Being an avid petstore trainer/walker, Strauss and I have often come into contact with the "beligerent" dog. My first instinct and action is always to tell my dog to platz (lie down).
Why?
#1 This puts my dog in a more submissive position , which allows the other dog to calm down somewhat in 98% of these "altercations"
#2 It gives me a chance to get BETWEEN myself and the other dog (Yes, I risk bites to protect my dog)
#3 It gives me one less dog to deal with!
#4 If a dog happens to jump/lunge at my dog, he lands on my dog's BACK and doesn't get his FACE, and I get to catch the other dog (again, yes, I risk a bite to protect my dog...that's my job)...in some situations the dog completely jumps OVER mine (Yes, it has happened).
#5 Strauss has a good enough watch that if it is a LARGE dog, I can bring him back up to fuss, focus on the OTHER dog, and keep him watching ME so things don't get worse.
This is NOT to say that we are in dog/dog altercations every other day, but they happen...that's what happens when you take your dog out in the world. Sometimes there are altercations.
Man, I can't get his CDX, but he obeys where it really counts, I can tell you that....