Gen Mclellan has been villified over the many years as doing too muich "dithering". He was clearly very tardy folowing Gen Lee, after the battle at Anteitam/Sharpsburg..
He surely did not follow up very well.. The old axiom.."when the foe is running..press him all the harder', did not seem to be in Mcllelan's repetoir.
Pres Lincoln even showed up at his Anteitam encampment, to encourage hin to pursue the fight. Some armchair theoriticians even suggest that had Mclellan pursued vigorously, the war could have ended right there. I rather doubt that, but it would have had a very different result than delay did.
Pres lincoln suggested that Mclellan's performance was 'like an old lady trying to shoo geese across a creek'.
Some "armchair generals" seem to think that had Mclellan pursued with full vigor, that could have ended the war very soon.
While I disagree with that conclusion, surely a vigorous pursuit would have had a very different result than did dithering.
We must not underestimate the overall toughness of the confederate army..the toughest foe the US ever fought !
Recent investigations seem to point to logistics being the age old vexing problem.
https://www.historynet.com/mcclellan-did-he-have-the-slows-or-a-supply-crisis/ https://warfarehistorynetwork.com/article/the-rocky-relationship-between-abraham-lincoln-and-george-b-mcclellan/#:~:text=When%20McClellan%20failed%20to%20aggressively,tick