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).
Organization of the Army
On October 16, 1862, the U.S. War Department issued General Orders No. 159, placing Major General Ulysses S. Grant in command of the newly created Department of the Tennessee. On October 26, one day after assuming his new position, Grant issued General Orders No. 2, Department of the Tennessee, stating, “The army heretofore known as the ‘Army of the Mississippi,’ being now divided and in different Departments, will be discontinued as a separate Army.” A little over two months later, a second Army of the Mississippi would briefly materialize under the leadership of Major General John A. McClernand.
McClernand was a Democratic politician from Southern Illinois who raised a brigade of volunteers at the beginning of the Civil War and served under Grant during the early Union victories in Tennessee. McClernand was also an ambitious man, who was well-connected with fellow Illinoisan and President Abraham Lincoln. Chafing under Grant’s leadership, McClernand visited Lincoln in Washington, D.C., in October 1862 to lobby for an independent command. Wishing to maintain the support of Illinois Democrats, Lincoln acquiesced to McClernand’s appeals. Secretary of War Edwin M. Stanton allowed McClernand to return to Illinois to raise troops for an assault on the Confederate stronghold of Vicksburg, Mississippi. On December 18, 1862, Stanton issued General Orders No. 210, placing McClernand in charge of the newly created 13th Army Corps.
Before McClernand finished his recruiting assignment, Grant began his own Vicksburg Campaign. In December, Grant ordered William T. Sherman to lead over 30,000 Federal soldiers down the Mississippi River, disembark near the mouth of the Yazoo River, and to attack Vicksburg from the north. Fewer than 6,000 Confederate defenders easily repulsed Sherman’s assault at the Battle of Chickasaw Bayou (December 26 to 29, 1862), forcing the Federals to withdraw.
Battle of Arkansas Post
In early January, McClernand arrived at the mouth of the Yazoo River with the corps he had recruited. Stanton authorized McClernand (who was senior to Sherman) to combine his 13th Corps with Sherman’s 15th Corps and to begin an assault on Vicksburg. McClernand unofficially renamed his combined force the Army of the Mississippi and attacked Fort Hindman, near Arkansas Post, rather than to assault Vicksburg, as expected. McClernand’s 33,000-man army easily overran Brigadier-General Thomas J. Churchill’s 5,500-man garrison at Fort Hindman during the Battle of Arkansas Post (January 9–11, 1863). The Union victory contributed little toward the success of the Vicksburg Campaign, but it eliminated a minor impediment to Union shipping on the Mississippi River.
Dissolution of the Army
Flushed with success and eager for glory, McClernand announced an expedition against the Arkansas capital at Little Rock. Grant, however, was unimpressed with McClernand’s victory and considered it a diversion from the real task at hand. On January 30, 1863, Grant took control of Union forces operating near Vicksburg. He countermanded McClernand’s plans to attack Little Rock and ordered him to rejoin the Union campaign against Vicksburg. Grant then relegated McClernand to his former position as commander of the 13th Corps, thus ending the unofficial existence of the second Army of the Mississippi.