Project 971 Щука-Б (Shchuka-B, 'Shchuka' meaning pike, NATO reporting name "Akula"), is a nuclear-powered attack submarine (SSN) first deployed by the Soviet Navy in 1986. The class is also known under the name Bars (eng. snow leopard). There are four sub-classes or flights of Shchuka, consisting of the original seven "Akula I" submarines which were commissioned between 1984 and 1990, six "Improved Akula" submarines commissioned between 1991 and 2009, one "Akula II" submarine commissioned in 1995 and one Akula III commissioned in 2001.[citation needed] The Russians call all of the submarines Schuka-B, regardless of modifications.