Have you ever seen men getting "attacked" by a police or military dog as part of the dog's training? The men (I've never seen a woman, but I'd like to think there are some strong, feisty women who suit up for this role) wear either just a big padded thing on one of their arms, or they're engulfed entirely in a padded suit.
The dog lunges for the padded arm, and the "victim" can't do squat while this occurs.
So from the man's point of view, what is this all like? According to an article on indefinitelywild.gizmodo.com, a 125-pound Military Working Dog named Fritz "attacked" the author who was wearing a "heavily padded safety suit" that included a "rubber prosthetic arm."
He was instructed to hold out his arm while Fritz sat obediently. The dog was given orders by a handler to clamp onto the author's arm. The 150-pound author had no control over his body being thrashed about. The goal is to prevent the dog from biting up and down the arm, which the author was not able to do.
The dog instantly released his "victim" upon hearing commands. The author was then told to "say something mean to the dog and then run away" to "provoke him." So the author said "Profane-you Fritz!" and bolted.
Fritz bolted after him "at full speed, in anger." Now let me interject here. I question that the dog was angry. A human might be if you said something mean, but not a dog. I'm no dog expert, although Ive had 2 German Shepherds in the past 2 years, but it's fair to suppose that the combination of tone in the author's voice, and his sudden sprinting away, kicked up Fritz's instinct to charge after prey. This is why dogs run after a tossed ball.
The author was brought to the ground in an instant. Fritz remained clamped onto him as the handlers escorted him and the dog towards some spectators. Fritz was rewarded with just a pat on the head (but hey, maybe to a dog, that's serious stuff).
I've always wondered what this is like from the dog's point of view. If the dog was truly in attack, shred-him-up mode, wouldn't he go for the face instead of clinging on to just a padded arm that tastes like rubber and not live flesh? When people are attacked by dogs while jogging, walking or inside their homes, almost always, they receive injuries (sometimes very serious) to the face and scalp, even neck. Such dogs will also often tear out chunks of the victim's legs.
But police or military dogs in training always go after that big rubber arm-and stay with it. To a degree, the dogs think it's just a game, especially since sometimes, the "victim" is the dog's own handler-who in the next scene is lovingly interacting with the animal.
Anyway, most dogs are a great layer for home protection no matter their size or abilities. Clearly some dogs aren't, but, if it is remotely territorial it can act as an additional set of eyes and ears. And if the dog barks upon hearing an intruder, it can act as a layer added to an alarm system.