[1] It requires the horse, while bent in the direction of the turn, to move his forehand around his hindquarters so that he makes a very small circle with the inside foreleg.
Additionally, the horse should continue to display basic requirements of dressage, such as an even and regular rhythm, relaxation, acceptance of the aids, balance, and freedom of movement.
If the rider asks for too much too soon, it is likely that the horse will begin to lose important qualities as the turn proceeds, such as rhythm, bend, or activity behind.
The outside leg prevents the hindquarters from swinging out, the outside rein maintains a correct bend to the inside, and helps to regulate the driving aids, telling the horse to turn rather than walk forward.
If the horse steps backward, the rider should apply more inside leg, and may need to decrease the restraining aids.