Wild horse stallions must constantly fend off other males that are compelled to challenge and overtake the position of dominant herd leaders. Usually, a confrontation is low-key, with the challenger facing off with the herd stallion, then turning away casually or sprinting away from the bared teeth of the more aggressive leader at his rear end. Only rarely does the challenger stand up to the powerful herd stallion and assert himself. As the stallions rise up on their hind legs, each tries to strike the other with thrusting front hooves. Although most of the blows are ducked and even blocked, a hoof strike that lands on the face of a fighting horse emits a loud crack; it's got to hurt.
Keeping watch for an entire day with a long lens at the ready is difficult, but worth the wait when the battles escalate to the point demonstrated in this frame.