The Inflexible (S 615) is the sixth and final of the Redoutable class SNLE ("Sous-marin Nucléaire Lanceur d'Engins", "Nuclear Missile-Launching Submarine") of the Force océanique stratégique (FOST), the submarine nuclear deterrent component of the French Navy. Construction began on 27 March 1980. She was launched on 23 June 1982, commissioned on 1 April 1985 and decommissioned on 14 January 2008. Inflexible uses basically the same design as the other Redoutable-class vessels, but has benefited from technological advances over its predecessors: