The breed standard describes the Dobermann as a dog of medium size that is also strong and muscularly built. Although they are considered to be working dogs, Dobermanns are often stereotyped as being ferocious and aggressive. As a personal protection dog, the Dobermann was originally bred for these traits: it had to be large and intimidating, fearless, and willing to defend its owner from attackers (especially other guard dogs), but sufficiently obedient and restrained to do so only on command. These traits served the dog well in its role as a personal defense dog, police dog, or war dog, but were not ideally adapted to a companionship role. The Dobermann's aggression has been toned down by modern breeders over the years, however.