Our newfie siblings would 'play' fight and you certainly didn't want to be in the middle of the clash of the titans (they ran toward each other and rose on their hind legs when they met with much ado). But sometimes they got ugly with each other over stupid things like rawhide bones that required intervention. I am not so stupid as to put myself between dogs that each outweighed me, but I have a very powerful "NO" voice when needed. It usually worked with them and almost always works now.
Sometimes it's useful for the human species as well.
