Civil War Union Major General. He graduated from the United States Military Academy in West Point, New York, in 1843, placing 16th out of 39 (his classmates included future Union Generals William B. Franklin, Ulysses S. Grant, and Joseph J. Reynolds, as well as future Confederate Generals Roswell Ripley, Samuel G. French, and Franklin Gardner). His service after graduation was typical, serving in the Mexican War and on the Western American frontier against the Plains Indians. When the Civil War started, he had the rank of Captain, 4th United States Infantry in the Regular Army, and served as commandant of cadets at West Point. In May 1861, he was promoted to Major of the newly-raised 13th United States Infantry, but his time with the new regiment was brief. In November 1861, he was promoted to Brigadier General, U.S. Volunteers, and commanded a brigade along the Rappahannock River during the Spring 1862 Peninsular Campaign. In the August 1862 Battle of Cedar Mountain, where the Union forces were soundly defeated by Confederate General Stonewall Jackson, he sustained a severe wound while in command of the II Corps' 2nd Division, but was highly commended for his performance and bravery, which led to his promotion to Major General, U.S. Volunteers (and a brevet of Colonel, U.S. Regular Army). During his convalesces from his Cedar Mountain wound, he served on a commission that investigated Colonel Dixon Miles' September 1862 surrender of Harper's Ferry, Virginia. He then served with Major General Nathaniel Banks in operations in Louisiana and Mississippi, leading the left wing of the Union Army that forced the capitulation of Port Hudson, Mississippi, in July 1863. He subsequently commanded simultaneously the XXII Corps and the Department of Washington to the end of the war. As Commander of the Capital District, he was present when President Abraham Lincoln succumbed to an assassin's bullet, and was detailed to escort the President's body from the Petersen House, where he died, to the White House. When he was mustered out of Volunteer service in September 1866, he received the brevet of Brigadier and Major General, U.S. Regular Army and was promoted to Colonel and Commander of the 12th United States Regular Infantry. In 1869, he was advanced to Brigadier General in the Regular service, and retired with that rank in 1885.