This is something they have to figure out on their own. Ripley is becoming a mature male and he is trying to establish his position in the hierarchy of the house. The younger one is always going to challenge the older one for position and unless the older one is very old, frail or ill, it won't roll over and give in so easily.
I'm assuming both are neutered, if not you need to start there.
A couple things you can do...keep their nails clipped, maybe use Soft Paws for a while until things calm down. Use Feliway atomizers, they contain synthetic calming pheromones. If Ripley tends to do sneak attacks, put a bell on him so Squirt knows where he is at all times. When you see Ripley thinking about starting something...distract him, give him some attention. I know it goes against the grain to reward him when you know he was thinking about being a jerk...but it actually works (I have the same problem with Kobi beating up on Maggie).
BTW...in your title, you used the description Cat vs Cat...have you read the book by that name? If not, I'd really recommend it. I learned quite a bit from it.
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Holly, Misty & their friend, Jake, the dog.
Onyx, Callie May, Maggie & Kobi forever in my heart.
Yes, I know I need a new signature pic...someday...