When I was a kid, we had a pure bred German shepherd, that was definitely a guard dog, and there was little if any training on our family’s part. One time a city worker with a rake and a shovel approached my Dad and yelled at my Dad, and the dog jumped over the fence and grabbed the man’s arm. I understand he broke his skin. We had to let the vet keep him for a week, but he didn’t have rabies or anything else. He just let that worker know in no uncertain terms not to act that way with my Dad.
Double ditto that. My parents had GS and it would stalk around at a night protecting the home.