After November 18, 1862, General Seymour was sent to the Department of the South where he served as chief of staff to the commanding general from January 8 to April 23, 1863. He led a division on Folly Island, South Carolina, on July 4, participated in the attack on Morris Island on July 10, and commanded the unsuccessful attack on Fort Wagner on July 18. Seymour gained notoriety for this controversial attack. He had placed the famous 54th Massachusetts Volunteer Infantry, the black regiment about which the 1989 film "Glory" was made, in the vanguard of what most thought would be a feckless attack. He was also seriously wounded by grapeshot there and saw little field duty for the rest of 1863.