Two male gelded horses battling for the position of alpha within the herd. Thank goodness they were over a fence line. One of the powers of this play/roughness is to see who will move their feet away from the other horse while they could get bitten. Whoever moves their feet first, loses. The alpha horse always moves the other horse's feet in a backward submissiveness. In this particular photo, the winner is the blue roan on the right.