Under pressure to drive the Southern cavalry through Ashby’s Gap and locate General Robert E. Lee’s Army of Northern Virginia, Union General Alfred Pleasonton planned a two-front attack on June 19th. While General David Gregg’s division confronted J.E.B. Stuart’s cavalry west of Middleburg at Mount Defiance, General John Buford’s division swung around Middleburg in an effort to outflank Stuart and reach Snicker’s Gap, a route through which Lee’s forces were moving north through Berryville. Buford split his division, sending one brigade toward Middleburg and Pot House while the rest moved northwest from Aldie along the Snickersville Turnpike and back roads. After fighting Confederate skirmishers at Benton’s Bridge over Goose Creek, Buford’s brigades converged on Pot House, where they encountered elements of Colonel Thomas Rosser’s 5th Virginia Cavalry and the 7th Virginia Cavalry coming from Union. Ordered to avoid a full engagement, Rosser launched spoiling attacks that pinned Buford at the crossroads and hindered his movement toward Snickers Gap. As fighting continued into the evening, the sound of battle at Mount Defiance led Buford to send part of his force south to assist Gregg, including the Reserve Brigade of the 1st, 2nd, 5th, and 6th U.S. Cavalry. Moving south across Goose Creek at Millville and along Kirk’s Branch Road, these troops threatened Stuart’s left flank just as Stuart’s forces abandoned their position at Mount Defiance and reposted along the ridge to the west. Cavalry from both sides charged toward each other and met in a field north of the turnpike, where the clash ended in a draw behind two stone walls on a knoll. After exchanging scattered volleys, both sides were halted by a thunderstorm and spent a cold, rainy night in place. Rain on June 20th hindered major action, but on June 21st Federal probes and fierce fighting around Upperville brought the Aldie-Middleburg-Upperville cavalry campaign to its conclusion.