The first and most important thing to remember is when your dog is in the middle of a fight, they are not in their normal state of mind. They will not look at you as their master during this time but as another threat. The dog is in fight mode and that is all that is on their mind. The last thing you want to do is get in between them, that is a sure way to get bitten.
You can forget about yelling at them because that isn't going to break up a vicious fight between your German Shepherd and another dog. Don't hit them either, this may worsen things for the dogs as it will make them more angry and aggressive. You should never hit your dogs in any kind of situation whatsoever. Some people say throwing water on them helps but I haven't found this to work yet. Maybe it depends on the dog or the breed but I wouldn't recommend it.
I have two big dogs and they have been in a few fights. It's pretty scary when you have two large dog breeds against each other, it's very intimidating. I have found from my own research and personal experience that each dog needs to be picked up by their hind legs like a wheelbarrow and pulled away from each other. That is if you have two people there when the fight takes place. When using this technique, it causes the dog to concentrate on balancing on their two front legs so that they don't fall. If you pull back and direct them to the side like doing a circle in place this should seperate them and keep you out of harms way as well. This has worked every time for my dogs and hopefully it will work for you if you are ever in this unfortunate situation.
