In the years before the outbreak of World War I in 1914, the French Navy considered several proposals for battlecruisers. The Navy issued specifications for a battlecruiser design to complete part of the 28 capital ships to be built by 1920. Three designs, one by P. Gille and two by Lieutenant Durand-Viel, were completed in 1913. All three designs were similar to contemporary battleship designs, specifically the Normandie class, which introduced a quadruple gun turret for the main battery, which was adopted for all three proposals. The first two called for the same 340 mm (13.4 in) gun used on all French super-dreadnoughts, though the third proposed a much more powerful 370 mm (14.6 in) gun. Though the design studies were complete, the French Navy did not authorize or begin construction of any battlecruisers before the start of the war.

In the Naval Law of 30 March 1912, the French Navy called for a total force of 20 capital ships to be built by 1920. The Technical Branch subsequently issued a set of somewhat vague requirements for battlecruiser designs. The requirements stipulated a displacement of 28,000 metric tons (28,000 long tons; 31,000 short tons), a speed of 27 knots (50 km/h; 31 mph), an armament of eight 340 mm (13.4 in) guns, and a crew of not more than 1,200 officers and enlisted men. These figures were very similar to the British Lion-class battlecruisers then under construction. Numerous proposals were submitted to the Technical Branch, but only two were evaluated further. The first was prepared by P. Gille, a naval engineer overseeing the construction of the Normandie-class battleship Flandre, and the second by then-Lieutenant Durand-Viel, a student at the Naval College. As the proposals were only design studies, none were authorized and no ships were built; the outbreak of World War I ensured that even more advanced projects, like the Normandie and Lyon-class battleships were canceled as resources were redirected toward more pressing needs.^[1][2][3]

In 1911, Gille went to Britain to observe the construction of the new Orion-class battleships and the Lion-class battlecruisers. The latter ships prompted Gille to decide the French Navy ought to build battlecruisers as well, since Britain and Germany had already begun acquiring them, and they would prove useful as a fast division of the French fleet. Gille decided that his proposed ship would need a top speed of 28 to 29 kn (52 to 54 km/h; 32 to 33 mph) to retain an advantage over foreign battleships, the latest of which had estimated speeds of 22 to 23 kn (41 to 43 km/h; 25 to 26 mph). They would also need enough armor and a main battery powerful enough to fight in the line of battle. The limitations that weight imposed on the design, however, restricted the amount of armor possible, and so the traditional French practice of armoring the entire side of the ship would be impossible.^[4]

Gille's battlecruiser design called for a displacement of 28,247 t (27,801 long tons; 31,137 short tons) on a hull that was 205 meters (673 ft) long between perpendiculars, with a beam of 27 m (88 ft 7 in) at the waterline and an average draft of 9.03 m (29 ft 8 in). The freeboard forward was 7.15 m (23 ft 5 in), and aft was 4.65 m (15.3 ft). The hull lines of the ships proved to be highly efficient in tank tests during the design process. Due to the extreme weight of the main battery turrets at the bow and stern, the hull had to be strengthened to handle the strain. Very strong longitudinal bracing was incorporated, and the inner and outer skins of the hull was thickened to reinforce the bracings. The ships' expected metacentric height was 1.03 m (3 ft 5 in), comparable to the British Lion class. Each ship would be crewed by 41 officers and 1,258 enlisted men.^[5]

The ships would have been equipped with four sets of steam turbines rated at 80,000 shaft horsepower (60,000 kW) powered by fifty-two coal-fired Belleville boilers. Each propeller shaft was connected to a high-pressure turbine, a medium-pressure geared turbine, and a low-pressure turbine for forward steaming, and a direct drive turbine for steaming in reverse. The ships' top speed was to have been 28 knots. The ships would have been supplied with 2,833 t (2,788 long tons; 3,123 short tons) of coal and 630 t (620 long tons; 690 short tons) of fuel oil for supplementary oil firing. At maximum speed, the ships could have cruised for 1,660 nautical miles (3,070 km; 1,910 mi); at 20.3 kn (37.6 km/h; 23.4 mph), the range increased to 4,240 nmi (7,850 km; 4,880 mi), an at a more economical 15 kn (28 km/h; 17 mph), the range grew to 6,300 nmi (11,700 km; 7,200 mi).^[1][5]

