Its generally accepted that Lee's incursion into Maryland was a play to garner the the support of the Southern loyalists there and gain a lot of new recruits. Had he won at Antietam he felt he would've been seen as a liberator freeing MD from Yankee oppression and that was supposed to result in waves of goodwill from the locals. As it was he dropped his battle plans and ended up leaving the battlefield non victorious. I believe the war was totally winnable right up to the third day at Gettysburg. The North was becoming war weary.
Agreed. Lee made a bad call and unfortunately, it was a really bad call at a pivotal moment. Ewell not taking Cemetery Hill was a huge missed opportunity.
