one o'clock before
When the sun rose over Gettysburg on the second day of July , the Union army , rushing breathlessly through the night to the rescue of its defeated advance corps , had reached the heights beyond the town . Before Longstreet had attempted to obey Lee 's command to take these hills , General Meade 's blue host had reached them and were entrenching themselves . The Confederate Commander discovered that in the death of Jackson , he had lost his right arm . It was one o'clock before Longstreet moved to the attack , hurling his columns in reckless daring against these bristling heights . When darkness drew its kindly veil over the scene , Lee 's army had driven General Sickles from his chosen position to his second line of defense on the hill behind , gained a foothold in the famous Devil 's Den at the base of the Round Tops , broken the lines of the Union right and held their fortifications on Culp 's Hill . The day had been one of frightful slaughter . The Union losses in the two days had reached the appalling total of more than twenty thousand men .