Despite strong Union resistance on the second day of the battle, Lee believed that his troops had almost achieved victory.  One more push, he thought and the Union troops would break.  Lee believed that Union commanders had thinned out the center of their line to reinforce Cemetery Hill on their right (Day 1) and Little Round Top on their left (Day 2).  So on Day 3, he ordered Longstreet to attack the center of the Union line. 

The above photo shows the Union position along Cemetery Ridge in the foreground.  The starting point of the Confederate attack was the wood line in the distance which is nearly two miles away.  After a 2 hour artillery barrage, 14,000 Confederate troops marched out of that tree line and across the open field, all the while under withering Union fire.  The Confederates did make it to the stone wall at the spot in the photo – the place that became known as “the high water mark” of the Confederacy – but more than half of them had already become casualties and the attack failed. 

Both armies were devastated by the casualties that were incurred over the three day battle.  That night, Lee quietly retreated and slipped back into Virginia.  The commander of the Union Army, General George Meade, spent the evening preparing for another Confederate attack.  Once he realized the Confederates had left, he decided his army was too spent to pursue.  This infuriated President Lincoln who felt that an aggressive pursuit and attack of Lee at this point would have ended the war.  Instead, the Civil War went on for two more years, but from July 3, 1863 onward, the Confederate Army was always on the defensive.