When I still lived in the city and walked my dogs in off-leash areas, I would carry a walking stick. I had a nice stout oak walking stick with a brass handle that I would carry on such outings. I had to use it twice on other dogs that attacked my dog. It's amazing how quickly an aggressive dog will change his mind and ki-yi back to his master when whacked across the snout with it.
And you can tell some dogs have already felt the sting of a walking stick. Just raise it up, and they know to keep their distance.
