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.
Although these were modern submarines when they were designed, they quickly became outdated and were approaching obsolescence by the beginning of the Second World War.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.
Development
Context
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.
Construction of the Type I project submarines, starting with , was approved by the superior council of the navy on 1 July 1924. The building programme was expanded the following year with the Type II submarines. Together with the submarine cruiser , the Redoutable-class submarines constituted the elite of the French submarine fleet.
Characteristics long, with a beam of and a draught of , the Redoutable-class submarines could dive up to , although several, such as reached depths of while diving. The submarines had a surfaced displacement of and a submerged displacement of . Propulsion while surfaced was provided by two diesel motors for the Redoutable sub-class, while the Pascal variant boats had , while the submarines from Agosta onwards had , with a maximum speed of . Motors were built by the Swiss manufacturer Sulzer, with the exception of Pasteur, , Archimède, , , , , Persée and , which were propelled with Schneider motors. The submarines' electrical propulsion allowed them to attain speeds of while submerged. Designated as "grand cruise submarines" (), their surfaced range was at , and at , with a submerged range of at . Radio communication was through wireless antenna.
The Redoutable-class submarines had significant firepower. They were equipped with eleven torpedo tubes: four tubes in fixed positions in the bow, an orientable platform for three 550 mm tubes behind the conning tower, and another orientable platform on the stern composed of two 550 mm and two tubes. The 550 mm torpedoes were intended for use against large ships, with the 400 mm torpedoes for smaller boats. Torpedoes were propelled by compressed air at a speed of , exploding on impact. Torpedoes left a trail on the surface, which allowed the target to see and avoid the torpedo, as well as trace the torpedo back to its origin. The submarines were also fitted with a deck gun, mounted in front of the conning tower and from 1929, dual anti-aerial machine guns.
The Redoutable-class submarines had a quick diving speed, submerging in between 30 and 40 seconds. They had a reputation of handling well while at sea, both at the surface and while diving. Their motors were relatively noisy, as was auxiliary propulsion while submerged, and this constituted the principal criticism of these submarines, despite their reliability. Their speed and powerful armament was balanced against their ability to detect targets, which was essentially by visual sight. They were equipped with three periscopes – an attack periscope, a surveillance periscope, and an auxiliary periscope – and a hydrophone for passive sonar.
History Construction and early service
The large construction program made it necessary to contract work out to private shipyards, such as those at Caen or on the Loire, as well as the various naval bases. The construction orders were spread over six annual tranches. Small technical alterations were made to the design between orders, utilizing experience gained from previous batches. This did not prevent delays in delivery, which for some orders lasted up to two years and generated design disparities. This absence of standardization had consequences for the maintenance of the submarines, particularly during the Second World War. Laid down on 1 July 1925, the first submarine, Redoutable, was launched on 24 February 1928, and placed in service by 10 July 1931. The 31st and last of the series to be laid down, , entered service on 1 January 1937. Ouessant and were the last to enter service, on 1 January 1939, because of mounting delays at Cherbourg.
The submarines underwent substantial modifications throughout the 1930s, particularly regarding navigational abilities. They conducted training patrols and port visits in the Antilles, along the African coast or in Indochina. Two were lost in accidents before the Second World War: sank during trials off the Normandy coast on 7 July 1932, while was lost off Indochina on 15 June 1939.
Second World War First actions
At the beginning of Second World War, the Pascal-type vessels were divided between the First Navy Squadron at Brest and the Second Squadron at Toulon. They were assigned to operate with their respective squadrons, attack or capture enemy ships, and protect the Franco-British lines of communication. Two Redoutable-type boats were based at Cherbourg. Designed in 1920s, they were still reliable boats, but were becoming obsolete. They were vulnerable to attacks: their submerged propulsion systems were sensitive to bombardment, their maximum diving depth was limited and became insufficient during the conflict, and their underwater sound systems were weak. They formed 40% of the French submarine fleet, composed of a total of 77 naval vessels.
Between September 1939 and June 1940, the French submarines patrolled in the Northern seas and the Atlantic, particularly off the neutral ports of Spain, the Canary Islands, and the Azores, where part of the German merchant marine had sought refuge, and were suspected of supporting German U-boats. Unlike the German submarine force, French officers were ordered to respect the terms of the London Naval Treaty: the submarines had to announce their presence to merchant ships prior to an attack, and could only fire on the ship when the crew had evacuated it. These precautionary measures reduced the effectiveness of the French submarine force. Redoutable encountered a merchant vessel sailing without lights during the night of 1 November. The vessel refused to comply with a request from the submarine to stop, so the submarine fired warning shots with her 100 mm deck gun. The merchant vessel returned fire. Redoutable then received a message from the British cargo ship Egba, which was reporting that she was under attack by a "U-boat". Realising that the merchant ship she was firing on was a British one, Redoutable ceased the attack.
In December 1939, , , Redoutable, and Le Héros were sent into the Atlantic to search for the German tanker , which had been supplying the German cruiser . Altmark, carrying prisoners taken from ships attacked by the German cruiser, evaded detection and sailed towards Norway, where it was eventually captured by British ships in the Altmark incident. During the winter of 1939–1940, Achille, Casabianca, Pasteur, and escorted three Allied convoys from Halifax, Nova Scotia to the United Kingdom. They were relieved in February by and Sidi-Ferruch, and then, in April, by Archimède and Ajax.
Italy declared war on France on 10 June 1940. Fresnel, Le Tonnant, Redoutable, and Vengeur patrolled along the Tunisian coast to prevent an Italian landing, while Centaure and Pascal conducted surveillance operations south of Sardinia. Archimède participated in Operation Vado. With the German advance in June, the port of Cherbourg and the arsenal of Brest were evacuated, ships principally heading towards Casablanca and Dakar. On 18 June Agosta, Achille, Ouessant and Pasteur were scuttled in the port of Brest, having been prevented from putting to sea.
By the time the armistice was signed on 22 June 1940, not one of the 29 Redoutable class had sunk any German or Italian ships. Only Poncelet had had any success, her crew having boarded the merchant vessel Chemnitz and sailed her to Casablanca. The cause of this lack of success was the utilization of the submarines as escorteurs and squadron eclaireurs, instead of as chasseurs, in strict adherence to the terms of the Treaty of London, coupled with problems associated with the age and obsolescence of the vessels.
Vichy service
The conditions of the armistice envisaged the return of French naval vessels to their home ports to be disarmed; however, the British attack on Mers-el-Kébir on 3 July convinced the Germans to cancel this plan. The French lost two Redoutable-class submarines during the Battle of Dakar on 23 and 24 September; on 23 September Persée was sunk by two British destroyers after having tried to torpedo unsuccessfully; on 24 September Ajax was fired upon by several destroyers escorting the British squadron and was consequently scuttled after the crew abandoned ship. In both cases, the crews were rescued by the British. On 25 September Bévéziers, under the command of Capitaine de corvette Lancelot, attacked and damaged the battleship , which was out of service for almost nine months.
On 28 October the French naval forces were re-constituted under Vichy government control, under the direction of the German and Italian armistice commissions. Only the Second Submarine Division, consisting of Casabianca, Sfax, Bévéziers and Sidi-Ferruch, based in Casablanca, and the four submarines sent to Madagascar, Vengeur, , Monge and remained armed. The remainder of the Redoutable class were to be placed under guard at Toulon. Those submarines on active service were relieved one after the other in pairs by units from Toulon, in order to conduct necessary repairs and refits. Defective parts were replaced; however the terms of the armistice prevented upgrades to extend their fighting capabilities.