The Battle of Brandy Station was the largest cavalry battle of the Civil War and the largest cavalry battle ever fought on the North American continent. It was also the first battle of the war's most famous campaign - Gettysburg.
The 1863 battle began at dawn as a raid, when 5,500 Union cavalry charged over the Rappahannock River in attempt to thwart an anticipated Confederate raid on Union supply line. But the Confederate army was actually on maneuvers, breaking camp to ride north into Pennsylvania.
The conflict quickly escalated to an all-out battle between to cavalries involving some 20,000 troops including 17,000 cavalry. Confederate General J.E.B. Stuart and the Union's John Buford basically fought to a draw. Although the Union advance was repelled, the overwhelming superiority that the Confederate cavalry once enjoyed was gone.