Army of the Mississippi
In 1863 Major general John Alexander McClernand was put in command of the expedition against the Confederates down the Mississippi.  He was given command of two corps from the Army of the Tennessee. McClernand named his force the "Army of the Mississippi". McClernand was successful in capturing Arkansas Post but he acted without orders. On January 30, 1863, Grant personally took command of the army. The old XIII Corps and XV Corps were returned to the Army of the Tennessee on January 12, 1863.