The Battle of First Manassas (alternately known as First Bull Run) was fought on July 21, 1861 near the railroad junction of Manassas in Virginia. Union commander Irvin McDowell's 35,000 green troops were pitted against the 30,000 man combined army (J. Johnston's Army of the Shenandoah had been shipped by rail) under Confederate generals P.G.T. Beauregard and J. Johnston. Even though Johnston was the ranking Confederate officer on the field, he relinquished command to Beauregard.
On the morning of July 21, both commanders had developed battle plans. Both McDowell and Beauregard had identical plans: to push forward across Bull Run with their respective right flanks to attack the enemy left. In addition, McDowell ordered Davies and Tyler's divions to make diversionary attacks at Blackburn's Ford and Stone Bridge, respectively. McDowell's attack got under way faster, and the Confederate left flank, guarding the Stone Bridge, (3 brigades, commanded by "Shank" Evans, Bee, and Bartow) came under attack by the Union divisions under Hunter and Heintzleman.
Evans delayed the Union advance by placing his brigade on Matthew hill, but then Tyler's division forced a crossing of the Stone Bridge. The Confederate line was subsequently pushed back as far as the Henry House hill, a plateau about a mile from Evan's initial position.
Beauregard, alarmed at the sounds of fighting near his left flank, called off his own attack and shifted all extra units to his left. In the course of the fighting, Colonel Bee rallied his men with the cry, "There stands Jackson like a stone wall." From then on, Jackson was to be fondly referred to as Stonewall.This, and J.E.B. Stuart's cavalry countercharge that captured some Union cannon, helped turn the tide of battle.
Beauregard then noticed that his left flank had swelled so that his flank overlapped the Union right flank. He seized the opportunity and ordered a general attack. The green and inexperienced Union army panicked. They, along with the crowds of picnickers that had tagged along to "watch the fun" dispersed, and retreated (or routed) all the way to Washington D.C. The Confederate army was too disorganized to pursue, and simply feasted on captured picnic lunches and rested.
This was the first major battle of the Civil War, and resulted in a Confederate victory. The Union counted about 3,000 casualties, and the Confederacy about 2,000.