When the issue of secession reached a crisis, Cleburne sided with the Southern states. His choice was not due to any love of slavery, which he claimed not to care about, but out of affection for the Southern people who had adopted him as one of their own. As the crisis mounted, Cleburne joined the local militia company (the Yell Rifles) as a private soldier. He was soon elected captain. He led the company in the seizure of the U.S. Arsenal in Little Rock in January 1861. When Arkansas left the Union, the Yell Rifles became part of the 1st Arkansas Infantry. Cleburne's regiment was assigned to the force under William Hardee, training in northeast Arkansas and conducting brief operations in southeast Missouri before Hardee's force was ordered to cross the Mississippi River and join Albert Sidney Johnston's Army of Central Kentucky in the fall 1861. The 1st Arkansas was designated the 15th Arkansas in late 1861. Cleburne was promoted to brigadier general on March 4, 1862.