The North Sea Fleet (NSF) is one of three fleets of the People's Liberation Army Navy. It includes nuclear-powered submarines: five Han class attack submarines and China's single Xia class submarine ballistic missile submarine, all based at Qingdao. The NSF has historically received primacy during the allocation of the destroyers and frigates, as its role was to be coastal defence of north east China (including Beijing) against any amphibious attacks by Russia. However, unlike the East and South Sea Fleets, it has never been involved in combat.