constituted in the Regular Army on 15 August 1927 and allotted to the Second Corps Area in place of First Army. It was redesignated Headquarters and Headquarters Company, First Army on 13 October 1927. Headquarters, First Army, was activated on 8 September 1932 at Governor’s Island, New York, and assumed control over the First, Second, and Third Corps Areas. The First Corps Area was headquartered in Boston, Massachusetts, Second Corps Area was headquartered at Fort Jay, on Governors Island in New York Harbor, and Third Corps Area headquarters was at Fort Howard near Baltimore, Maryland. The overall mission of First Army was commanding and training the Regular Army, National Guard, and Organized Reserve units in its three corps areas.

First Army's first commander, from 1932 to 1936, was Major General Dennis E. Nolan, who had been the American Expeditionary Force's (AEF) chief of intelligence during World War I. He was followed by Major General Fox Conner, previously First Corps Area commander, who had been the AEF's Chief of Operations in World War I. In the years between the wars, Conner was a crucial mentor in the careers of Dwight Eisenhower and George C. Marshall. Passed over as a candidate for Army Chief of Staff for Douglas MacArthur in 1930, Conner was assigned to command the First Corps Area instead, later commanding First Army in 1936. Conner retired in 1938.

In 1938, First Army came under command of General Hugh A. Drum. Drum began to develop the First Army into a bona fide field army with the expansion of the Army in 1939 and through the early 1940s. It began to establish and develop its own staff and participated in the large-scale Army maneuvers in Louisiana and North Carolina between 1939 and 1941. As the United States entered World War II, Drum was assigned command of the newly established Eastern Defense Command, responsible for coastal and domestic defense, which relieved the First Army of this responsibility on 24 December 1942. Drum retired in 1943 when he reached the mandatory retirement age. General George Grunert, commander of the Second Service Command, assumed command of the First Army until Headquarters, First Army was activated in Bristol, England in January 1944 under the command of General Omar Bradley.

First Army's entry into World War II began in October 1943 as Bradley returned to Washington, D.C., to receive his command and began to assemble a staff and headquarters to prepare for Operation Overlord, the codename assigned to the establishment of a large-scale lodgement on the European Continent following Operation Neptune, which was the invasion of Normandy. The headquarters were activated in January 1944 at Bristol, England.

The second iteration of the First Army as constituted in the Regular Army after World War I did not continue the lineage of the World War I-era First Army; on 27 June 1944, the World War I-era First Army was reconstituted in the Regular Army as Headquarters and Headquarters Company, First Army, and was consolidated with the active Headquarters and Headquarters Company, First Army. Upon going ashore on 6 June 1944, D-Day, First Army came under General Bernard Montgomery's 21st Army Group (alongside the British Second Army) which commanded all American ground forces during the invasion. Three American divisions were landed by sea at the western end of the beaches, and two more were landed by air. On Utah Beach, the assault troops of VII Corps made good progress, but V Corps on Omaha Beach came nearest of all of the five landing areas to disaster. The two American airborne divisions that landed, the 82nd and 101st, were scattered all over the landscape, and caused considerable confusion among the German soldiers, as well as largely securing their objectives, albeit with units completely mixed up with each other. First Army captured much of the early gains of the Allied forces in Normandy. Once the beachheads were linked together, its troops struck west and isolated the Cotentin Peninsula, and then captured Cherbourg. When the American Mulberry harbour was wrecked by a storm, Cherbourg became even more vital.