Not sure what to do exactly either, but I can add that it is generally not a good idea to step in between two dogs feverishly going at it. Use a broom or some extension of you hands to separate them as when they are in fight mode, they are usually indesciminate about what/who they bite.

My dogs are doing the same thing. But mine are much smaller. You don't know us (PTrs ) yet, but my Bob is a Terrier and a Terror. He is also Mentally Unstable (Not Really). He is always picking fights and will not back down. Trouble is Ginger will only take so much and then she tears into Bob. They seem to go in waves. I did notice that they have been good for a long time. And then my wife brought Pig Ears home from the Petstore. This seems to set Bob off. He thinks he owns all Pig Ears in the World. He can have 10 himself and he will want the 11th Ginger has.

As long as the Pig Ears are around - not even in sight or in use - he is in the bullying stage, and is always looking around guardedly. If I go to pet Ginger, he comes flying over.

We got rid of the Pig Ears and it has been a couple of days. Bob is starting to realize that they are no where to be found and ironically, he is starting to calm down and letting his guard down.

So, maybe if you have anything that could be considered "private property" by any of the two - deny them both it and establish yourself as "the one and only ALPHA".