I dont know the exact timeline but a while before the Marinefold incident and the execution of Ace, it was stated that Shanks went ahead to battle Kaido "THE KING OF BEASTS"
Was the battle an "all-out war" between Kaido and shanks fleet? Or more of a 1v1 between the 2 Emperors.
Also, since Shanks made it to Marinefold immediately after battling the King of Beasts, does that imply that Kido lost the fight? I'm really intrigued because the fact that Shanks showed up while Kaido didn't means that Shanks was able to prevent Kaido from running amok in Marinefold. Could this testament prove that Shanks is way stronger than Kaido?