What’s the best way to break up a dog fight at the dog park?
I don't know the best way but I'll say what I did earlier this year when a ~150lb cane corso attacked another person's a younger dog of the same breed (~120lbs, neither of them were mine). By the time I got over to them they were locked onto each other's faces and jerking their heads back and forth. The owners were useless in preventing damage -- blood was already smeared over the dogs. I applied a short blast of POM pepper spray at the combined dog face area and the combatants suddenly remembered they had better things to do like breathing and being able to see .
They recovered from the spray in a few minutes and the owners left the dog park, one would guess to the respective vets to fix the damage. And hopefully to schedule neutering for their intact males.
I assume I'll collect downvotes about this approach but it worked and didn't risk further damaging the animals. No regrets.