Created on October 28, 1861, under the command of General Albert S. Johnston, the Central Army of Kentucky was the main military force in the Confederacy's Western District until March 29, 1862, when it merged with the Army of the Mississippi (aka Army of Mississippi).
The Central Army of Kentucky traces its roots to a provisional Confederate army assembled soon after the beginning of the Civil War. On June 25, 1861, Samuel Cooper, Adjutant General of the Confederate States of America, informed Brigadier General Leonidas Polk that the Confederate War Department had promoted Polk to the rank of major general of the provisional army and placed him in command of a large area in the west, including parts of Alabama, Mississippi, Louisiana, Arkansas, and Tennessee. Two weeks later, on July 4, Assistant Adjutant General Jonathan Withers issued Special Orders, No. 88 announcing that Polk's area of command will "hereafter constitute Department No.2." On September 10, 1861, Withers issued Special Orders, No. 149 announcing that General Albert Sidney Johnston was assigned to command Department No. 2 (aka the Western Department). Johnston assumed command and assigned his staff officers on the next day.
Upon assuming his command of the Western Department, Johnston went to work organizing the Confederate forces in the West. His most pressing challenge was trying to defend a three-hundred-mile front stretching from the Cumberland Gap in the Appalachians all of the way to the Mississippi River. On October 28, 1861, Johnston issued Special Orders, No. 51 (Western Department) assuming "immediate command of the army corps of Central Kentucky." The order went on to name Major General William J. Hardee as commander of the army's first division (4,000 soldiers) and Brigadier General Simon B. Buckner as commander of the army's second division (6,000 soldiers).
Outnumbered by Northern foes roughly two-to-one, Johnston decided to consolidate his forces at Bowling Green, Kentucky, the heart of his defensive line. On December 4, 1861, Johnston issued General Orders, No. 127 announcing that the "command of the Central Army of Kentucky is devolved upon Major-General Hardee." Johnston, however, retained command of the Western Department.
Following the loss of Fort Henry on February 6, 1862, Johnston acted to save Fort Donelson on the Cumberland River near the Kentucky-Tennessee border. He ordered Buckner and Brigadier General John B. Floyd to march a detachment of 8,000 soldiers from the Central Army of Kentucky to reinforce the garrison at Fort Donelson. Despite the reinforcements, the fort fell to Ulysses S. Grant's forces on February 16.
After the fall of Fort Donelson, Johnston's headquarters at Bowling Green became untenable. Johnston chose to evacuate Bowling Green, Kentucky, on February 13, 1862, and to fall back to Murfreesboro, near Nashville, Tennessee. While there he issued Special Orders, No. 4 on February 23, 1862, reorganizing the Central Army of Kentucky under his personal command. The newly-configured army consisted of three divisions commanded by Hardee, Major General George B. Crittenden, and Brigadier General Gideon Pillow, in addition to a reserve brigade led by Brigadier General John C. Breckinridge. At that time, the Central Army of Kentucky numbered roughly 17,000 soldiers.
Pressed by Major General Don Carlos Buell's Army of the Ohio, Johnston evacuated central Tennessee and headed for a rendezvous with General P.G.T. Beauregard's Army of the Mississippi at Corinth, Mississippi, in March. On March 29, 1862, Johnston issued General Orders, Nos. 1-8 announcing the consolidation of the Central Army of Kentucky with Beauregard's army. The combined force, under Johnston's command, assumed the name of Army of the Mississippi, thus ending the existence of the Central Army of Kentucky. The Army of the Mississippi (aka the Army of Mississippi) later morphed into the Army of Tennessee, the Confederacy's main force in the Western Theater of the Civil War.