(“. . . moving the girth around the inside front leg.”)
“Why should I learn turn on the forehand? It’s not in any test.” The reason is more political than academic. Remember at one point leg yielding was also banned from American tests. Depending on the philosophical underpinnings of the system of riding you follow, turn on the forehand can mean a of variety of things. Not all of them are created equal.
Historically in the German tradition, turn on the forehand was done from the halt and practiced simply as an obedience-oriented, moving away from the leg exercise very early in the training. Once accomplished, it was soon abandoned for more sophisticated lateral displacement requiring back to front connection starting with the shoulder-fore.
The teachers who most influenced me—Lindgren, Sommer, Wikne, Ljungquist, Nathhorst, Christiansen—taught in the Scandinavian tradition (as illustrated in the the Danish cavalry manual) where leg yielding and turn on the forehand were viewed quite differently.
The first few times a horse was invited to move off the leg were similar to what was described above. However, a more meaningful and useful version of the exercise once the horse understood moving over, was to think of keeping him straight with a slight poll positioning to the inside away from the direction of movement, and rather than moving your pushing leg behind the girth, leaving it at the girth and moving the girth around the inside front leg. The rider’s outer leg stayed back to keep the haunches in line, and if the horse wanted to back off the bit, take backwards steps, or fall out, the outer leg behind the girth reminded him to think forward and into the hand. In the learning phase the horse was permitted to “turn around the forehand” rather than being on the spot, just as introductory turns on haunches are done on a smallish circle. As the exercise progressed, the size of the circle was made smaller, but the horse still maintained the rhythm in the turn, staying straight, and willing to move forward off the leg instantaneously when requested.
This requires the rider to develop a much more sophisticated interaction among the aids which has many applications to more advanced work. The results of the coordination of the pushing/receiving/allowing/momentarily redirecting effects are immediately visible by the horse’s responses. Learning to ride the movement step-by-step and tailoring the size of the aids to what the horse needs at the moment helps the rider get beyond generic, recipe riding. The results are obvious when a pupil can master it!.