Battle of Chantilly

(Wikipedia) The Battle of Chantilly (or Ox Hill, the Confederate name) took place on September 1, 1862, in Fairfax County, Virginia, as the concluding battle of the Northern Virginia Campaign of the American Civil War.
... The fighting was tactically inconclusive, but Jackson's turning movement was foiled and he was unable to block the Union retreat or destroy Pope's army. Two key Union generals were killed. Pope, recognizing the attack as an indication of continued danger to his army, continued his retreat to the fortifications around Washington, D.C.. Lee began the Maryland Campaign, including the Battle of Antietam, after Pope retreated out of Virginia. The Army of the Potomac, under Maj. Gen. George B. McClellan, absorbed the forces of Pope's Army of Virginia, which was disbanded as a separate army. Continued