What prerequisites must be in place before introducing counter-canter?

Counter-canter is a collection and balance exercise that requires a solid foundation before it can be introduced productively, and attempting it before the prerequisites are confirmed reliably produces a horse that breaks to trot, swaps leads, or becomes tense and resistant rather than developing the benefits the exercise is meant to provide. The first prerequisite is confirmed, willing lead departures on both leads from the walk and trot. If a horse cannot reliably pick up the correct lead on request, it has no foundation from which to hold a specific lead in counter-canter. The lead must be the rider's choice before the counter-canter exercise makes sense to ask for. The second prerequisite is the ability to maintain a balanced, self-sustained lope on a large circle on both leads without swapping, breaking, or requiring constant rein management. A horse that cannot hold the correct lead on a gentle circle is not ready to hold the counter-lead through a corner. The demands of counter-canter are greater than those of normal correct-lead canter work, and the horse must be confirmed in the easier task before the harder one is reasonable to ask. The third prerequisite is basic response to lateral leg aids at the lope. In counter-canter, the rider uses specific leg positions to signal and maintain the counter-lead — the outside leg at the cinch and the inside leg slightly behind to hold the haunches from falling in. A horse that does not yet yield to leg pressure at the lope will not respond to these maintenance aids clearly enough for the counter-canter to be executable. Clinton Anderson suggests a practical test: if the horse can lope a large circle on the correct lead on a loose rein, maintain its lead through three direction changes at the walk, and yield its hindquarters softly from leg pressure at the lope, the prerequisites for beginning counter-canter introduction are in place.