The South never intended to attempt the impossible and conquer the North. All they wanted to do was leave the Union.
All that the South needed to do was trap Abe in DC.
That's why Lee swang west then north then east, running into Buford at Gettysburg.
Buford rained on Lee's parade. He held up the Rebels until Union generals Reynolds and Meade could get there.
Then there was a heck of a fight.
Dumbazz Lee sent his Johnny Rebs directly into the face of the fire and got them butchered valiantly.
Game was over then. After that Grant was able to take over in the East and chase Lee all over Virginia until he finally cornered Lee like a rat.
The war was strictly strategic -- find the enemy & fix him in place & destroy him or his will to fight.