In the ANIME, it was mentioned that before coming to marineford, Shanks clashed with Kaido pirates. How come Shanks and crew were able to survive the war with Kaido pirates without being much damaged?
There is a speculation, but no official source, that no war actually happened. Kaido was going to stop Whitebeard from goving to Marineford, but Shanks stopped Kaido from doing so instead. What some people think, is that Shanks merely stood in his way. If had been a war, then it must have been mentioned. I could be, maybe, that Kaido tried to start something and sent some people stir up something but Shanks stopped them. In that case, Kaido would not go to war with Shanks because:
- Kaido is a pirate, so he obviously wanted to kill Whitebeard when he had the chance at that point,
- He had a chance. That was the fact that Whitebeard was not ready for battle with someone else meant that a surprise attack could do him serious damage and make him late for Ace. In Shanks' case, red hair was ready for Kaido. That meant that a war much worse than all of Marineford battle would happen. Kaido was not ready for that. In other words, when Shanks stopped the ships (like I said that was a guess) Then Kaido backed off knowing that this was not the time.
That said, the same reason could explain why the Yonkou don't have fights everyday with each other. They would wear down, all 4, too soon for the marines to stop them.