Second Army, American Expeditionary Forces (AEF), was established in October 1918 during World War I and demobilized in April 1919.

Eager to maintain a hard-fought momentum to drive the Germans out of France, on 10 October 1918, General John J.

Bullard, a Spanish–American War veteran, earned Pershing's confidence and reputation as an aggressive commander, after leading the 1st Infantry Division during the battle of Cantigny.

Bullard's orders for Second Army were to hold the line on a portion of the St. Mihiel sector along the Lorraine front.

Encountering stubborn resistance, Second Army made a considerable advance, recovering a total of approximately 25 square miles of French territory before the armistice terminated hostilities on 11 November.

During its first month of combat operations, 102 soldiers serving under Second Army earned the Distinguished Service Cross.

After the armistice, Second Army occupied an area in Belgium and Luxembourg, remaining there until the end of March 1919, and demobilized in France on 15 April 1919.

The Second Army was authorized by the National Defense Act of 1920 and was originally to be composed of units primarily from the Fourth, Fifth, and Sixth Corps Areas.

The Second Army's mission was to develop defense and operational plans for contingencies near the Great Lakes and the north-central United States, review the mobilization plans of the Fifth and Sixth Corps Areas, and oversee the training of units in the Army area.

As part of the responsibility to oversee training, the Second Army staff planned, conducted, and/or participated in three major maneuvers between 1936 and 1941.

The next Second Army maneuver was also a split exercise, this time under the command of Lieutenant General Stanley H. Ford.

To have more efficient command and control of the Second Army’s subordinate units, then mobilizing and concentrating in Missouri, Arkansas, and Louisiana, Lieutenant General Ben Lear moved the army headquarters to 44 South Second Street, Memphis, Tennessee, on 5 December 1940.

These maneuvers were designed to test and validate a myriad of doctrinal and organizational ideas, and to provide a basis for modernizing the U.S. Army.

During World War II, Second Army trained 11 corps, 55 divisions, and 2,000 smaller units of all arms and services, totaling almost a million men, for employment in all theaters of operation.

[3] A 2017 reorganization eliminated the need for Second Army's network operations coordinating function, and the unit was inactivated on 31 March 2017.