Confederate military organization which existed in three iterations. The first was organized on March 5, 1862, and participated in the battles of Shiloh, Corinth, and Perryville. It was commanded by P. G. T. Beauregard, Albert Sidney Johnston, and Braxton Bragg until its dissolution on November 20, 1862, when Bragg reorganized his forces into the Army of Tennessee.
The second was organized and commanded by John C. Pemberton principally for the defense of Vicksburg, Mississippi, from December 7, 1862, until surrender on July 4, 1863.
The third organization lasted from July 30, 1863, until June 26, 1864, under the command of William J. Hardee, Leonidas Polk, and William Loring, until its eventual absorption into the Army of Tennessee.