How do I get my horse to turn on the haunches?

The turn on the haunches is a foundational lateral movement in western and classical horsemanship that asks the horse to pivot his forehand around his hindquarters — specifically around his inside hind leg, which acts as the pivot point while the horse moves his front end through an arc of ninety, one hundred eighty, or three hundred sixty degrees. In western performance it is the foundation of the spin and the rollback. In classical work it is a stepping stone to pirouette. In everyday riding it is one of the most practically useful movements available — the ability to turn in a tight space, to position the horse for a specific task, or to redirect without requiring forward movement. The prerequisites for a correct turn on the haunches are more specific than they might appear. The horse must understand and respond promptly to the lateral leg aid — specifically the leg behind the girth that moves the hindquarters and the leg at the girth that creates the bend through the horse's body. He must understand and respond to the direct rein and the indirect rein independently enough that the rider can direct his forehand with the opening rein while containing his forward movement with the outside rein. A horse that has correct leg yields, a correct turn on the forehand, and basic lateral bend established has the foundational vocabulary the turn on the haunches requires. Begin teaching the turn on the haunches from the walk rather than from a halt, because the walk provides the impulsion and the natural leg swing rhythm that allows the inside hind to step correctly in place. Ask the horse to walk forward quietly, then use the opening inside rein to invite the forehand to step to the inside while the inside leg at the girth maintains the bend and the outside rein contains the horse's forward movement without blocking it entirely. The outside leg behind the girth guards the hindquarters from stepping out of the pivot. The horse should take one or two steps of the front legs around the inside hind before the movement is released and the horse is asked to walk forward again. The inside hind leg is the specific focus of the quality assessment in any turn on the haunches. In a correct turn on the haunches the inside hind leg steps actively in rhythm — lifting, placing, and lifting again in the same beat as the other legs rather than being stuck or dragged — and it remains approximately in place rather than stepping backward, which would indicate backing rather than pivoting, or stepping forward into the circle, which would indicate a larger movement than intended. The progression from one or two steps to a full quarter turn, half turn, and eventually a full turn should be gradual and based on the quality of what the horse offers rather than an ambitious plan to complete the full movement in early training sessions. A few high-quality steps of correct movement are worth infinitely more than a full rotation of compromised quality, and the horse that is consistently asked for only as much as he can offer with correctness develops both the understanding and the physical capacity for the full movement over time.