The Boxer is part of the Molosser dog group, developed in Germany in the late 19th century from the now extinct Bullenbeisser, a dog of Mastiff descent, and Bulldogs brought in from Great Britain. The Bullenbeisser had been working as a hunting dog for centuries, employed in the pursuit of bear, wild boar, and deer. Its task was to seize the prey and hold it until the hunters arrived. In later years, faster dogs were favored and a smaller Bullenbeisser was bred in Brabant, in northern Belgium. It is generally accepted that the Brabanter Bullenbeisser was a direct ancestor of today's Boxer. In 1894, three Germans by the names of Friedrich Robert, Elard König, and R. Höpner decided to stabilize the breed and put it on exhibition at a dog show. This was done in Munich in 1896, and the year before they founded the first Boxer Club, the Deutscher Boxer Club. The Club went on to publish the first Boxer breed standard in 1904, a detailed document that has not been changed much to this day. The breed was introduced to other parts of Europe in the late 19th century and to the United States around the turn of the 20th century. The American Kennel Club (AKC) registered the first Boxer in 1904, and recognized the first Boxer champion, Dampf vom Dom, in 1915. During World War I, the Boxer was co-opted for military work, acting as a valuable messenger dog, pack-carrier, attack dog, and guard dog. It was not until after World War II that the Boxer became popular around the world. Taken home by returning soldiers, they introduced the dog to a wider audience and soon became a favorite as a companion, a show dog, and a guard dog.
The German citizen George Alt, a Munich resident, mated a brindle-colored bitch imported from France named Flora with a local dog of unknown ancestry, known simply as "Boxer", resulting in a fawn-and-white male, named "Lechner's Box" after its owner. This dog was mated with his own dam Flora, and one of its offspring was a bitch called Alt's Schecken. George Alt mated Schecken with a Bulldog named Dr. Toneissen's Tom to produce the historically significant dog Mühlbauer's Flocki. Flocki was the first Boxer to enter the German Stud Book after winning the aforementioned show for St. Bernards in Munich 1896, which was the first event to have a class specific for Boxers.
The white bitch Ch. Blanka von Angertor, Flocki's sister, was even more influential when mated with Piccolo von Angertor (Lechner's Box grandson) to produce the predominantly white (parti-colored) bitch Meta von der Passage, which, even bearing little resemblance with the modern Boxer standard (early photographs depicts her as too long, weak-backed and down-faced), is considered the mother of the breed. John Wagner, in The Boxer (first published in 1939) said the following regarding this bitch. Meta von der Passage played the most important role of the five original ancestors. Our great line of sires all trace directly back to this female. She was a substantially built, low to the ground, brindle and white parti-color, lacking in underjaw and exceedingly lippy. As a producing female few in any breed can match her record. She consistently whelped puppies of marvelous type and rare quality. Those of her offspring sired by Flock St. Salvator and Wotan dominate all present-day pedigrees. Combined with Wotan and Mirzl children, they made the Boxer.