Engineering duty on the Atlantic Coast With the outbreak of the Civil War in early 1861, Gillmore was assigned to the staff of Brigadier General
Thomas W. Sherman and accompanied him to
Port Royal, South Carolina. After being appointed as a
brigadier general, Gillmore took charge of the siege operations against
Fort Pulaski. A staunch advocate of the relatively new naval rifled guns, he was the first officer to effectively use them to knock out an enemy stone fortification. More than 5,000 artillery shells fell on Pulaski from a range of 1,700 yards during the short siege, which resulted in the fort's surrender after its walls were breached. Although he was one of the best artillerists and engineers in the army he was not well respected by his men.
Service in Kentucky After an assignment in New York City, Gillmore traveled to
Lexington, Kentucky, where he supervised the construction of Fort Clay on a hilltop commanding the city. Gillmore commanded a division in the
Army of Kentucky then the District of Central Kentucky. Though long associated with engineering and artillery, Gillmore's first independent command came at the head of a cavalry expedition against Confederate General
John Pegram. Gillmore defeated the Confederates at the
battle of Somerset for which he was given a
brevet (military) promotion to colonel in the U.S. Army.
Return to the Department of the South Gillmore was assigned to replace Major General
David Hunter in charge of the
X Corps. In addition, Gillmore commanded the
Department of the South, consisting of North and South Carolina, Georgia and Florida, with headquarters at
Hilton Head, from June 12, 1863, to May 1, 1864. Under his direction, the army constructed two earthen forts in coastal South Carolina—Fort Mitchel and Fort Holbrook, located in the Spanish Wells area near Hilton Head Island. He then turned his attention against
Charleston, South Carolina. Initially successful in an attack on the southern end of Morris Island on July 10, Gillmore had enough confidence to assault
Fort Wagner on the north end of the island. The following day he launched the
first attack on Fort Wagner which was defeated. He assembled a larger assault force and with the assistance of
John A. Dahlgren's naval fleet planned a second attack. On July 18, 1863, Gillmore's troops were repulsed with heavy losses in the
Second Battle of Fort Wagner. Gillmore's divisional commander, General
Truman Seymour was wounded and two brigade commanders,
George Crockett Strong and
Haldimand S. Putnam were killed in the attack.
The Gillmore Medal First issued on October 28, 1863, the Gillmore Medal (also called the Fort Sumter Medal) was struck and issued by Gilmore to all Union soldiers who had served under his command in the fighting around Charleston during 1863.
Gillmore Orders His Command Integrated Among the troops who assaulted Ft. Wagner was the
54th Massachusetts, a regiment of African-Americans led (as required by regulation) by white commissioned officers. Gillmore had ordered that his forces be integrated and that African-Americans were not to be assigned menial tasks only, such as KP or latrine duty, but instead they were to carry arms into battle. They and their assault on Ft. Wagner were the subject of the 1989 Civil War movie
Glory.
The Swamp Angel Gillmore decided on siege operations
to capture Fort Wagner using innovative technology such as the 25-barreled
Requa gun and calcium flood light to blind opponents during trenching efforts. He also implanted a massive
Parrott rifle, nicknamed the "Swamp Angel", which fired 200-pound shots into the city of Charleston itself. Despite the swampy ground Union troops were able to work their way toward Fort Wagner. Meanwhile, Gillmore's artillery pounded Fort Sumter into rubble. On September 7, 1863, Gillmore's forces captured Fort Wagner. In February 1864, Gillmore sent troops to Florida under the command of General Truman Seymour. Despite orders from Gillmore not to advance into the interior of the state, General Seymour advanced toward Tallahassee, the capitol, and fought the largest battle in
Florida, the
Battle of Olustee, which resulted in a Union defeat.
Virginia and Washington DC In early May, Gillmore and the X Corps were transferred to the
Army of the James and shipped to
Virginia. They took part in the
Bermuda Hundred operations and played a principal role in the disastrous
Drewry's Bluff action. Gillmore openly feuded with his superior,
Benjamin F. Butler over the blame for the defeat. Gillmore asked for reassignment and left for
Washington, D.C. In July 1864, Gillmore helped organized new recruits and invalids into a 20,000-man force to help protect the city from a threat by 10,000
Confederates under
Jubal A. Early, who had reached the outer defenses of the Union capital. Federal reinforcements from the Gulf coast were being transferred East at the time and Gillmore was put in command of a detachment of the
XIX Corps which had been quickly diverted to the defense of the capital at the
battle of Fort Stevens.
Close of the War With the threat to Washington over the XIX Corps was transferred to the
Army of the Shenandoah and Gillmore was reassigned to the Western Theater as inspector of military fortifications. As the war was drawing to an end he was reassigned to command of the Department of the South one final time and was in command when Charleston and Fort Sumter were finally turned over to Union forces. He received brevet promotions to Brigadier General and Major General in the U.S. Army for the campaign against Battery Wagner, Morris Island and Fort Sumter dated March 13, 1865. With the war over, he resigned from the volunteer army on December 5, 1865, and returned to being a major in the Corps of Engineers. ==Postbellum career==