Attack submarine

An attack submarine or hunter-killer submarine is a submarine specifically designed for the purpose of attacking and sinking other submarines, surface combatants and merchant vessels. In the Soviet and Russian navies they were and are called "multi-purpose submarines".^[1] They are also used to protect friendly surface combatants and missile submarines.^[2] Some attack subs are also armed with cruise missiles, increasing the scope of their potential missions to include land targets.

Attack submarines may be either nuclear-powered or diesel–electric ("conventionally") powered. In the United States Navy naming system, and in the equivalent NATO system (STANAG 1166), nuclear-powered attack submarines are known as SSNs and their anti-submarine (ASW) diesel–electric predecessors are SSKs. In the US Navy, SSNs are unofficially called "fast attacks".