When the American Civil War began, the residents of the border state of Missouri had divided sympathies. Although many Missourians favored remaining in the Union, Governor Claiborne Jackson was a strong proponent of secession. Despite his secessionist leanings, Jackson declared his support for the Union and affirmed Missouri’s neutrality by agreeing to terms of the Price-Harney Truce on May 12, 1861. When President Abraham Lincoln requested 75,000 troops from Missouri to take up arms against the Confederacy, Jackson withdrew his support of neutrality. A subsequent meeting between Jackson and Union Brigadier General Nathaniel Lyon did not resolve the matter. Instead, Lyon’s Army of the West and the Missouri State Guard, commanded by former Missouri Governor Sterling Price, engaged in a series of minor battles during the summer of 1861 for control of the state.
Confederates gained the upper hand in August 1861 when their Western Army defeated the Union Army of the West at the Battle of Wilson’s Creek (August 10, 1861). The Rebel victory buoyed secessionist sympathies in Missouri and emboldened the Confederates to launch an offensive to regain control of northern Missouri in March 1862. The Federal Army of the Southwest, however, dashed its ambitions when it defeated the Rebel Army of the West at the Battle of Pea Ridge (March 6–8, 1862). The victory secured Federal control of Missouri, and it enabled the Union to focus on other areas in the Mississippi Valley. For the rest of the war, the preponderance of Union activity in Missouri and most of the Trans-Mississippi region comprised efforts to curtail guerrilla raiders and seditious activities of Confederate sympathizers.
Because of pressing needs in other campaigns east of the Mississippi River, Union officials folded most of Army of the Southwest’s soldiers into the Army of the Tennessee and the Army of the Mississippi during the summer and autumn of 1862. Emboldened by the depletion of Union troops, Confederates again began threatening southwest Missouri. In response, the War Department issued General Orders, No. 135 on September 19, 1862, re-creating the Department of the Missouri under the direction of Major General Samuel R. Curtis, the victorious commander at the Battle of Pea Ridge. A few weeks later, on October 12, 1862, Curtis issued General Orders, No. 7 (Department of the Missouri) appointing Brigadier General John M. Schofield to command roughly 15,000 soldiers, “denominated the Army of the Frontier” operating in the department. Although Schofield technically was not eligible to lead a full army at the time due to his rank, Curtis felt comfortable in selecting him because his confirmation as a major general was pending in the U.S. Senate.
Battle of Clark’s Mill
Schofield spent his first weeks as commander of the Army of the Frontier trying to curb the growing number of Confederate insurgents in Southern Missouri—not always successfully. On November 7, 1862, a Rebel cavalry force of roughly 1,000 troopers forced 100 of Schofield’s soldiers to surrender following a skirmish known as the Battle of Clark’s Mill in Douglas County.
Union Victories at Cane Hill, Prairie Grove, and Van Buren
Two weeks after the loss, Schofield temporarily turned over his command to Brigadier General James G. Blunt on November 20, 1862, because of illness. A week later, Blunt moved 5,000 of his men into Northwest Arkansas to check a Confederate force headed toward Southern Missouri. Blunt’s men successfully scattered the Rebel force at the Battle of Cane Hill on November 28, 1862. The Union general followed his victory by forcing the Confederates to retreat farther south after the Battle of Prairie Grove on December 7, 1862. Three weeks later, the men of the Army of the Frontier secured Union control of Northwest Arkansas by defeating the First Corps of the Trans-Mississippi Army at the Battle of Van Buren on December 28, 1862.
The day after the Union victory at the Battle of Van Buren, Schofield returned to Southern Missouri and resumed command of the Army of the Frontier, on December 29, 1862. A few months later the Senate refused to confirm Schofield’s appointment as a major general, thus rendering him ineligible to lead an army. Meanwhile, because of the Union victories at Cane Hill, Prairie Grove, and Van Buren, on January 22, 1863, the Senate confirmed Schofield’s subordinates, Blunt and Francis J. Herron as major generals, effective November 29, 1862. The two confirmations created the awkward situation of two major generals serving under a brigadier general who was not eligible to command an army. Curtis resolved the issue on March 30, 1863, when he issued General Orders, No. 24 (Department of the Missouri) appointing the recently confirmed Herron to command the Army of the Frontier. The War Department, meanwhile, ordered Schofield to report to Major General William S. Rosecrans and the Army of the Cumberland and assigned him to command the Third Division of the Fourteenth Corps, under the command of Major General George H. Thomas.
Battle of Chalk Bluff
Herron assumed command of the Army of the Frontier on April 1, 1863. A month later on May 1-2, the army’s Second Division, commanded by Brigadier General William Vandever, inflicted heavy casualties on a Rebel force at the Battle of Chalk Bluff, Arkansas. The strategic Union victory thwarted another Confederate attempt to invade Missouri.
On May 12, 1863, President Lincoln renominated Schofield for promotion to major general. The next day, the War Department assigned Schofield to replace Curtis as commander of the Department of the Missouri. Three weeks later, on June 2, General-in-Chief Henry W. Halleck requested Schofield to send troops to Mississippi and Tennessee to support Major General Ulysses S. Grant’s campaign to subdue Vicksburg.
In June, Schofield complied by ordering Herron west, along with the 2nd and 3rd divisions of the Army of the Frontier. Upon his arrival, Herron’s two divisions were consolidated to form “Herron’s Division” of the 17th Army Corps during the rest of the Vicksburg Campaign. After the fall of the Vicksburg, army officials attached Herron’s men to the 13th Army Corps commanded by Major General Edward Ord.
On August 14, 1863, Ord issued General Orders, No. 24 (13th Army Corps) announcing that “The division known as the Army of the Frontier, Major General F. J. Herron commanding, will henceforth be known as the Second Division Thirteenth Army Corps.” Back in Missouri, the remnants of the Army of the Frontier continued to campaign under Blunt’s command against guerrillas until October 19, 1863, when Schofield issued General Orders, No. 118 reorganizing the department ending the existence of the Army of the Frontier.