 A graduate of the United States Military Academy in 1850, Grover was stationed in the western frontier before being transferred to help in defense preparations of Washington, D.C., at the outbreak of the Civil War.He was appointed brigadier general of volunteers in April 1862, but with a date of rank of April 14, 1861, the day after the evacuation of Fort Sumter, making him one of the more senior generals in the Army.He served as a brigade commander in the III Corps of the Army of the Potomac, in which role he won distinction at the Battle of Williamsburg and was brevetted lieutenant colonel in the regular army, and winning promotion to full colonel for gallantry at the Battle of Seven Pines.