The opening fight at Brawner Farm revealed Stonewall Jackson's position north of Groveton. In response, General John Pope ordered his entire force - nearly 65,000 Federal troops - to converge on the Confederates and bring them to battle. This directive lead the army back to the First Manassas battlefield, stirring poignant memories of the previous year's defeat.
Pope remained confident of victory at the daybreak on August 29. The Federal commander assumed Jackson's outnumbered force was isolated and in retreat. Pope believed his troops were positioned to prevent Jackson's escape. He fully expected that Jackson would be destroyed before Confederate reinforcements could intervene. Tactical realities were a bit different. Instead of "retreating," Jackson's troops had taken a strong defensive position along the embankments of an unfinished railroad. By noon, General James Longstreet had nearly 30,000 men - the rest of Lee's Confederate army - deploying on the battlefield. Pope, however, discounted all evidence that did not fit his vision of total victory.
Source: U.S. Department of the Interior, National Park Service