Suffren-class cruiser
In 1925 there was a provision for a treaty cruiser of 10,000 tons based on the Tourville design. The General Staff changed a requirement focusing more on protection than speed. Machinery was reduced to three shafts with the corresponding weight savings put towards increasing the armour of the vessel. The change to a three shaft arrangement lowered the corresponding horsepower lever the 90,000 CV (chevaux - horses).* The initial vessel would retain the same armament as the preceding . The hull and internal layout would also be very similar. The vessel would be the first vessel of the . Four  vessels would be built over the next five years with incremental changes in each. Initially classed as a croiseur Leger (Light Cruiser) all ships were reclassified on 1 July 1931 as a croiseur de 1ere classe (First class cruiser). The Marine Nationale did not have a vessel classification of heavy cruiser instead used croiseur cuirasse (armoured cruiser) and croiseurs legers (light cruiser) prior to the London Naval Treaty then croiseur de 1ere classe (First class cruiser) and croiseur de 2e classe (Second class cruiser) afterwards. Design and description. Hull and Protection. The design of the "Suffren" class was based on  the light cruiser while maintaining the standard displacement of 10.000 tons. The hull maintained the high freeboard with the raised forecastle of all post-war cruisers with excellent sea keeping qualities. The hull design also kept the fine lines for the speed requirement complemented by the clipper bow with a gentle sheer and the marked flare keeping the forecastle dry even in heavy weather. The framing in a French hull was numbered from aft to stem, frame numbering was based on the distance from the aft perpendicular in meters. The longitudinal framing was used for cruisers throughout the interwar period . The hull was between the perpendiculars with an overall length of and a beam of . At her normal displacement of 11,769 tonnes the draft of the ship would be . The protection was increased over the previous . The armour protection in the hull for the was only 370 tons whereas Suffern would have 670 tons. The upper deck was thick amidships with bulkheads running to within of the sides enclosing the funnel uptakes and ventilation trunking between the main and first deck. The magazines were enclosed in an armoured box with sides and crowns, forward and aft bulkheads. The turrets and  conning tower had plating. The roofs of both the turrets and range finders was of cast nickel. The steering gear was housed inside an armoured box with sides and an top. A Belt of made of non-cemented 60 kg steel was installed to a height of and below the waterline abeam of the machinery spaces in "Suffren" and "Colbert" only. The space between the machinery bulkhead and the inside of the hull was approximately . For "Suffren" and "Colbert" this space was filled with 500 tons of coal for the cruising boilers and therefore did not count against the standard  displacement. Reinterpreting the rules of the Washington Naval Treaty, the STNC decided to change and improve the level of protection on the next cruiser of the series, "Foch". The interpretation was for Washington standard displacement to mean a peacetime load versus what would be required for a full wartime load. With the concept of shells striking the sides above the shallow armoured belt being able to penetrate to the machinery spaces, it was decided to do away with the belt and replace it with an armoured box around the machinery. The sides of this armoured box was with the deck  above of the armoured box was . The bulkheads of the box varied in height from to . The protection on the sides of the magazines was increased to with all other protection remaining the same. The last cruiser of the program, "Dupleix" would be protected along the same lines as "Foch".but with a slight increase. All longitudinal bulkheads were increased from to on the magazines and machinery spaces. The main deck over the machinery spaces was increased from 18 mm to . The upper deck however, was decreased from to . The magazine crowns were also increased to . Machinery. The propulsion system was  changed from the four shaft arrangement of the to a three shaft arrangement in the . Three single reduction gear Rateau-Bretagne steam turbines with six Guyot du Temple small tube boilers built by Indret rated at 20 kg/cm2 while operating at 215° Fahrenheit would produce 90,000 CV (chevaux - horses)* on three shafts to achieve a designed speed of 32 knots. The forward boiler and engine rooms would be the same as in the . The forward engine room would drive the wing shafts. The aft boiler rooms and turbine would be inline driving the center shaft. Each boiler room  would have only one boiler. Between the forward engine room and the aft boiler rooms two smaller coal/oil fired boilers would be installed in "Suffren" and "Colbert" only. These smaller boilers would be connected to the center line turbine for low speed cruising and were known as cruising boilers. The six main boilers would be oil fired with a maximum load of 1,876 tons of oil giving an endurance of 4,600 nm at 15 knots and 3,700 nm at 20 knots. For "Suffren" and "Colbert" carried 640 tons of coal for the cruise boilers and would provide another 2,000  nm at 11 knots. Twin side by side rudders were installed abaft between the shafts. To reduce the tactical radius of the vessels the centerline skeg was removed in the first three vessels ("Suffren", "Colbert" and "Foch") though it was reinstalled on the fourth unit ("Dupleix"). They were considered good sea boats and responsive to the helm at speeds above 10 knots. Armament. The requirement for main the armament of eight guns housed in