The First Day of the Battle of Gettysburg during the American Civil War took place on July 1, 1863, and began as an engagement between isolated units of the Army of Northern Virginia under Confederate General Robert E. Lee and the Army of the Potomac under Union Maj. Gen. George G. Meade. It soon escalated into a major battle which culminated in the outnumbered and defeated Union forces retreating to the high ground south of Gettysburg, Pennsylvania.The first-day battle proceeded in three phases as combatants continued to arrive at the battlefield. In the morning, two brigades of Confederate Maj. Gen. Henry Heth's division (of Lt. Gen. A.P. Hill's Third Corps) were delayed by dismounted Union cavalrymen under Brig. Gen. John Buford. As infantry reinforcements arrived under Maj. Gen. John F. Reynolds of the Union I Corps, the Confederate assaults down the Chambersburg Pike were repulsed, although Gen. Reynolds was killed.
