It was created to defend the Shenandoah Valley of Virginia from Union Army attacks during the early months of the war.

On May 15, Joseph E. Johnston replaced Jackson as commander of Harpers Ferry and continued to receive additional regiments from throughout the Confederacy.

[1] In mid-June, forces from the Union Department of Pennsylvania, commanded by Robert Patterson, began moving south towards Harpers Ferry.

[2] After spending almost two weeks waiting on the Potomac and receiving reinforcements, Patterson started advancing towards Winchester but had moved only 5 miles (8.0 km) before encountering Stuart's regiment screening Johnston's army.

[4] On the morning of July 21, McDowell launched his own attack on the Confederate left wing, defended by one of Beauregard's brigades.