Not much can stop a horse that is set on running. But you know what a "ground hitch" is? Well, you control a horse with a bridle and usually a bit. When you get off the horse, you tie the reins of the bridle to something, a hitching post, a fence rail, a tree, whatever. If you don't have something solid to tie the horse to, and the horse is well trained, you can just drop the reins to the ground. That's right, a horse, powerful as he is, can be held in place just because the reins are touching the ground. Elephants are used as bulldozers in some parts of the world.
