small stream, NE Va., c.30 mi (50 km) SW of Washington, D.C. Two important battles of the Civil War were fought there: the first on July 21, 1861, and the second Aug. 29–30, 1862. Both battlefields are included in Manassas National Battlefield Park (est. 1940).
The first battle of Bull Run (or first battle of Manassas) was the first major engagement of the Civil War. On July 16, 1861, the Union army under Gen. Irvin McDowell began to move on the Confederate force under Gen. P. G. T. Beauregard at Manassas Junction, Va. Gen. Robert Patterson's force at nearby Martinsburg was to prevent the Confederate army under Gen. Joseph E. Johnston at Winchester from uniting with Beauregard but failed, and by July 20 part of Johnston's army had reached Manassas. On July 21, McDowell, turning Beauregard's left, attacked the Confederates near the stone bridge over Bull Run and drove them back to the Henry House Hill. There Confederate resistance, with Gen. Thomas J. Jackson standing like a “stone wall,” checked the Union advance, and the arrival of Gen. E. Kirby Smith's brigade turned the tide against the Union forces. The unseasoned Union volunteers retreated, fleeing along roads jammed by panicked civilians who had turned out in their Sunday finery to watch the battle. The retreat became a rout as the soldiers made for the defenses of Washington, but the equally inexperienced Confederates were in no condition to make an effective pursuit. The South rejoiced at the result, while the North was spurred to greater efforts to win the war.
The second battle of Bull Run (or second battle of Manassas) was also a victory for the Confederates. In July, 1862, the Union Army of Virginia under Gen. John Pope threatened the town of Gordonsville, a railroad junction between Richmond and the Shenandoah valley. Gen. Robert E. Lee sent Stonewall Jackson to protect the town, and on Aug. 9, 1862, Jackson defeated Nathaniel Banks's corps, the vanguard of Pope's army, in the battle of Cedar Mt. (or Cedar Run). When Gen. George McClellan's army was gradually withdrawn from Harrison's Landing on the James River (where it had remained after the Seven Days battles) to reinforce Pope, Lee concentrated his whole army at Gordonsville. He planned to strike before Pope could be reinforced. Pope withdrew to the north side of the Rappahannock River. Lee followed to the south side and on Aug. 25 boldly divided his army. By Aug. 28, Jackson had marched to the Union right and rear, destroyed Union communications and supplies, and stationed his troops just west of the first Bull Run battlefield, where he awaited the arrival of James Longstreet with the rest of Lee's army. Pope was attacking Jackson when Longstreet came up on Aug. 29. The attack was repulsed, but Pope, mistaking a re-formation of Jackson's lines for a retreat, renewed it the next day. After the Union troops were again driven back, Lee ordered Longstreet to counterattack. Longstreet, supported by Jackson, swept Pope from the field. The Union forces retreated across Bull Run, badly defeated. Lee's pursuit ended at Chantilly, where the Union forces stopped Jackson on Sept. 1, 1862. Pope then withdrew to Washington.