He was asserting his ownership of us. It was an infantile expression of dominance. The ferocious face that his father presented when he met Beau, was now becoming Beau's face. There was nothing I could do to change that. The dominant encounter can be expressed in terms of transactional analysis.
Dominance is a chip placed for life on certain dogs' shoulders.
The dominant dog will convince the less dominant dog to submit. Or violence may be necessary. They know of no agenda except pack order. Their instincts override their training, and they scrap. Both dogs begin in Puppy mode, demanding attention.