On April 16, 1862 President Abraham Lincoln appointed Buford Brigadier General of U.S. Volunteers, to rank from April 15, 1862. Buford commanded the 1st Brigade, 3rd Division, Army of the Mississippi during the siege and Battle of Corinth. In the final days of 1862, he served on the court-martial that convicted Major General Fitz John Porter of cowardice and disobedience. On November 29, 1862 he was appointed Major General of U.S. Volunteers but this appointment expired on March 4, 1863 and he reverted to brigadier general on that date. For the rest of the war, Buford served as commander of the District of East Arkansas. Buford was mustered out of the army on August 24, 1865. On July 5, 1867, President Andrew Johnson nominated Buford for appointment to the brevet grade of major general of volunteers, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on July 19, 1867.