Confederate General Robert E. Lee defeats Union General John Pope at the Second Battle of Bull Run. Union General George McClellan's Peninsular campaign had stalled miserably earlier in the summer. President Lincoln and General-in-Chief Henry Halleck were so frustrated with McClellan’s efforts they opted to re-assign a large part of McClellan's Army of the Potomac and send it to General John Pope's newly formed Army of Virginia.
General Lee guessed that McClellan had no plans to attack Richmond, so he sent General Thomas J. "Stonewall" Jackson north to keep an eye on Pope's force. When it became apparent the Yankees were abandoning the peninsula, Lee moved more of his force northward to defeat Pope before reinforcements arrived.
After Jackson raided a major Union supply depot at Manassas, Pope began to pursue Jackson. But he could not find the Rebel force, which was hidden in the woods around Bull Run. Pope issued contradictory orders that frustrated his troops, who marched back and forth for two days but was unable to find Jacksons troops.
By August 28, Jackson was made aware that General James Longstreet's corps was nearby. Jackson's men emerged from the woods and attacked a Union division late in the day, but the fighting ended in a standstill. On August 29, Pope attacked the rebels, the Confederates mauled the Union troops, and by August 30 Pope was forced to retreat. His army lost over 16,000 men to the Confederates' 9,000.
Thus, the second defeat to the Yankees on the same ground as the first great infantry battle of the war more than year ealier.
Known in the North as "The Second Battle of Bull Run"
and in the South as "Second Manassas"