the Army of the Potomac's V Corps during the Peninsula Campaign of April–July 1862. He commanded the left wing of the Reserves at Mechanicsville on June 26, Gaines' Mill on June 27, Glendale on June 30 and led the division at Malvern Hill on July 1 after McCall was captured at the Battle of Glendale. After the Peninsula Campaign, the Pennsylvania Reserves joined the III Corps of the Army of Virginia, later I Corps in the Army of the Potomac. Seymour performed well at the battles of Second Bull Run, South Mountain, and Antietam in the latter half of 1862, especially in his brigade's capture of Frosttown Gap, Maryland, on September 14. Seymour took command of the Reserves after Brig. Gen. George G. Meade became acting corps commander. He received the brevet from the regular army of lieutenant colonel after South Mountain and that of colonel after Antietam. 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. The Battle of Olustee Maj. Gen. Quincy A. Gillmore, commanding general of the Department of the South, placed Seymour in charge of the newly created District of Florida. The division made an expedition to Florida in February 1864, landing at and taking possession of Jacksonville. Subsequently, Gillmore returned to South Carolina and left Seymour in tactical command. On February 20, Seymour's force of about 5,500 men met a Confederate force of about 5,000, commanded by Brigadier General Joseph Finegan. The battle took place near the town of Olustee, about 40 miles west of Jacksonville. The ensuing battle produced some of the heaviest losses, by percentage, of any major battle of the war. Although Seymour's division inflicted nearly 1,000 casualties, it received nearly 2,000 in return. General Seymour's force returned, defeated,