The only mistake that man made was not prosecuting the war in the north in the same manner as his counterpart did in the south. Had he burned/pilllaged/raped his way in and out, the story would likely have been different. Lee knew how to win battles, but he didn't understand what it takes to win a war.
The main mistake Lee made was even attacking the Union fishhook at Gettysburg at all. Longstreet was right. It didn't make sense
