On July 16, 1861, the Union Army under General Irvin McDowell began marching from Washington, D.C., toward Bull Run to dislodge or destroy General P.G.T. Beauregard's forces stationed there. Initial contact came on July 17, and Beauregard called on General Joseph Johnston for reinforcements from the Shenandoah Valley. The next day, the lead elements of the Union army clashed with Confederate forces at Blackburn's Ford, a small action that convinced McDowell to try a flank march around the western end of the Confederate line at Stone Bridge rather than attack the strong forts around the rail junction directly. At Mayfield, men could hear the fighting at Blackburn's Ford four miles to the north. McDowell hoped his flanking movement would force the Confederates to abandon their earthworks and the rail junction. On July 21, as fighting broke out seven miles west on Matthews and Henry House Hills, Colonel George Terrett's brigade and some local militia remained in the forts around Manassas Junction while most Confederate forces posted along Bull Run moved west to meet the Union attack. Later that afternoon, as Beauregard's reinforcements arrived from the Shenandoah Valley, Colonel A.P. Hill's 13th Virginia Infantry regiment was sent to help defend the railroad junction. After a long day of fighting, McDowell was defeated and retreated to Arlington, leaving the Confederate Army in full control of the area.
