At the outbreak of the Civil War, Sykes was assigned as a
major in the new
14th U.S. Infantry. At the
First Battle of Bull Run, he commanded the Regular Infantry
Battalion, a collection of eight
regular army companies from different regiments, the only regulars on the field. Sykes received command of a brigade of regulars after Bull Run, and was promoted to brigadier general of volunteers on September 28. He led his regulars in the Peninsula Campaign and rose to division command in May 1862 in the new V Corps. His men, who often referred to themselves as "Sykes' Regulars", distinguished themselves defending their position at
Gaines' Mill during the
Seven Days Battles, before the Union line broke elsewhere. Sykes was the only division commander in the Army of the Potomac not rewarded with a promotion to major general after the Seven Days Battles. He continued to lead his division at
Second Bull Run,
Antietam, and
Fredericksburg, although it was not heavily engaged in the latter two battles. At
Chancellorsville, his regulars led the advance into the Confederate rear at the start of the battle. Sykes' division engaged Maj. Gen.
Lafayette McLaws' division on the Orange Turnpike. Sykes' division was forced to retreat after being attacked on the right flank by Maj. Gen.
Robert E. Rodes' division, then the army commander, Maj. Gen.
Joseph Hooker, nervously recalled his advance to a defensive position; and Sykes' men were not engaged for the remainder of the campaign. Sykes finally received a promotion to major general of volunteers on November 29, 1862. When corps commander Maj. Gen.
George G. Meade was promoted to lead the
Army of the Potomac on June 28, 1863, Sykes assumed command of the V Corps. :
Gouverneur K. Warren,
William H. French,
George G. Meade,
Henry J. Hunt,
Andrew A. Humphreys and George Sykes in September 1863 At the
Battle of Gettysburg, Sykes' corps fought in support of the beleaguered
III Corps on the Union left flank. In his 1st Division (
Brig. Gen. James Barnes), the fabled defense of
Little Round Top was led by brigade commander Col.
Strong Vincent and the
20th Maine Infantry under Col.
Joshua Lawrence Chamberlain. His 3rd Division, the
Pennsylvania Reserves, led by Brig. Gen.
Samuel W. Crawford, attacked from Little Round Top, drove the
Confederates across the "Valley of Death" and ended the deadly fighting in the
Wheatfield. On October 16, 1863, Sykes was promoted to lieutenant colonel in the regular army. Sykes and his V Corps served in the
Bristoe Campaign and in the
Mine Run Campaign in the fall and winter of 1863. In March 1864, upon recommendation from the V Corps medical director due to severe
sciatica, Sykes was relieved of command of the V Corps and sent to uneventful duty in the Department of
Kansas. During
Price's Raid in 1864, he was replaced with
James G. Blunt. ==Postbellum career==