Thoroughfare Gap

On August 28, 1862, fighting broke out in Fauquier County and Prince William County, Virginia, in an engagement known as Thoroughfare Gap, or alternatively as Chapman's Mill. This clash formed part of the Northern Virginia Campaign during the American Civil War. Maj. Gen. James Longstreet led Confederate troops that pushed back the opposing Union force, commanded by Brig. Gen. James B. Ricketts along with Col. Percy Wyndham. The victory cleared the way for Longstreet's corps to join forces with that of Thomas J. "Stonewall" Jackson, setting the stage for the Second Battle of Bull Run, also called Second Manassas.

Background

Stonewall Jackson's corps, part of the Army of Northern Virginia, passed through Thoroughfare Gap on August 26 while moving to strike the Union supply depot at Manassas Junction. Union forces reacted a day later when Maj. Gen. Irwin McDowell left Warrenton bound for Manassas Junction, hoping to catch Jackson there. Concerned about the vulnerability of his left flank, McDowell sent Brig. Gen. James B. Ricketts's brigade toward the Gap along with the 1st New Jersey Cavalry, commanded by Sir Percy Wyndham. Wyndham took up a position holding the Gap itself, while Ricketts halted six miles further east at Gainesville. At the same time, Maj. Gen. James Longstreet's corps was tracing the route Jackson had already taken, drawing near the Gap from the western side as the night of August 27 set in.

Battle

At half past nine in the morning on August 28, cavalrymen under Wyndham ran into the leading elements of Longstreet's column just as they were working to block the road east of the gap by chopping down trees. Wyndham quickly sent a rider back to Ricketts, who was posted at Gainesville, warning him of the danger. Ricketts, however, moved forward at a sluggish pace, and by two in the afternoon his men had covered only the three miles to Haymarket. By this time Wyndham's cavalry had already been pushed out of the gap, which now belonged to Longstreet. Even so, the Union position remained far from hopeless, since a chain of low ridges to the east offered strong ground from which to defend the approach to Gainesville, and the Confederates had yet to seize the high points north and south of the pass.

Facing this threat, Longstreet devised a plan to hold the gap from the elevated ground on both flanks and then swing around the Union line stationed on the eastern ridge. He directed the 9th Georgia, part of Col. George T. Anderson's brigade, toward Chapman's Mill east of the gap to beat back an advance by the 11th Pennsylvania. In a twist of fate, the Pennsylvania troops first had to clear away the very trees Wyndham's men had felled that morning before they could even reach the position. This delay bought Anderson enough time to send half his brigade up the northern slope to claim the high ground, all while keeping enough troops behind to hold off the 11th Pennsylvania. South of the gap, meanwhile, the 2nd and 20th Georgia regiments, belonging to Henry Benning's brigade, dashed up the western face of the ridge in a footrace against the 13th Massachusetts, which was climbing from the east. The Georgia men reached the top first and shoved the Massachusetts troops back down the steep hillside.

With Confederate control of the gap now secure, Longstreet ordered Col. Evander M. Law's brigade over the northern ridge to strike the Union right flank. Simultaneously, Brig. Gen. Cadmus M. Wilcox led three brigades on a six mile march north through Hopewell Gap, aiming to swing behind the Federal line and hit it from the rear. As Law's men descended the eastern side of the mountain and fell upon the Union right, Ricketts countered by throwing the 84th New York into their path, halting Law's momentum for a time. But the 2nd and 20th Georgia continued pushing down from the south and soon struck the Union left as well. Seeing his line grow more precarious by the minute, Ricketts chose to withdraw toward Gainesville, abandoning the gap to the Confederates before Wilcox's flanking march could seal off his escape route.

Aftermath

The engagement itself cost few lives, only 100 casualties combined, yet its impact on the campaign proved far greater than its size suggested. Ricketts did not grasp how critical it was to keep the Confederate army's two wings separated. Instead of digging in at the gap, the fastest and easiest route through the Bull Run Range, he stationed only cavalry there and kept his main force a half-day's march away at Gainesville, guarding the railroad, a task better suited to mounted troops than infantry. This decision cost him the edge he needed, along with the one real chance his small command had to slow Longstreet's march in a meaningful way. Because he failed to act, the two Confederate wings were free to join forces at Manassas, a development that all but guaranteed Pope would be defeated at the Second Battle of Bull Run on August 29.