Just a minor point -- "the Caucasus" includes more than just Georgia, Armenia, and Azerbaijan (sometimes collectively known as the "Southern Caucasus" or the "Transcaucasus"). It also regions of southern Russia -- including the volatile Chechnya, Ignushetia, Dagestan, and others -- which, along with some of the contested regions in the aforementione countries, are sometimes collectively known as the "Northern Caucasus" or "Ciscaucasus."

Regarding "Caucasus" versus "caucuses" -- talk to Anne Applebaum, she recently wrote an article in which she repeatedly substituted the latter for the former.