During the Night of 1 July, powerful components of the Army of the Potomac reinforced the battered forces which had suffered defeat at Gettysburg during the day. On 2 July they occupied a strong defensive position; strong until Sickles advanced III Corps without authorization to an exposed salient on the Union left. The Confederate attacks on 2 July rolled over Sickles and almost captured the key high ground of Little Round Top. The desperate, but ultimately successful, defence of first Little Round top and later Cemetery Hill, compelled Lee to stake everything on a charge the next day against the Union centre. Text by James Arnold and Roberta Wiener.