In 1861 Ricketts was serving as a captain in the regular army. In July he commanded a battery at the First Battle of Manassas, where he was shot four times and taken prisoner. Exchanged in January 1862 he was promoted to Brigadier General of Volunteers and assigned to command of a Division of McDowell's corps. At Sharpsburg, he had two horses killed from under him and he was badly injured when the second one fell on him. He did not return to the field until March 1864Ø¢eing assigned to a Division of Sedgwick's VI Corps, which he led through Grant's Overland Campaign. In July 1864, his command, numbering 3,350 muskets, was hurried north to oppose Early's raid on Washington, D.C. At Cedar Creek in October, while temporarily commanding the corps, he was wounded by a bullet through his chest which disabled him for life. Nonetheless, he returned to command of his Division two days before Appomattox. On January 3, 1867, he retired from active service as a Major General for disability from wounds received in battle; however, he continued to do court-martial duty until 1869. He lived in Washington, D.C. until his death, September 22, 1887.