A coach dog is a breed of dog that was historically used as a watchdog and for protection, as well as to run alongside coaches. The most common synonym for coach dog is Dalmatian, but there are other breeds that were used for this purpose, including the Bull Terrier and the Boxer. These dogs were trained for the specific task of running alongside coaches, ensuring that they remained safe from robbers and other dangers on the road. The coach dog was an important part of travel during the 18th and 19th centuries and continues to be a beloved breed today.