Working Dogs - BRT characteristics (Lengthy but excellent)
BRTs were designed to protect people and places as well as to help with other tasks in a combat situation. That is going to lead to a different set of natural behaviors than is going to be seen in a breed that is designed primarily for companionship. These dogs are bred first for the task and then for companionship. If you look at the descriptions of the history of the breed the companionship didn’t even factor in until the breed was placed in civilian hands. A companion dog is not going to act aggressively with out extreme provocation. A working dog is going to have a much lower threshold for aggression.
Black Terrier from Russia - this is a very ambiguous dog. They say that once upon a time there was an old Russian breed of this type. But as we could see, this ancient breed in any case could not be a founder of the black Terriers.
the Nature of this dog is ambiguous. Gifted with an innate sense of protection, it can be very energetic and determined in the work, and at the same time in the family - a calm and very gentle companion.
The Black Russian terrier is a very modern dog and most definitely a dog with a purpose. It's conception was far from accidental, rather it was conceived out of necessity in order to produce a dog that combined and improved upon the positive aspects of several other breeds whilst excluding their negative or less desirable traits.
A good way to understand the Black Russian terrier is to know it's history. A history as fascinating as the breed is impressive.
BRTs were designed to protect people and places as well as to help with other tasks in a combat situation. That is going to lead to a different set of natural behaviors than is going to be seen in a breed that is designed primarily for companionship. These dogs are bred first for the task and then for companionship. If you look at the descriptions of the history of the breed the companionship didn’t even factor in until the breed was placed in civilian hands. A companion dog is not going to act aggressively with out extreme provocation. A working dog is going to have a much lower threshold for aggression. 
