Shanks and Whitebeard meet on the Moby Dick, while the Straw Hat Pirates recovers from fighting on Enie’s Lobby in Water 7.
Even as Shanks enters the ship, he collapses most of Whitebeard’s gang with his haki. He then sits down in front of Whitebeard and the two begin a conversation. In the process, Shanks tries to convince Whitebeard that he should call Ace off. He says that he knows Ace is strong, but he has no chance against Blackbeard. Shanks doesn’t just say this, because he knows what he’s talking about, he had the scars on his face from a fight with Blackbeard.
Whitebeard, however, only replies that he won’t let Shanks tell him anything, and attacks Shanks with his naginata, which Shanks deflects with his sword, whereupon even the sky splits. So these two must have tremendous power to pull off something like that.
