The 1863 Battle of Gettysburg stopped Robert E. Lee's second invasion of the North. It was the deadliest battle of the Civil War, with over 50,000 casualties during the three day battle, a scale of suffering never seen before or since in America. The Union won victory and had new life injected into its war effort. The Confederacy saw its best chance at striking a deadly blow against the North and demoralizing them slip away.