Elijah Viers White had grown up near Leesburg and recruited his battalion of Confederate cavalry from the Loudoun farms and villages where he had spent his life. The men called themselves the Comanches and earned a reputation for hard riding and harder fighting. By September 1862, White preferred to be with Lee's army in Maryland - his native state was Maryland, and he saw the campaign as a chance to recruit. He got in an altercation with J.E.B. Stuart at Frederick, however, and Stuart ordered him back to Virginia. Robert E. Lee, hoping to smooth things over while supporting his cavalry commander, gave White a useful assignment: escort Colonel Reuben Lindsay Walker's artillery battalion from Point of Rocks across the Potomac into Loudoun by way of Lovettsville and Hillsboro, then up onto Loudoun Heights to anchor the southern jaw of the trap Lee was setting at Harpers Ferry. White did the job. Then he settled back into the partisan operations he ran in his home county whenever the army did not need him.

While the Battle of Antietam raged on September 17, Lieutenant Colonel Hugh Judson Kilpatrick was already moving to reoccupy Leesburg with ten companies of Federal cavalry. He found the town held by a handful of Confederates - one company of the 6th Virginia Cavalry, about forty infantry under Captain Gibson, and Colonel White with thirty of his own troopers. Gibson wanted to retreat without a fight. White, defending the streets he had grown up on, convinced him to stay. The fight that broke out near the courthouse was brief. In retaliation for the resistance, Kilpatrick ordered up his artillery and shelled the town. The damage is disputed - Confederate accounts described significant destruction, while Kilpatrick claimed he had only fired a few rounds over the rooftops - but the Confederate force pulled out west along the Winchester Pike. As they retreated, the 10th New York Cavalry caught them at the edge of town. White led a charge and was severely wounded. His men carried him to Harmony - now called Hamilton - and Kilpatrick took Leesburg.

With White recovering from his wounds, command of the battalion fell to First Lieutenant Frank Myers. On October 16, Stonewall Jackson's quartermaster ordered Myers to round up cattle from the Lovettsville area to feed the Army of Northern Virginia. Myers tried and was blocked by General John R. Kenly's Maryland infantry and cavalry. In response, a small scouting party under John DeButts - later a Mosby Ranger - was sent to harass Kenly, and harass him they did, driving the Federals back to Harpers Ferry. With Kenly gone, Captain Treyhorn assumed the area was safe and set out on October 19 with a scouting party toward Berlin, Maryland - the present-day town of Brunswick. He bedded down for the night at Lovettsville. The Federals had been watching. General Geary marched out of Harpers Ferry with two infantry brigades and 300 cavalrymen of Colonel Thomas Devin's 6th New York to find him.

On the morning of October 20, Geary's advance guard captured Treyhorn's pickets and the Confederates began falling back toward Wheatland. At Hillsboro, Geary split his force in two. He sent Devin and the 6th New York east along the Charles Town Pike to Wheatland, then north up the Berlin Turnpike. Geary himself took his infantry up the Mountain Road, which ran parallel to the Berlin Pike, before turning east toward the village of Morrisonville. At the Glenmore Farm just outside Morrisonville, the two prongs of the Federal advance closed on Treyhorn at the same time. Devin charged the front. Geary's infantry hit the flank. Treyhorn's men were caught in the open. He ordered his sharpshooters to climb onto a pair of haystacks and fire down at the advancing Federal infantry, which they did with enough effect to slow the attack briefly. It was not enough. The 35th broke, the retreat became a rout, and the chase ended only when the horses of the 6th New York were too blown to keep going. The Comanches lost one killed, two wounded, and twenty-one captured. Treyhorn was forced to resign and leave the company in disgrace. Eight days later, on October 28, Colonel Bradley T. Johnson formally organized the company into a battalion: the 35th Battalion of Virginia Cavalry. Within a year the unit would be one of the most feared mounted commands in the Confederacy. Glenmore Farm was a stumble at the start of a long ride.