Ordered to disrupt Confederate plans for an anticipated offensive, General Alfred Pleasonton led the Army of the Potomac's cavalry corps in a two pronged attack across the Rapphannock River in the early morning hours. General J.E. B. Stuart's cavalry was taken unawares and a massive mounted action ensued with around 20,000 horsemen involved in close combat with sabre and pistol. After a ten hours of fighting, Pleasonton's troopers broke off and recrossed the river, ending the largest cavalry battle ever fought in North America. (By John Osborne)