From the eternally-rewarding Ranch Life and the Hunting-Trail, by Theodore Roosevelt.
No matter what you may think of TR, you’ve gotta admit the man could write.
The best and quietest horses on the ranch are far from being those broken by the best riders; on the contrary, they are those that have been handled most gently, although firmly, and that have had the greatest number of days devoted to their education.
Some horses, of course, are almost incurably vicious, and must be conquered by main force. One pleasing brute on my ranch will at times rush at a man open-mouthed like a wolf, and this is a regular trick of the range-stallions. … A wild stallion fears no beast except the grizzly, and will not always flinch from an encounter with it; yet it is a curious fact that a jack will almost always kill one in a fair fight.
The particulars of a fight of this sort were related to me by a cattle man who was engaged in bringing out blooded stock from the East. Among the animals under his charge were two great stallions, one gray and one black, and a fine jackass, not much over half the size of either of the former. The animals were kept in separate pens, but one day both horses got into the same enclosure, next to the jack-pen, and began to fight as only enraged stallions can, striking like boxers with their fore feet, and biting with their teeth. The gray was getting the best of it; but while clinched with his antagonist in one tussle they rolled against the jack-pen, breaking it in. No sooner was the jack at liberty than, with ears laid back and mouth wide open, he made straight for the two horses, who had for the moment separated. The gray turned to meet him, rearing on his hind legs and striking at him with his fore feet; but the jack slipped in, and in a minute grasped his antagonist by the throat with his wide-open jaws and then held on like a bull-dog, all four feet planted stiffly in the soil. The stallion made tremendous efforts to shake him off; he would try to whirl
round and kick him, but for that the jack was too short; then he would rise up, lifting the jack off the ground, and strike at him with his fore feet; but all that he gained by this was to skin his foe’s front legs without making him loose his hold. Twice they fell, and twice the stallion rose, by main strength dragging the jack with him; but all in vain. Meanwhile the black horse attacked both the combatants, with perfect impartiality, striking and kicking them with his hoofs, while his teeth, as they slipped off the tough hides, met with a snap like a bear-trap. Undoubtedly the jack would have killed at least one of the horses had not the men come up, and with no small difficulty separated the maddened brutes.
— Chapter III, The Home Ranch
The particulars of a fight of this sort were related to me by a cattle man who was engaged in bringing out blooded stock from the East. Among the animals under his charge were two great stallions, one gray and one black, and a fine jackass, not much over half the size of either of the former. The animals were kept in separate pens, but one day both horses got into the same enclosure, next to the jack-pen, and began to fight as only enraged stallions can, striking like boxers with their fore feet, and biting with their teeth. The gray was getting the best of it; but while clinched with his antagonist in one tussle they rolled against the jack-pen, breaking it in. No sooner was the jack at liberty than, with ears laid back and mouth wide open, he made straight for the two horses, who had for the moment separated. The gray turned to meet him, rearing on his hind legs and striking at him with his fore feet; but the jack slipped in, and in a minute grasped his antagonist by the throat with his wide-open jaws and then held on like a bull-dog, all four feet planted stiffly in the soil. The stallion made tremendous efforts to shake him off; he would try to whirl 
round and kick him, but for that the jack was too short; then he would rise up, lifting the jack off the ground, and strike at him with his fore feet; but all that he gained by this was to skin his foe’s front legs without making him loose his hold. Twice they fell, and twice the stallion rose, by main strength dragging the jack with him; but all in vain. Meanwhile the black horse attacked both the combatants, with perfect impartiality, striking and kicking them with his hoofs, while his teeth, as they slipped off the tough hides, met with a snap like a bear-trap. Undoubtedly the jack would have killed at least one of the horses had not the men come up, and with no small difficulty separated the maddened brutes.
We have wild horses a couple hours west of Salt Lake; when domestic horses run loose and try to join them, it can get pretty wild. The mares are accepted, but stallions and geldings are killed or chased off by the herd stallion.