Really sorry to hear about the incident. A dog fight is a scary, stressful and potentially very dangerous event. I dealt with this as a daily event when I was living in Los Angeles and training my dog in public parks and hiking him in the mountains. It seemed like almost every Los Angeleno believed not only that their dog should be free to run off leash, but that the rest of us should be thrilled to let our dogs "play" with theirs. Of course, there were dog fights all the time and being the person with the intact male was not a treat.
I learned to warn people ahead of time when they looked like they wanted to set their dog towards me for "play time". I told them, "please put your dog on a leash, mine is not friendly". The not friendly part was key to any sort of compliance. Many seem to need to believe that their dog will be injured before they leash them up. Of course, a warning is no good for a dog without an owner, like the one you encountered.
I also learned to listen intently for the sound of incoming dogs. That usually helped on hikes or in the neighborhood where the line of sight was poor. That may have helped in your incident. Also, watch your dog. You may not hear the chow coming, but he will certainly be listening, especially after this most recent incident. If you see him start posturing, put him down and get in front of him, in the direction he is indicating. (see below for more about this)
If a dog was obviously coming for a "play session" I put my dog on a down and stepped about 10 feet in front of him towards the incoming dog. At this point I either chased them off or caught them, depending on how aggressive they actually were. A sweet dog is usually easy to catch and there's no reason to scare them by chasing them. But, the ones that really wanted to get to my dog to challenge him I scolded or yelled at or lunged at until they ran away. It's really pretty easy to keep them off your dog if he holds his down. And, putting him on the down does a lot to deflate incoming dogs. He can't posture or stimulate the other dog much while he is down. I rarely had any trouble chasing them off. If I could tell they were really coming for blood, I pulled out whatever I had on me to use as a "weapon" to threaten them more. There were only a few that I ever had to kick to keep off my dog. The majority really give up very easily when they see they are going to have a pretty big fight on their hands.
Using this method, I never had a single dog fight, though I had quite a few fun training sessions ruined by nasty dogs and even nastier owners who thought they were entitled to break leash laws and harass me. The only time one of my dogs was attacked, I was hurrying to get ice for a friend with a broken finger and not paying attention to the nasty chow lying behind the hot dog cart. I came with my puppy on a leash to ask for ice and the chow was on top of him before I could do anything.
I've never tried the bear spray- it just seems to likely to back-fire on you. Has anyone here actually used it?
As for breaking up a fight once it has started, there is nothing as good as a whiffle ball bat full of pebbles- learned that from a good old time horse guy. The whiffle ball bat smarts on contact but won't do any serious damage and the rocks make a really scary noise. Combine that with crazy erratic swinging and I think you could breakup most dog fights. I have used that one with success when I had two males get together by mistake (the kennel I was working at kept one handy).
Good luck!
She doesn't handle strange dogs well at all.