four lightly armoured turrets with 120 rounds per gun and with maximum magazine storage of 150 rounds per gun during wartime. The weapon used was the  203 mm/50 (8 in) Model 1924 naval gun. The guns were mounted in four Cruiser Two Gun Turret Model 1924 providing a separation of the axis of the guns by 74 inches. The turret was plated with two sheets of 15 mm high tensile steel plate riveted together placed on all sides and roof for armour protection of 30mm. The mount provided an elevation from minus 5 degree to plus 45 degrees with an elevation rate of ten degrees per second. The mount could be trained to plus or minus 90 degrees from the centerline of the vessel with  a train rate of six degrees per second. The guns could be loaded at any degree of train but only between minus 5 and plus ten degrees in elevation. The loading cycle started with the rammer cocked by the recoil of the guns. A dredger hoist brought the shell and two half charge bags to the breech. The rammer drove the shell into the breech with the powder being loaded by hand. The breech would close and the gun would be fired. The guns could maintain a rate of fire of four to five rounds per minute. For the secondary  armament, "Suffren" was to maintain the eight 75 mm/50 (2.95 inch) model 1924 naval gun on single Model 1922 gun mounts placed in the same positions as the . Starting with the "Colbert" it was decided to upgrade these weapons with the 90 mm/50 (3.5 inch) Model 1925 gun on Model 1926 single mounts. The 90 mm guns replaced the 75 mm on "Foch" and "Dupleix" as well and would be mounted in the same positions as the 75 mm guns. For "Dupleix" the mount was changed to the Model 1930 dual mount thereby reducing the number of mounts from eight  to four. The medium anti-aircraft armament was augmented with 37 mm/50 (1.46 inch) model 1925 guns in Model 1925 single mounts. "Suffren" would carry eight whereas the remaining three would only have six. With an elevation only to plus 85 degrees they had a slow rate of fire, 15 to 21 rounds per minute therefore were not effective against modern aircraft when installed. Starting in 1943, these guns would be replaced with single 40 mm Bofors on "Suffren" only as the equipment became available. To complete the light AA armament it was intended to install four single 8 mm  Hotchkiss machineguns on the quarterdeck just aft of the last 203 mm turret as in the Duquesne. However, it was recognized that these weapons were ineffective against aircraft of the period so they were replace by twelve 13.2 mm (0.5 inch) Model 1929 machineguns. Two would be mounted forward on the lower bridge wings and the other four in place of the 8mm machineguns. These guns would be mounted in twin mountings. For "Colbert", "Foch" and "Dupleix" it was intended that the forward machine guns would be quad mounts. The mounting was unavailable and only ‘’Courbert’’ had them installed  in 1941. In 1943 they were replaced on "Suffren" only by 20 mm Oerlikon cannons based on the availability of the equipment. For torpedoes two launchers Model 1925T for 550 mm torpedoes were fitted to port and starboard. When in the locked position the starboard launcher faced forward and the port launcher faced aft. The tubes could be trained and fired either locally or from the armoured conning tower. The ships initially carried the was the 55 cm (21.65 inch) 23DT, Toulon torpedo. Nine torpedoes were carried, six in the tubes with three spares. The torpedo tubes were landed  on "Suffren" only between 1943 and 1945. Aircraft. Two catapults would be installed on these vessels. Two Gordou-Lesseurre GL-810 float planes would be shipped. On "Suffren" the catapults were installed between the aft funnel and the main mast. For the remaining three the catapults would be moved forward to be between the funnels. Two aircraft would be carried until 1937 when the catapults were removed for modification. Once the modification was complete the catapult was reinstalled with a Loire 130 float plane. "Suffren" would land her catapults and aircraft between 1943 and 1945. History. "Suffren" was first to enter  service in 1929 joining the First Light Squadron at Toulon. "Colbert", "Foch" and "Dupleix" would also join the First Light Division at Toulon upon completion. In 1934 "Suffren" along with the two Duquense class cruisers would be reassigned to the Third Light Division. All would remain there in Toulon until 1939. In June 1939 Suffren departed for French Indochina to relieve the cruiser "Primauguet". With the outbreak of war in September "Suffren" patrolled the South China seas on the lookout for German merchantmen. In November she went to Singapore to aid in the escort of an Australian troop convoy to  Colombo. She continued to escort convoys in the Indian Ocean until the end of April 1940. In May she returned to the Mediterranean to be assigned to Force X at Alexandria. Here she made two sorties against the Italians but no targets were found. With the French armistice in June 1940 she was demilitarized along with the other units of Force X. "Colbert", "Foch" and "Dupleix" joined Force X at Dakar in late 1939 and patrolled the mid-Atlantic searching for the "Graf Spee" and German merchant vessels. The three returned to Toulon in January 1940. In June 1940 they  along with "Algerie" bombarded Genoa and Vado. At the time of the Armistice were based at Toulon. All three were scuttled there in November 1942. "Suffren" returned to the Allied cause in May 1943, sailed for Dakar for blockade patrol in the Atlantic. Underwent a major refit in 1945. Her last operations were during the restoration of French control over French Indochina. Placed in reserve in 1947 and used as a training hulk. In 1962 she was renamed "Ocean" then stricken in 1972.