What year did James Garfield fight in the Civil War?

The future US president commanded troops of the 42nd Ohio Volunteer Regiment beginning in late 1861, under General Don Carlos Buell. In 1862 he fell ill, but returned to serve for nearly a year as chief of staff to General William Rosecrans, famously avoiding more Union losses at the Battle of Chickamauga (Sept. 19-20, 1863). After a promotion to Major General, Garfield left the Army to resume the House seat to which he had been elected in 1862.