" How much of an effect on history can an animal have? A big one. Look at Alexander the Great’s horse Bucephalus, and “the little gentleman in the black fur coat” who’d killed King William the Third when his horse stepped in the mole’s front door. And Richard the Third standing on the field at Bosworth and shouting, “My kingdom for a horse! "

― Connie Willis , To Say Nothing of the Dog (Oxford Time Travel, #2)