Dog fights are pretty nervewracking. I've never had a problem with Tasha and Tommy because Tommy always immediately backs down and never fights back, but my two male collies had some scuffles when we first got Willie, and Cody was used to being the only dog. Thankfully there were never any injuries though and they settled after awhile and lived in harmony.

Tasha is used to being alpha now though and so I have to watch her closely if she runs into another alpha.