Great dogs. We had a Schutzhund trained "Warlock" Doberman for years. It seems the bigger the dog, the shorter the lifespan. Dammit... 
Police Dogs are trained in German. Most gangbangers don't speak English all that well, let alone German.
Unfortunately the words for "attack" and "heel" are similar, LOL!
They are amazing dogs. Very loving with family, obedient and if a stranger even pretends to try and trespass into your property, they are on a deathwish. These dogs also have a ferocious bark. In the dead of night, you hear them go off and it's like the hounds of hell, downright scary.
The bullmastiff is on another level all together. While they are not too vicious looking, nor is their bark as ferocious as the Doberman, their sheer size/strength alone and aggressiveness is incredible. You want your kids to be well protected as they play in their backyard, let the bullmastiff run around with them.
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