What country was last involved in submarine warfare?

US submarines launched weapons during the Iraqi war. In warfare against enemy ships, the British submarine Conqueror torpedoed and sank the Argentine cruiser General Belgrano in the Falklands War in 1982. Rather than hunt for the Conqueror, two Argentine destroyers rescued survivors from the General Belgrano. The Brits had two other subs in the war zone, but they missed a chance at the Argentine carrier Vienticinco de Mayo which (with her destroyers) turned back upon hearing that their cruiser had been sunk, and a sea battle between the two navies was thus avoided.