I would not consider Nagorno-Karabakh a "breakaway" region. It has been a part of Azerbaijani Soviet Socialist Republic while USSR existed, but upon USSR collapse this region declared independence just the same as Azerbaijan itself. To this end it has never been of contemporary Azerbaijan state and therefore did not "break away" from it. Moreover, it withstood deadly war that Azerbaijan waged on it in the 90s and defended its independence from Azerbaijan on a battle field. It should not be considered part of Azerbaijan and for that reason any military actions of Azerbaijan against Nagorno-Karabahk is an open act of aggression.