In decades past, before we as a culture became more responsible about keeping our dogs safe at home, a fenced yard was a relatively rare phenomenon. The family dog was often allowed to roam the neighborhood and interact freely with other neighborhood dogs and humans. In general, they were better socialized and fence aggression was uncommon. Of course, dogs also routinely got hit by cars, shot, poisoned, and just plain disappeared. I am certainly not advocating going back to the days of free-roaming dogs just to avoid fence-fighting! But we do need to look for better ways to keep dogs contained in order to avoid concomitant unwanted behaviors.