I have grown up with a mixture of cats and dogs all my life, different ones arriving on the scene at different times.
What I've learned is this:
1-) When introducing a new one to the family it is much easier if one of the parties is a young'un (kitten or puppy). Whichever is the younger one, will accept the other as the dominant much easier than if you threw two adults together. Yes, dogs can let cats be the boss. I've seen it many times :lol:
2-) Next, declaw the cat. PLEASE. Nothing is sadder than a blind animal. And dogs.. well... I love'em, but they're just plain stupid:lol: One of my dogs was blinded in one eye by a cat, during the introduction phase. At the very least, take the cat to the groomers and have his claws cut to the shortest possible. OR get them capped with the rubber caps if your groomer has them. At least until the worst of the territory battles are over.
3-) Introduce them slowly. Keep one in a carrier, while the other sniffs it out. Then let them loose. 1hr at a time. Seperating them now and then for them to be able to 'relax' on their own. Gradually increasing their time together.
4-) They will fight it out. Over a few months. Accept this, and understand that it is NATURAL. Be it two cats, two dogs, a cat and a dog. This is a territory thing and how they will determine who is the boss. Now, granted, you should interfer in some fights. But, if they're not getting hurt, let them go at it. Let them decide who the boss is. The sooner that decision is reached, the happier they will be.
I've had a mishmash over the years. In time, all mypets got on famously, sleeping together, playing together.. It does work out. In some cases, it happens fast, in others, it takes a while. You just never know. I had one cat that took as long as 12mths to sort things out. BUT it has sorted out and now both he and my dog will sit with me at the same time.
Fights become less and less frequent, and they become more and more tolerant of the new arrival in 'their space'.
Hope this helps
:hug: