What were Bullmastiffs bred for?

What were Bullmastiffs bred for?
Bullmastiffs were originally bred in England during the 19th century by gamekeepers to help guard estates and hunt down poachers. They are a cross between Bulldogs and Mastiffs, combining the strength, speed, and endurance of both breeds. 
The primary purpose of the Bullmastiff was to quietly track and overpower poachers without mauling them; they were trained to pin down intruders and hold them until the gamekeepers arrived rather than attack aggressively. This unique skill set made Bullmastiffs highly valued for their ability to protect large estates and game reserves.