On August 26, Maj. Gen. Stonewall Jackson led his corps of the Army of Northern Virginia through Thoroughfare Gap, on his way to raiding the Union supply depot at the Manassas Junction.

[3] At 9:30 a.m. on August 28, Wyndham's troopers encountered Longstreet's vanguard while attempting to fell trees across the road on the east side of the gap.

Ricketts's advance was slow, however, and he had only reached Haymarket, 3 miles (4.8 km) to the east, by 2 p.m. By that point, Wyndham had been driven from the Gap and Longstreet took possession of it.

The impediment allowed Anderson to send half of his brigade up to the slope to the north of the gap to occupy the high ground while still having sufficient men to repulse the 11th Pennsylvania.

To the south of the gap, the 2nd and 20th Georgia regiments from Henry Benning's brigade raced up the slopes on the west against the 13th Massachusetts, climbing up the east side.

Gen. Cadmus M. Wilcox was sent with three brigades 6 miles (9.7 km) to the north, through Hopewell Gap, to outflank the Federal position and attack its rear.

With his position rapidly becoming untenable, Ricketts decided to fall back on Gainesville, leaving the gap to the Confederates before Wilcox could cut off his line of retreat.

His failure to do so allowed the two wings of the Confederate army to unite at Manassas and virtually ensured Pope's defeat during the Second Battle of Bull Run on August 29.