Akoula class submarine Project 971

The Akula class, Soviet designation Project 971 Shchuka-B are a series of nuclear-powered attack submarines (SSNs) first deployed by the Soviet Navy in 1986. There are four sub-classes or flights of Shchuka-B, consisting of the original seven Project 971 boats (codenamed Akula I), commissioned between 1984 and 1990; six Project 971Is (Improved Akulas), commissioned between 1991 and 2009; one Project 971U (Akula II), commissioned in 1995; and one Project 971M (Akula III), commissioned in 2001. The Russians call all of the submarines Shchuka-B, regardless of modifications.