GETTYSBURG, Battle of, the most im portant event of the American Civil War and the turning point in the long and stubbornly fought contest.
Preliminary Campaign.— After the battle of Chancellorsville (q.v.), 1-3 May 1863, the opposing armies resumed their positions on the Rappahannock, Lee's army on the south side of the river, at Fredericksburg, Hooker's on the north side, opposite. Encouraged by victory, and desiring to relieve Virginia of the presence of the Union army, Lee determined to transfer the seat of war north of the Potomac. His army, 1 June, was composed of the three corps of Longstreet, Ewell and A. P. Hill, and Stuart's cavalry force of 12,000 men, in all about 76,000, with 190 guns. Hooker's Union army was composed of seven corps, the First, commanded by Reynolds; Second, by Hancock; Third, by Sickles; Fifth, by Meade; Sixth, by Sedgwick; Eleventh, by Howard; and Twelfth, by Slocum; aggregating, 10 June 82,000 in fantry and artillery "present for duty and equipped," with 410 guns, to which were added Pleasonton's cavalry force of about 12,000.
Lee began his campaign 3 June by sending Longstreet and Ewell to Culpeper Court House, where the cavalry, under Stuart, was also con centrated. A. P. Hill remained at Fredericks burg to watch and detain Hooker. Hooker suspected Lee's movement and, under his direc tion, Sedgwick laid bridges, crossed the river, and reported that Lee's main body seemed to be still there. Pleasonton was ordered to feel the position at Culpeper. Reinforced by two infantry brigades, he crossed the Rappahannock on the morning of the 9th, encountered Stuart at Fleetwood and Brandy Station (see FLEET