I have 2 rescue cats in my household - both are kind of territorial (some days my house isn't big enough for the both of them) They have lived with us for 11 and 4 years. We are about to inherit a small chihuahua adult dog from my mother-in-law who just passed. She absolutely adores my husband, and presently lives in a house with several cats, having no issues with any of them. I am doing research now on the best way to get doggie settled into my house without either of my cats beating her up, or having a cat/dog war on our hands. I would appreciate any advice or process that works. I am really anxious about this going well -- I want harmony to remain in my house. She will be coming here to live soon. Thank you! Nise5280

I suggest barriers that can be removed over time.
A nice large crate/pen for the dog, with all the comforts of her old home in it. Put it near the center of your activity, and give her preference at night next to your bed, at least for a quite a while.
Bring her out to the couch with you for patting and playing, but have a cardboard box right at your feet to put her in, or that she can jump in.
Tossing treats to pets spaced apart often brings out good manners. As long as they stay in their spot, they get a treat tossed to them. If they spat, they don't.