French submarines of World War II The French submarine fleet of World War II was one of the largest in the world at that time . It saw action during the World War II , but had a chequered service history due to the complications created by France ' s position during the war . During the conflict , 59 submarine s , over three - quarters of its total strength , were lost . Construction history . After World War I France had a fleet of 36 submarines , in a variety of classes , plus 11 ex - German U - boats ; these were mostly obsolescent ( all had been disposed of by the 30 ' s ) and she was interested in replacing them . To this end the French Navy made plans for a fleet of vessels in three Types : Type I ocean going / grand patrol ; Type 2 coastal defence ; Type 3 mine layers . At the same time , the major powers were negotiating an arms limitation treaty at the 1922 Washington Naval Conference . Whilst there was discussion of banning submarines altogether , and to outlaw their use ( a course favoured by Britain ) both France and Italy opposed this . However the conference did place restrictions on the number and size of warships of various types that nations could build . The ocean - going submarine was restricted to a 1500 ton surface displacement , while the coastal submarine was limited to 600 tons , though there was no limit placed on the numbers of these vessels that could be built . In 1922 - 23 France ordered the " Requin " class , a Type 1 submarine . These ran to 9 vessels , but their indifferent performance led to calls for an improved design . This came in 1924 with the " Redoutable " class , a successful design , which ran to 31 vessels in three series . In 1923 the French Navy placed orders for a series of coastal / seagoing Type 2 boats . The order was placed with three different design bureaux , which led to three different designs to the same specification . Known collectively as the 600 Series , these were the " Sirène " , " Ariane " and " Circé " classes , a total of 10 boats . They were followed in 1926 by the 630 Series , another three classes from the same bureaux . These were the " Argonaute " , " Orion " and " Diane " classes , a further 16 boats . In 1934 the Navy opted for a standardized Admiralty design , the " Minerve " class of 6 boats , and in 1939 by the " Aurore " class , a larger , much improved version of the " Minerve " . And further enlarged design , the " Phenix " class , were ordered but not built , due to France ' s defeat in 1940 and the subsequent armistice . The type 3 minelayer was represented by the " Saphir " class , a 1925 order for 6 boats . These were followed in 1937 by the " Émeraude " class , but again these were not built before the 1940 armistice . France also experimented with the concept of the submarine cruiser , in common with other navies of the time . In 1926 she built the " Surcouf " , for many years the largest submarine ever built . However the vessel had little role to play in French naval stategy , and the experiment was not repeated . Thus in 1939 France had , in total , a fleet of 77 submarines , making it the fifth largest submarine force in the world at that time . Design features . Whilst being designed by different bureaux , the French submarines of this period shared a number of features . They were generally double - hulled , with an emphasis on good surface handling , though this led to them being indifferent divers . They also emphasized habitability , needing to be suitable for service in France ' s colonial empire , which could mean long voyages and operations in the tropics . One unique feature was the use of external torpedo mounts . As well as torpedo tubes in the bow and stern , most French submarines carried torpedo tubes externally in trainable mounts , built into the outer casing . These could be trained to fire at various angles beyond fore and aft , but could not be re - loaded at sea . French submarines also mounted torpedoes of different calibres , typically carrying the 400mm ( 15 . 75 inch ) torpedo , for use against " soft " targets such as merchant ships , as well as the 550mm ( 21 . 7 in ) torpedo for use against warships . Service history . The role of the French submarine force in 1939 was to act in concert with the French fleet and with France ' s allies against the Axis powers , with particular responsibilities in the Mediterranean . It also operated in defence of France ' s overseas territories and colonial empire . This changed in 1940 with the fall of France and the signing of the armistice with Germany . One submarine had been sunk in action , and several others scuttled to prevent their capture ; seven others , in British ports at the time of the armistice , became part of the Free French naval force ( FNFL ) . However the majority remained under the control of the Vichy government . Over the next two years 16 subamarines were lost in Vichy service , mostly in clashes with British and Allied forces . In November 1942 , with the invasion of Vichy territory by the Germans , many of the remaining vessels were scuttled , or captured by the Axis . Those that survived , or managed to escape , joined the FNFL ; despite losses , and with replacement from allied navies , France ended the war with 20 submarines in service , having lost 50 boats from a variety of causes . Classes . Type 1 grand patrol / ocean - going submarine Type 2 coastal / sea - going submarines Type 3 minelayer submarines Cruiser submarine In addition , Free French forces operated " Curie " , a British built U - class submarine .