Does it Ring a Bell?

Ok, I've long forgotten the name of a book I read and I need some help finding the title: 

I read this maybe 30 years ago. but to be safe lets say somewhere between 1986 and 1995, but probably right in the middle of that span. 

Science fiction paperback, average length. I don't recall anything about the cover. 

There are two planets, neither one Earth, existing in the same solar system; one might have actually been the moon of the other. 

One of the globes is filled with human colonists, the other with a race of bipedal deer-like creatures that are our equal in intelligence. The two sides go to war. At some point the protagonist becomes a POW and develops a quasi-friendship, or at least a mutual respect, with the warden. This was NOT a children's book; at one point a POW caught raping his fellow inmates is dispatched by the protagonist with the wardens approval. 

Any ideas?