Operation Ring ( Operatsia Koltso; Oghak gortsoğut'yun, meaning Chaykend operation) was the codename for the May 1991 military operation conducted by Soviet Internal Security Forces and OMON units in the northern regions (Shahumyan, Shusha, Martakert and Hadrut) of Nagorno-Karabakh Autonomous Oblast of the Azerbaijan SSR and in a number of bordering regions of the Armenian SSR (Noyemberyan, Goris and Tavush). Officially dubbed a "passport checking operation," the ostensible goal launched by the Soviet Union's internal and defense ministries was to disarm Armenian militia detachments that had been organized in "[illegally] armed formations." The operation involved the use of ground troops who accompanied a complement of military vehicles, artillery and helicopter gunships to be used to root