Later that evening, Hays (although still a brigadier general and junior in rank to Caldwell), was assigned to command the II Corps. He led the corps throughout the summer until permanent command was given to Maj. Gen. Gouverneur K. Warren in mid-September. In November, Hays was appointed provost marshal of the southern district of New York, and was also promoted to major in the regular army. At the expiration of his term in February 1865, Hays rejoined the Army of the Potomac at Petersburg and served again in the II Corps, this time commanding the 2nd Division. He was appointed a brevet brigadier general in the regular army on March 13, 1865, for gallant conduct, but on April 6 he was relieved of command for sleeping on duty and thus failing to prepare his troops for departure as they pursued Confederate forces. His brevets were revoked and Brig. Gen. Francis C. Barlow was assigned to lead the division. From that date, Hays commanded the Artillery Reserve of the Army of the Potomac until he was mustered out of volunteer service in January 1866. Reverting to his permanent rank of major of the 5th U.S. Artillery, Hays served on various posts, commanding Fort Independence in Boston Harbor from April 1873 until his death there almost two years later. He was buried in Yonkers, New York, but was re-interred at West Point Cemetery in 1894. Attribution: