The history of the Boxer breed dates back to before 1939. There were dogs in Munich, Germany, then, but the Germans were not breeding dogs. According to John Wagner, writer of the book on the history of the Boxer Breed, the type of dog that was around from the time of the Assyrians, more than 2000 B.C. These dogs were heavy set and used in war.
From these war dogs, the Bullenbeisser was bred. In England, the Mastiff was produced and later crossed with the faster hounds to get the Englisch Dogge, known as the Great Dane.
Most of the German dogs used for hunting were big dogs with heads like wolves and were known as ‘Rüden’. Some were smaller but could hold down prey because of their strength. The smaller Bullenbeisser bred in Brabant is considered the ancestor to today’s Boxer.
During the Napoleonic war, the dogs became the dogs of butchers and cattle dealers and won over many people with their intelligence and sweet nature. As far as it could be discerned, they were without any white marks on their fur. With the influx of dogs from England, some natural crossbreeding took place between Boxers and Bulldogs, which produced dogs with white markings.
Owners started looking to create dogs without some undesirable traits by selective breeding. The Boxer club formed in Munich in 1895 already drew up a Boxer Standard guide that had many points still used today.
More extensive information about the breeding and development of Boxers can be found from the American Boxer Club on the internet.