Bent served in the Missouri State Guard with the Confederate Army, fighting at the Battle of Wilson's Creek near Springfield, Missouri, on August 10, 1861; and at the First Battle of Lexington near Lexington, Missouri, on September 20, 1861; both were Confederate victories. As a member of the 1st Missouri Cavalry Regiment, he fought at the Battle of Pea Ridge in Arkansas, March 6–8, 1862, which was a Union victory. When the Missouri cavalry was converted to infantry, Bent became attached to Landis' Battery, Missouri Light Artillery, the horse artillery of General Mathew F. Greene's Missouri Brigade; this was part of General Sterling Price's division. His artillery unit participated in the siege and retreat from Corinth, Mississippi, where it stayed behind to cover the retreat of 66,000 Confederates under the command of P.G.T. Beauregard.