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. The Georgians won out and drove the 13th Massachusetts back down the steep slopes. With the gap firmly in Confederate control, Col. Evander M. Law's brigade was ordered up and over the ridge to the north of the gap to attack the Federal right. At the same time, Brig. Gen. Cadmus M. Wilcox was sent with three brigades to the north, through Hopewell Gap, to outflank the Federal position and attack its rear. When Law's brigade came down the eastern slope of the mountain and attacked the Federal right, Ricketts sent the 84th New York against them, temporarily checking Law's advance. The 2nd and 20th Georgia, however, pressed down the slopes to the south and soon attacked the Federal left. 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. Aftermath In terms of casualties, the battle was small, with only 100 casualties on both sides combined, but had major strategic consequences. Ricketts failed to fully comprehend the importance of keeping the two wings of the Confederate army apart. Rather than entrenching his force in a strong defensive position at the gap, the easiest and quickest crossing of the Bull Run Range, he left only cavalry there while he sat a half-day's march away at Gainesville, protecting the railroad, a job much more suited for his cavalry. As such, he lost the advantage and the only hope his small force had in seriously hindering Longstreet's advance. 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. Battlefield preservation The Thoroughfare Gap Battlefield was listed on the National Register of Historic Places in 1999. The Civil War Trust (a division of the American Battlefield Trust) and its partners have acquired and preserved of the battlefield. The battlefield is accessible from a walking trail adjacent to the