The fiercest fighting of the battle—and the second bloodiest day of the Civil War—occurred on May 3 as Lee launched multiple attacks against the Union position at Chancellorsville. That same day, John Sedgwick advanced across the Rappahannock River, defeated the small Confederate force at Marye's Heights in the Second Battle of Fredericksburg, and then moved to the west. Confederate forces succeeded in militarily delaying Union forces in the Battle of Salem Church.