At the beginning of the war, Parke was promoted to captain of topographical engineers in September 1861. In November, he was appointed to brigadier general. In the beginning of 1862, Parke accompanied General Ambrose E. Burnside's expedition to North Carolina, before he received a promotion to the rank of lieutenant colonel after the capture of Fort Macon. Parke was promoted major general of volunteers in July 1862 and was assigned as chief of staff of the 9th corps during the Maryland campaign, being engaged at South Mountain and Antietam, and in the pursuit of the enemy to Warrenton. Just before the battle of Fredericksburg, Parke was reinstated as the chief of staff of the Army of the Potomac. He participated in the movement of the 9th corps into Kentucky before he was put in command during the march to Vicksburg. In the reoccupation of Jackson, Mississippi, Parke was in command of the left wing of Gen. Sherman's army. In the East Tennessee campaign, he was engaged at Blue Spring in the defense of Knoxville. Parke was engaged at the battle of the Wilderness and the battle of Spotsylvania Court House before he led a division into the Richmond campaign of the Army of the Potomac. During the advance toward Richmond, Parke was disabled by illness until August 1864 when he resumed command of the 9th corps before Petersburg, and stayed with the army until the surrender at Appomattox Court House.
