My dog Spatz, was an American Staffordshire Terrier. I don't have a picture of her because she lived in the 80's.
Anyway Spatz looked just like a vicious Pit Bull but she wasn't. She was brindle in color with white spots on all her feet. Hence the name Spatz. She weighed about 60 pounds.
Spatz was so well mannered that she was the poster dog of well behaved canines. She never barked uncontrollably and would shut up when given the command "Shut Up." She knew all the doggie commands, heel, fetch, shake, sit, stay, lay down, come here, let go, and more. She was a very smart dog. She even growled on command.
Spatz got along with everybody and everything. She never chased cat's (or squirrels or possums). She never fought with other dogs. Spatz never barked when other dogs in the neighborhood did.
When introduced as a friend she would obey that friend as well as myself. BUT if you weren't introduced properly she was very protective.
One time I came home from work and found a window forced open, the screen cut and the side door was open. Someone tried to break in and steal from me. And there was Spatz sitting by the open door inside the house protecting it. She wouldn't go out of the house, unless I said it was okay. I taught her that because before that she would rush the storm doors so hard she broke the glass, once. Fortunately she was unhurt but the glass was shattered.
As mentioned above I taught Spatz to growl on command. Sometimes when I got in from work I would have her growl for me. She thought this was great fun because then I would let her out.
I imagine when the thief came in there was Spatz growling at him. He didn't know the command to go out so she stayed there growling until he went out. Nothing was missing from the house. The thief was caught 2 weeks later.
Moral of this story is training my dog to only go out when I said it was okay (even if the door was open) saved me from getting ripped off. Now that was a cool dog.