I have a two year old GSD. We were walking along the sidewalk and there was another dog (jack russell terrier) unleashed on the person's front yard. The terrier ran to my dog and my dog sniffed the other dog and licked its face. The terrier snarled and snapped at my dog. In response, she snarled back and pinned the dog on the ground. The other dog yelped so I told my dog "leave it" and we continued walking. There was no teeth contact from either side from what I could tell.