On the first day of the battle, leading elements of both armies met at Gettysburg, clashed, the North moved to the the high ground and the South failed to dislodge them.
At the beginning of the second day, Longstreet advised Lee to disengage and move towards Washington in order to look for better ground. Lee decided to stay, fight and took heavy losses for the next two days, losing the battle.
Longstreet’s advice looks a lot like the successful US approach in the Overland Campaign. Grant would attack, fix Lee, and then bypass him. Fixing looks a lot like a frontal attack, and against a foe of Lee’s and the pretended “army of northern Virgina”’s caliber, had to be made with substantial forces, and absent modern armor, suffer substantial losses.
Lee was asked what kind of reserve he maintained. “Not a regiment. If I pull anyone from the line he will break me, if I shorten the line he will turn me.
Looking carfully at Culp’s hill, you can see where US forces flanked the attacking insurrection forces. Not shown in the map is how Picket’s Charge was also flanked from both sides by US forces, so the large heavy bullets of the time could drill through two or more rebels as they walked up to the position they were to attack.