Our recently adopted Great Dane and our old terrier went at it. Got them separated fairly quickly with no serious damage, but then tried to put the Dane on his back in a submissive posture. It looks so easy when the Dog Whisperer does it My wife was hopping around saying "Don't let him win!" and I was saying "Feel free to jump in and help!" Finally got him down and calm, but it sure didn't happen easy. Here's a pic so you can imagine wrestling a dog with a head the size of a bear's.