Less than two weeks after the start of the Gettysburg Campaign, Maj. Gen. J.E.B. Stuart’s cavalry successfully screened the Confederate infantry as it marched north behind the sheltering Blue Ridge Mountains. The Union Cavalry Corps commander, Brig. Gen. Alfred Pleasanton, ordered forward the division of Brig. Gen. David McMurtrie Gregg to penetrate Stuart's screen. The probing Federals of Brig. Gen. Judson Kilpatrick’s cavalry brigade, in the advance of Gregg’s division, encountered Col. Thomas T. Munford’s Virginia cavalry troopers near the village of Aldie in the Bull Run Mountains. At Aldie, two turnpikes led west to Ashby's Gap and northwest to Snickers Gap, while the Carolina Road, a strategic north-south transportation route, was located just to the east. A furious fight erupted, at first in favor of Munford as Federal charges were stopped and forced back by the withering volley of sharpshooters behind stone walls. The 1st Massachusetts Cavalry was trapped in a blind curve on the Snicker's Gap Turnpike and was nearly destroyed, losing 198 of 294 men. Kilpatrick gained strength with reinforcements in the afternoon, so Munford withdrew westward toward Middleburg where the battle would continue the next day. Aldie was one in a series of small battles along the Ashby's Gap Turnpike in which Stuart's forces successfully delayed Pleasonton's thrust across the Loudoun Valley, depriving him of the opportunity to locate Lee's army.