Wolves rely on intimidation to cause their prey to flee, then they flank, attack, and take down in pursuit. You can see them keep trying to set this up and they might have if it was one dog (the wolf moves in on the dog which flees towards the camera). The mastiff is bred to stand its ground and charge to intimidate as well but are also bred to actually get into a scrap as well. This leaves the wolves strategy completely beat and forces their own retreat. Pretty cool to see unfold.