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 sometimes erroneously called the "Bars" class, after one of its members. Note that Akula ("shark") is the Soviet designation of the ballistic missile submarine class designated by NATO as the Typhoon class submarine.
There are three sub-classes or flights of Shchuka, consisting of the original seven "Akula I" submarines which were built between 1982 and 1986, five "Improved Akula" submarines were built between 1986 and 1991, and four "Akula II" submarines were built from 1991. This information is disputed, however, as the distinction between the Improved Akula and the Akula II class is debated by authoritative sources. The Russians simply call all of the submarines Schuka-B, regardless of modifications, and it is rumoured that no two are alike.