Pope however, saw this as an opportunity destroy Jackson's force. Convinced he had Jackson trapped, Pope moved the bulk of his force to attack him. He moved against Jackson on both flanks, hoping to overwhelm the smaller army. Jackson was able to repulse the initial assault however, and the Confederate line held strong. The fighting was fierce, and resulted in high numbers of casualties on both sides.
It was at this point that Longstreet's reinforcements arrived, and took up positions along Jackson's right flank. Unaware of Longstreet's arrival, Pope renewed his attacks against the Confederate position. Confederate mass artillery however, devastated the advancing V Corps. Longstreet then launched a counter attack of 28,000 men, completely smashing the Union Left flank. This assault was the largest simultaneous mass assault in the war. The result was an immediate Union retreat back to Bull Run. The Union was defeated, and only avoided a rout due to the actions of the rear guard.
The events of August 28–30, 1862 paved the way for the first invasion of the north by the Confederate army.