Originally Posted by Shrike
I doubt Shanks beat Kaidou, he most probably only made him retreat just by showing up. Kaidou (or anyone for that matter) wouldn't risk fighting another Yonkou (even if Shanks was weaker then he is, and we all know he isn't) because losing many if not all of his forces for a goal which isn't nearly worth it would be ludicrous. He just wanted to grab the spoils of war for free basically, but when Shanks showed up he just pulled back, like anyone would do.
That would be a pretty good scene to visit at some point in the future to see what happened in that encounter prior to Shanks arriving at Marineford. Because it was mentioned that the WG were shitting their pants at a possible team-up between Whitebeard and Shanks, that would have tipped the scale of the balance of power and Kaidou intercepted Shanks probably for that same fear.
“Pirates are evil? The Marines are righteous? These terms have always changed throughout the course of history! Kids who have never seen peace and kids who have never seen war have different values! Those who stand at the top determine what's wrong and what's right! This very place is neutral ground! Justice will prevail, you say? But of course it will! Whoever wins this war becomes justice!”
― Donquixote Doflamingo