My mom is an ER doctor in the city, where she gets cases smaller hospitals can't handle. A couple days ago, she had a patient come in that hand a serious hand injury. The woman said she didn't know exactly what happened, just that two horses were fighting and she was reaching for the halter on one of them.
When her injuries were evaluated, this is what they found. Index and middle finger had been bitten off. Ring finger had been degloved, and had to be amputated. Two metacarpals were fractured. Ulna was fractured. Teeth marks more than half way up her elbow.
The point of this thread is to reinforce the idea that horses are bigger and stronger than humans. Do not risk serious injury to yourself to stop two horses from fighting. They can handle it a lot better than you can.