When I was reading this, my thought was that this dog sounds like a terrier. I just recently lost my precious little Jack Russell Terrier. She got quite old & had the problems that got with it. The point is that she was always aggressive to other animals back when I took her for walks. I always restrained her & later she was pretty much restricted to indoors. I loved & miss that little dog, but she did have certain undesirable traits. A person getting a dog for the first time needs to be aware of some of this.
I had a half Llaso Apso that liked to start fights behind fences. Although, if the dog or cat in question got behind the fence to take up her challenge, she’d run away as fast as she could.
It was tempting, sometimes, to want to throw her over the fence so she can meet the dog that she was trying to challenge.