The ships' main armament was composed of twelve 340mm/45 Modèle 1912 guns in three quadruple turrets, the same as in the contemporary French battleships of the Normandie class. One turret was placed forward, and the other two were placed in a superfiring pair, all on the centerline.^[1][5] The guns had a range of 16,000 m (17,000 yd) and had a rate of fire of two rounds per minute. The shells were 540-kilogram (1,190 lb) armor-piercing rounds and were fired with a muzzle velocity of 800 meters per second (2,600 ft/s).^[6] A secondary battery of twenty-four 138.6 mm /55 Modèle 1910 guns mounted in casemates was planned for defense against torpedo boats.^[1][5] These guns fired a 36.5 kg (80 lb) shell at a muzzle velocity of 830 m/s (2,700 ft/s).^[7] The armament was rounded out by six torpedo tubes of undetermined diameter, all submerged in the ships' hulls.^[1][5]

The armor protecting both the main armored belt amidships and the main battery turrets was 270 mm (10.6 in) thick. The lower armored deck was 20 mm (0.79 in) thick, with 50 mm (2.0 in) of armor plating on the sloped sides. The casemate guns were protected with 180 mm (7.1 in) of steel armor. The ships were also equipped with a 20 mm thick torpedo bulkhead.^[1][5]

In 1913, the Naval College had several of its students submit design studies for a fast capital ship. The class was given a displacement of 27,500 t (27,100 long tons; 30,300 short tons) as a limit on size; all of the officers opted to design either fast or slow battleships, with the exception of Lieutenant Durand-Viel, who chose instead to create a design for a battlecruiser. Durand-Viel drew up a pair of designs, which were evaluated by the General Staff in June 1914. He saw his ships forming a fast division of the battle fleet capable of encircling an enemy squadron; as with Gille's design, this required heavy armament and armor to permit the ships to engage battleships.^[8]

Durand-Viel's first battlecruiser design, "A", was built on a displacement of 27,500 t (27,100 long tons; 30,300 short tons). The hull was 210 meters (690 ft) long at the waterline, with a beam of 27 m (89 ft) at the waterline and an average draft of 8.7 m (29 ft). The ships would have been equipped with four sets of direct drive turbines rated at 74,000 shaft horsepower (55,000 kW) powered by twenty-four double-ended Belleville boilers that burned both coal and oil. The ships' top speed was to have been 27 knots (50 km/h; 31 mph). The ships would have been supplied with 1,810 t (1,780 long tons; 2,000 short tons) of coal and 1,050 t (1,030 long tons; 1,160 short tons) of fuel oil . The ships could have cruised for 3,500 nautical miles (6,500 km; 4,000 mi) at 16 kn (30 km/h; 18 mph), with enough fuel for an additional six hours for combat speeds.^[1][9]

The ships' main armament was composed of eight 340mm/45 Modèle 1912 guns in two quadruple turrets, the same as in the contemporary French battleships of the Normandie class. Both turrets were placed on the centerline, on either end of the ship. A secondary battery of twenty-four 138.6 mm Modèle 1910 guns mounted in casemates was planned for defense against torpedo boats. Four 47 mm (1.9 in) saluting guns were also to be equipped. The armament was rounded out by four 450 mm (18 in) torpedo tubes, all submerged in the ships' hulls. The main armored belt amidships was 280 mm (11 in) thick, slightly thinner than the belt on the Normandie-class battleships. The rest of the ship's armor was very similar to that of the Normandie class.^[1][10]

Durand-Viel's second battlecruiser design, "B", was built on the same displacement as the first design. The heavier weight of the increased main battery was offset by a reduction in the armor protection for the secondary guns and improved performance of the ship's propulsion system. The hull was 208 meters (682 ft) long at the waterline, with a beam of 27 m at the waterline and an average draft of 8.7 m. Two engine systems were considered: four direct drive turbines rated at 63,000 shp (47,000 kW) or four geared turbines rated at 80,000 shp (60,000 kW). Steam was provided by eighteen Belleville boilers, ten of which that burned both coal and oil, and eight that were oil-fired only. The ships' top speed was to have been 26 knots (48 km/h; 30 mph) for the first variant and 27 knots for the second. The ships would have been supplied with the same fuel allotment as the "A" design, with the same radius of action as well.^[1][11]

The ships' main armament was composed of eight 370 mm (15 in) guns in two quadruple turrets. Both turrets were placed on the centerline, on either end of the ship. The gun fired a 880-kilogram (1,940 lb) shell that was capable of penetrating 300 mm (12 in) of armor plate at a range of 12,700 m (41,700 ft). A secondary battery for defense against torpedo boats consisted of twenty-eight 138.6 mm guns, of a new semi-automatic design, mounted in casemates. Four 47 mm saluting guns were also to be installed. The should would also to have carried four 450 mm torpedo tubes, all submerged in the ships' hulls. The ships' armor system was identical to the "A" design.^[1][11]

• Friedman, Norman (2011). