The Doberman is a comparatively recent dog breed, originally bred in the 1880s and 1890s in Germany.
Than man who created the breed was Karl Friedrich Louis Dobermann, a tax collector, dog fancier, and the night watchman at the local pound in Apolda, Germany. He needed a dog that would serve as a protector and intimidator while he was performing his duties, and he decided that his best bet was to create his own breed. He collected a number of dogs from the pound, including Rottweilers and Greyhounds, although perhaps not purebreds; there is speculation that Dobermans also contain some Weimaraner, German Shorthaired Pointer, Manchester Terrier, and German Sheepdog (a predecessor to our modern German Shepherd).
He wanted a dog that was bold and brave, agile and alert, and also one that met his personal aesthetics. He valued the look and attitude of the terriers, but needed a larger, more intimidating dog. He was, obviously, successful, and his breed was originally known as Dobermann's Dogs. After his death this was changed to Doberman Pinscher, pinscher being a German word for terrier; the pinscher has since been dropped.
Dobermann died in 1894, before the modern form of the Doberman was set. His breeding work was continued by Otto Goeller, a local kennel owner. He not only brought the breed much closer to its current form, but also worked to promote interest in the breed. He started the first Doberman breed club in 1899, the National Dobermannpinscher Klub.
Dobermans nearly went extinct during the first world war, as many European dog breeders were unable to feed their dogs during times of shortage, and many dogs starved or were put down. The breed was saved due to two factors; their service in the German military, and a number of breeders sending their breeding stock to more protected countries. The later was an important factor in spreading the Doberman onto the international scene, including across the Atlantic into America; suddenly the Doberman was no longer a German breed, but an international one. The dog's service in both the first and second world wars gained them the (temporary, in retrospect) name of Soldatenhunds.
The Doberman's popularity took off in the 1970s, particularly in America, perhaps in part due to a number of movies staring them, primarily in villainous roles (The Doberman Gang, The Daring Dobermans, The Amazing Dobermans). Their popularity has waned since that time, but their military and theatrical history has left them with reputations as violent and dangerous dogs, a reputation that is largely baseless.