If he hadn't met Talissa, Robb would've still been the same. No mercy for the Lannisters. Until she met Talissa, Robb really spared a scout for the Lannister just to sent them a message. That's a big risk if you ask me. But despite all of that, Robb Stark somehow manages to win against Tywin in all 3 battlefields. While Tywin hasn't won any that he gathered his council as to how they can defeat Robb Stark. That's very rare to happen because in the books, Tywin has always been the commander and he usually knows how to beat his enemy but in this war he needed some advise. It shows how smart Robb Stark truly is. Mistakes I think could've been prevented by Robb to win the war. 1. He met Talissa. 2. He refused to marry one of the Frey's daughters because he was in love with Talissa. Robb Stark thought they were going to be all ugly but Frey was leaving the most prettiest daughter as a reserve for someone like Robb Stark to marry her. If he hadn't refused to that proposal I think the Starks will still have a chance since the Freys control the riverrlands and the Lannisters wouldn't be able to go pass through the North if the Freys control that and the Starks are their allies. Robb could've literally just married one of Frey's daughter and still stay with Talissa. But instead, the Starks always have this "honor" thing. *That honor, being honorable, got all of them killed.*
