1861–1865 - Civil War

The Army of Northeastern Virginia was the unofficial name of the Union's primary fighting force in the Eastern Theater of the American Civil War prior to the formation of the Army of the Potomac.

Key facts about the Confederate Army of Northern Virginia.

Organized in 1861, and officially named in 1862, the Army of Northern Virginia was the principal military force of the Confederate States of America in the Eastern Theater of the American Civil War.

Key facts about the American Civil War Confederate Army of Tennessee.

The Army of Tennessee was the Confederacy's primary fighting force in the Western Theater of the American Civil War between 1862 and 1865.

Basic facts about the Union Army of the Border, which battled Major General Sterling Price's Army of Missouri during Price's Missouri Expedition of 1864.

Union Major General Samuel Curtis organized the Army of the Border to confront Confederate Major General Sterling Price's Army of Missouri as it marauded through Missouri during October 1864.

Key facts about the American Civil War Union Army of the Cumberland.

During the American Civil War, the Union Army of the Cumberland participated in nearly all of the major campaigns in the Western Theater.

Key facts about the Union Army of the Frontier.

Formed from forces in the field from Missouri and Kansas the short-lived Army of the Frontier fought to maintain Union control of Missouri during 1862 and 1863.

Key facts about the Union Army of the Gulf.

An amalgamation of troops assigned to the Department of the Gulf from 1862 through 1865, the Army of the Gulf served as an occupation force in New Orleans (1862-1863) and as the main Union command during the Red River Campaign during the American Civil War.

Key facts about the Union Army of the James.

During the American Civil War, Lieutenant General Ulysses S. Grant consolidated troops from the Department of Virginia and North Carolina to form the Army of the James to support his Overland Campaign in 1864.

Key facts about the Confederate Army of the Mississippi.

Officially organized on March 5, 1862, the Army of the Mississippi transitioned into the Army of Tennessee, the Confederacy's preeminent fighting force in the Western Theater of the American Civil War.

Key facts about the Union's first Army of the Mississippi.

Created on February 23, 1862, the Army of the Mississippi participated in the Battle of Island No. 10, the Siege of Corinth, the Battle of Iuka, and the Battle of Corinth II, before being discontinued on October 26, 1862.

Unofficially organized and discontinued in January 1863, the second Army of the Mississippi easily overran Brigadier-General Thomas J. Churchill's Confederate garrison at Fort Hindman during the Battle of Arkansas Post (January 9-11, 1863).