In June 1863, as Gen. Robert E. Lee led the Army of Northern Virginia through Blue Ridge gaps to the Shenandoah Valley, Maj. Gen. J.E.B. Stuart’s cavalry screened the army from Federal observation. The Union cavalry chief, Brig. Gen. Alfred Pleasonton, dispatched Brig. Gen. David M. Gregg to penetrate Stuart’s screen. On 17 June, Gregg ordered Col. Alfred A.N. Duffie to reconnoiter from Aldie to Middleburg. Duffie drove off Confederate pickets there, alerting Stuart. Duffie withdrew south of Middleburg, but Brig. Gen. Beverly H. Robertson’s brigade surrounded and almost wiped out Duffie’s command before it escaped the next morning.