What is counter-canter and why is it trained as a lead change prerequisite?

Counter-canter is deliberately maintaining a canter lead that is opposite to the direction of travel — loping a circle to the left while on the right lead, or loping a corner to the right while on the left lead. It is called counter because it goes against the natural alignment of the horse's body with the direction of travel. Counter-canter is trained as a lead change prerequisite for several reasons that are well-established in both western performance and classical dressage training. First, it develops the horse's ability to maintain a specific lead regardless of what the direction of travel is suggesting, which means the lead becomes the rider's choice rather than the horse's automatic response to direction. A horse that cannot counter-canter does not yet have this level of rider control over the lead. Second, counter-canter develops the balance and self-carriage that flying lead changes require. Maintaining a counter-canter through a corner requires the horse to actively manage its balance without the natural physical support of being on the correct lead. This balance development directly improves the horse's ability to execute clean simultaneous changes, because the flying change also requires maintaining balance through a moment of significant physical reorganization. Third, counter-canter teaches the rider to control the horse's lead through specific aids rather than through positioning. The rider in counter-canter must actively maintain the wrong lead against the horse's tendency to swap to the comfortable lead — which develops precisely the aid clarity that flying lead changes require. Clinton Anderson and Pat Parelli both include counter-canter work in their lead change preparation, and classical dressage trainers consider it foundational preparation for the half-pass and tempi changes that appear at higher levels. The horse that can counter-canter correctly and confidently is a horse that is ready to learn the flying change.