Wow... things are obviously much worse than you thought. Mine went at it a couple of times pretty good, but never drew blood. Ironically, Ginger (Older Beagle) always whipped Bob (newer Terrier-like pup) but ultimately gave up and has assumed the submisssive role with Bob taking over as Alpha.

As far as I could see Bob never "won" a fight, but Ginger really grew tired of the constant challenges and pretty much now says (with her demeanor), "WHATEVER".

Don't know the answer to your dilemna. There have been lots of posts on similar situations in the past. Some try and slwly wean the dog of aggressive behavior towards others by having then constantly tethered to their person - trhat way they can control and alter their every move. Good luck.

P.S. A forget, maybe you can update your update... Older dog is what??? and newer smaller is also a what breed???