American Civil war but both sides fight in the best way possible

Basically what the title says, how would the ACW have looked like if both sides had fought without committing the major strategic and tactical errors they did in OTL.
The only rule in this thread is that the Civil war need to still happen, ofc you can make It shorter or longer.
Question is if the North is willing to pay the bill. Both sides playing the wargame perfectly would imply a lot better estimation of the likely butcher's bill on both sides. Given that better estimation, both sides are far more likely to lose their nerve.