December 25, 1861 – December 13, 1862
The Army of the Southwest was a short-lived Union force organized on December 25, 1861, to resist Confederate forces operating in Missouri.
When the American Civil War began, sympathies in the border state of Missouri were greatly divided. 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 failed to 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.
By mid-July, Lyon's army had driven Price's forces into the southwestern corner of Missouri, where they received reinforcements from other southern states. Brigadier General Ben McCulloch commanded the newly-formed combined Confederate force. Rather than stand by and watch McCulloch's army continue to grow, Lyon determined to go on the offensive. On August 9, 1861, he led about 5,400 Union soldiers out of Springfield to assault over 11,000 Rebels encamped near Wilson's Creek, approximately twelve miles southwest of the city.
Lyon surprised the Confederates with an attack on the morning of August 10 near Wilson's Creek. During a hard day of fighting, Lyon was killed, and the Federals exhausted their ammunition, forcing them to abandon the assault. The Rebels were too spent to pursue. Control of Missouri was still undecided.
After the Battle of Wilson's Creek, discord between McCulloch and Price resulted in the former moving back into Arkansas, while the latter continued operations in Missouri. President Jefferson Davis intervened, seeking to settle the differences between McCulloch and Price and to coordinate operations west of the Mississippi by creating the Trans-Mississippi District. In January 1862, Davis appointed Major General Earl Van Dorn to command the new district. On January 29, Van Dorn assumed command, established his headquarters at Pocahontas, Arkansas, and began the task of organizing his forces.
On the Union side, things were also in disarray after the Battle of Wilson's Creek. Ineffectual leadership had plagued the Western District. Seeking more stability, in November 1861, the Lincoln administration appointed Major General Henry W. Halleck, who was noted for his organizational skills, to command the district. On December 25, Halleck appointed Brigadier General Samuel R. Curtis to command the Southwestern District of Missouri (Special Orders, No. 92, Department of the Missouri). The troops under Curtis' command came to be known as the Army of the Southwest.
Halleck's selection of Curtis was controversial because many of the residents and volunteers in the Western District were German Americans who preferred Brigadier General Franz Sigel who shared their ethnicity. Nonetheless, Halleck was skeptical of Sigel's leadership abilities after the latter's performance at Wilson's Creek. When Sigel learned that he had been passed over, he wrote to Curtis on December 26, 1861, threatening to resign. Sigel's complaints became a cause célèbre amongst German-Americans that eventually reached the national press, the halls of Congress, and President Lincoln's office. After several weeks of backroom negotiations, the matter was defused when Halleck and Curtis organized the Army of the Southwest along ethnic lines, giving Sigel overall command of the 1st and 2nd Divisions, commanded respectively by Colonel Peter J. Osterhaus and Brigadier General Alexander Asboth. Brigadier General Jefferson C. Davis commanded the 3rd Division, which was manned by native-born Americans.
Eager for action after assuming command of the Army of the Southwest, Curtis struck out after Price in January 1862 and quickly drove him out of Missouri, into Arkansas. By February, Curtis crossed into Arkansas but had to halt his pursuit because his supply lines could not support farther advancement. Not wanting to retreat, he established a base along Little Sugar Creek, just south of a hostelry named Elkhorn Tavern, and began foraging operations.
Meanwhile, Van Dorn developed ambitious plans to sweep through Missouri, to capture St. Louis, and to threaten Union operations in Kentucky. Van Dorn's first order of business was to drive Curtis out of Arkansas. On March 4, Van Dorn started north from Fayetteville, Arkansas, with approximately 16,000 troops. His plan was to advance north as quickly as possible and to surprise Curtis's scattered army before it had time to concentrate. After three days of forced marching through harsh winter weather, the Confederates approached Curtis's position. The Rebel soldiers were cold, hungry and exhausted, but Van Dorn was determined to press the attack.
Learning of Van Dorn's advance, Curtis concentrated the 10,500 soldiers under his command and established a strong defensive position on Pea Ridge. The two armies engaged from March 6-8, 1862, with the Army of the Southwest emerging victorious. The resounding Union victory secured Federal control of Missouri and it enabled the Union to focus on other areas in the Mississippi Valley. Much of the army was transferred to Milliken's Bend, Louisiana, March 13-26, and organized as the 14th Division of the 13th Army Corps (General Orders, No. 50, 13th Army Corps).
After the Battle of Pea Ridge, Curtis severed ties with his supply lines and pursued Van Dorn's army farther into Arkansas, while living off of the land, much as Major General William T. Sherman would do in Georgia two years later. Curtis never caught up with Van Dorn, but he did force the Confederate state government to temporarily abandon Little Rock when his troops threatened the state capital in May 1862.
In July 1862, Curtis and the Army of the Southwest moved across northern Arkansas toward the Mississippi River port of Helena. On July 12, 1862, three regiments of Texas cavalry commanded by Colonel William H. Parsons tried to prevent three brigades of the Army of the Southwest from crossing the Cache River. Although outnumbered, the Federals, commanded by Colonel Charles E. Hovey, repulsed poorly organized Confederate attacks until reinforcements arrived. The Union victory at the Battle of Cotton Plant (aka the Battle of Hill's Plantation) opened the door for the occupation of Helena on July 12, 1862.
For the next few months, the Army of the Southwest underwent a flurry of abbreviated command changes as the War Department siphoned off its troops in support of the Vicksburg Campaign. On August 29, 1862, after Curtis took leave to travel to a railroad convention in Chicago, Brigadier General Frederick Steele assumed command of the army (General Orders, No. 42, Army of the Southwest). Steele served only briefly before being replaced by Eugene A. Carr on October 7, 1862, (General Orders, No. 50, Army of the Southwest). By this time much of the Army of the Southwest had been transferred to the Army of the Tennessee and the Army of the Mississippi. On November 14, 1862, the War Department ordered Brigadier General Willis A. Gorman "to report in person to Major General S. R. Curtis, commanding Department of the Missouri, at Saint Louis, Mo., for orders." Curtis placed Gorman in charge of the Army of the Southwest and the troops in the District of Eastern Arkansas. On December 13, 1862, the two bodies were merged, ending the existence of the Army of the Southwest.