Stallions fight for mares and territory, and these two have been going at it all day. One of them is a couple miles away from his normal range, and the other is defending his large harem of mares. This is a serious fight, but it is a normal, healthy, and important part of wild horse behavior. It's how the healthiest, strongest genetics prevail. And in this case, if the intruding stallion wins it will likely introduce genetic diversity to his new territory. Fights like these can go on for days at