(This article is about 1991 Soviet conflict. For the last part of the Battle of Stalingrad, see Operation Koltso.) Operation Ring (Russian: Операция «Кольцо», Operatsia Koltso; Armenian: «Օղակ» գործողություն, Oghak gortsoğut'yun), known in Azerbaijan as the Chaykend Operation (Azerbaijani: Çaykənd əməliyyatı) was the codename for the May 1991 military operation conducted by Soviet Internal Security Forces and OMON units in the Armenian populated regions of Western Azerbaijan in the Lesser Caucasus mountains, the Shusha, Martakert and Hadrut regions of the Nagorno-Karabakh Autonomous Oblast, and along the northwestern border of the Armenian SSR in Noyemberyan, Goris and Tavush. Officially dubbed a "passport checking operation," the ostensible goal launched by the Soviet Union's internal and