On June 21, Union cavalry made a determined effort to pierce Stuart's cavalry screen. Hampton's and Robertson's brigades made a stand at Goose Creek, west of Middleburg, and beat back Gregg's division. Buford's column detoured to attack the Confederate left flank near Upperville but encountered William E. "Grumble" Jones's and John R. Chambliss's brigades while J.I. Gregg's and Kilpatrick's brigades advanced on the Upperville from the east along the Little River Turnpike. After furious mounted fighting, Stuart withdrew to take a strong defensive position in Ashby Gap, even as Confederate infantry crossed the Potomac into Maryland. As cavalry skirmishing diminished, Stuart made the fateful decision to strike east and make a circuit of the Union army as it marched toward Gettysburg.