The Battle of Thoroughfare Gap took place on August 28, 1862, in Fauquier County and Prince William County, Virginia. It is also known as the Battle of Chapman’s Mill. The Confederate victory created a clear path for the reunification of the Army of Northern Virginia during the Northern Virginia Campaign of the American Civil War, virtually ensuring a Confederate victory at the Second Battle of Bull Run (August 29–30, 1862).
Despite their stunning victory at the First Battle of Bull Run in July 1861, Confederate prospects were fading less than one year later. In the West, Ulysses S. Grant was having his way with Rebel defenders of vital river systems. In the East, George B. McClellan was inching his way up the Virginia Peninsula, threatening the Confederate capital at Richmond with the largest army ever assembled in North America. In addition, three Union forces in central Virginia were poised to move south through the Shenandoah Valley to support McClellan’s invasion and hopefully to bring the American Civil War to a quick conclusion.
Union Army of Virginia
By June 1862, President Abraham Lincoln lost patience with the uncoordinated federal setbacks in the Shenandoah Valley. On June 26, 1862, the President ordered the consolidation of forces commanded by major generals John C. Frémont, Nathaniel P. Banks, Irvin McDowell, and several smaller units in eastern Virginia to form the Army of Virginia. Lincoln appointed Major General John Pope to command the new army. The War Department later codified the President’s directive as General Order No. 103, dated August 12, 1862.
Pope’s immediate mission comprised three key components:
- Aid McClellan’s Peninsula Campaign by drawing troops away from Richmond, or at least preventing Confederate troops in the Shenandoah Valley from reinforcing the Rebel soldiers defending Richmond,
- Secure the Federal control of the Shenandoah Valley, and
- Protect Washington, D.C. from a Confederate assault.
Lee Forces McClellan to Retreat
By the time McClellan reached the outskirts of the Confederate capital in June 1862, Robert E. Lee had replaced Joseph E. Johnston as commander of the forces protecting Richmond. Lee boldly went on the offensive, halting the Union advance during a series of encounters collectively known as the Seven Days Battles. As Lee’s Army of Northern Virginia forced McClellan’s Army of the Potomac to withdraw down the peninsula in July, the Confederate general turned his attention to Pope’s Army of Virginia.
Lee Splits His Army
On July 13, 1862, Lee split the Army of Northern Virginia and dispatched 14,000 soldiers under the command of Major General Thomas “Stonewall” Jackson to secure Confederate railroad links with the Shenandoah Valley. Later that month, Lee sent 12,000 more men, commanded by Major General A. P. Hill, to support Jackson.
Jackson spent the next several weeks bedeviling Pope as the Union general tried to merge his forces in northern Virginia. On August 9, 1862, Jackson scored a major victory over the center of Pope’s army at the Battle of Cedar Mountain.
Later that month, on August 26, Lee daringly sent Jackson and half of the Army of Northern Virginia on a march through Thoroughfare Gap, outflanking Pope’s right wing.
Thoroughfare Gap Geography
About twenty-five miles east of Manassas, Virginia, Thoroughfare Gap is a cleft in the Bull Run Mountains between Pond Mountain and Mother Leather Coat Mountain. In 1862, a turnpike (modern-day Interstate 66) and the Manassas Gap Railroad roughly paralleled a turbid stream named Broad Run as all three traversed the opening between the mountains.
Jackson Surprises Pope
After passing through the gap unmolested, Jackson’s soldiers surprised Pope’s forces along the Orange & Alexandria Railroad, capturing a massive Union supply depot at Manassas Junction early in the morning of August 27, 1862. Overnight, Jackson pushed his soldiers north to the site of the Confederate victory at the Battle of Bull Run I the previous year.
Jackson’s success left him positioned to threaten Washington, D.C. However, it also created an opportunity for Pope to turn his entire army against Jackson’s wing while it was isolated from the rest of Lee’s army. Therefore, it became imperative for Lee to push Major General James Longstreet’s wing through Thoroughfare Gap, reunifying the Army of Northern Virginia before Pope could attack Jackson’s force.
Conflict at Thoroughfare Gap
As Pope focused on Jackson’s isolated wing, controlling the gaps through the Bull Run Mountains became almost an afterthought. Major General Irvin McDowell, commander of Pope’s 3rd Corps, dispatched Colonel Sir Percy Wyndham’s 1st New Jersey Cavalry to Thoroughfare Gap to fell trees to impede Longstreet’s progress. Brigadier General James B. Ricketts’ division soon followed but stopped at Gainesville, Virginia, about six miles east of the gap.
When Union pickets observed Longstreet’s vanguard entering the gap from the west at about 9:30 on the morning of August 28, Wyndham sent word back to Ricketts. After receiving word of Longstreet’s advance, Ricketts hurried forward reaching Haymarket, Virginia, (roughly three miles east of the gap) just after 2 pm. By then, Longstreet’s 9th Georgia Infantry Regiment had driven Wyndham’s cavalry back and taken control of the divide.
As the Georgians fanned out of the gap, they encountered Ricketts’ division approaching from the east. Greatly outnumbered, the Rebels slowly fell back to the cleft where Colonel G.T. Anderson’s brigade, arriving from the west, reinforced them. As more Confederates entered the gap, they began scaling the steep walls to secure the opening, but the Yankees had them bottled up.
With little room to maneuver, Lee ordered Brigadier General Cadmus M. Wilcox to march his division six miles north to Hopewell Gap (another pass through the mountains), turn Ricketts’ right flank, and then get to his rear, possibly cutting off any escape route. Simultaneously, Lee ordered Colonel Henry Benning’s brigade to scale Pond Mountain, to the south, and turn Ricketts’ left flank. As evening approached, Ricketts found himself in danger of being surrounded. After skirmishing near Chapman’s Mill, Ricketts fell back to Gainesville and then to Manassas Junction, assuring Longstreet’s soldiers safe passage through the gap.
The Battle of Thoroughfare Gap was a relatively minor engagement that had significant consequences. Combined losses on both sides totaled only about 100. Nonetheless, the Confederate victory created a clear path for Longstreet’s rendezvous with Jackson’s forces near Manassas Junction on the evening of August 29. The reunification of the Army of Northern Virginia virtually cinched a Confederate victory at the Second Battle of Bull Run the next day.