Redoutable-class submarine (1928)  The "Redoutable"-class submarines were a group of 31 submarines built between 1924 and 1937 for the French Navy. Most of the class saw service during the Second World War. The class is also known in French as the "Classe 1 500 tonnes", and they were designated as "First Class submarines", or "large submarine cruisers". They are known as the "Redoutable" class in reference to the lead boat , in service from 1931 to 1942. The class is divided into two sub-class series, Type I, known as "Le Redoutable" and Type II, "Pascal". Modern submarines when they were designed, they quickly became outdated, and were approaching obsolescence by the beginning of the Second World War. The conditions of the Armistice of 22 June 1940 prevented the Vichy government from carrying out a modernization programme. 24 out of the 29 units that served in the war were lost. Used in the defence of the Second French colonial empire under the Vichy regime, submarines of the class saw action against Allied offensives at the Battles of Dakar, Libreville and Madagascar. Many of the submarines of the class came under Allied control after the Allied landings in North Africa. Few however saw much further active service after this due to a period of refitting and alterations done in the United States between February 1943 and March 1945. One exception was , which took part in the liberation of Corsica. The surviving submarines were largely used for training purposes after the war, with the last of them being disarmed in 1952. The Washington Naval Treaty of 1922 sought to prevent a future naval arms race by imposing limits on the number and size of certain types of warships that each great power could possess. France sought to expand its submarine forces – which were not limited by the treaty – as an essential tool to defend its coastline and empire. The 1100-ton s, designed in 1922, was the initial attempt to meet these requirements; however, the speed of the submarines was notably insufficient and the design overall was considered inferior to the last German submarines launched in 1918. The design for the "Requin" class's successor was commissioned from general engineer of maritime engineering Léon Roquebert. Roquebert was tasked with creating a "grand cruiser" type of submarine, with the role of carrying out surveillance of an adversary's bases, destroying their communications by attacking their ships, while protecting French colonies. They were operate with a surface squadron and provide clearance of enemy vessels for it.