It can be a problem i know as my cut nearly lost an eye and was sliced across his tummy on one occasion. He was neutered and im pretty sure the other cats were to. It didnt even seem to matter male or female. I tried all sorts also to stop them doing it but to no avail.
I did find alot of the fights my cat was involved in were at night or early hours so we got into the habit of getting our cat in when we went to bed. Some times though it was with a bit of bribs i.e. chicken. I also use to be worried cars wouldnt see him at night even with his reflectors on his collar.

Cats can be so territorial but hopfully with time they may tollerate each other.
I dont really know what to say as cats will be cats and they can be fickle as to whom they want to share there spaces with neutered or not.