In a horse society, there is a pecking order. The dominant horse controls the other horses by biting or kicking. Ultimately, the dominant horse merely threatens the other horses and they move out of the way. The pecking order determines who eats or drinks first. The pecking order is enforced aggressively when challenges are made. When a horse is aggressive to humans, it means that they are or intend to be the dominant party in the relationship. The size of the horse makes this a very dangerous situation. You must demonstrate your dominance and not allow the horse to be aggressive toward you. Start in a round pen with something you can move the horse with, such as a stick with a bag on it, rope or whip. Move the horse around the pen until it becomes submissive (put its head down, licks its lips, wants to stop). Step in front of the horse occasionally to change direction and enforce your control. You may need to get aggressive to enforce your authority. Any time the horse shows a negative attitude with its ears, actions, etc., chase it off to establish control. After you have established your dominance, bring a feed bucket into the round pen and alternately let the horse eat a bite and then drive it off and make it work. In a short time, the horse should be waiting for you to allow it to eat. Remember that in the horse's world, kicking and biting are normal acts to establish dominance. You may have to use the whip to establish dominance and develop a safe human/horse relationship.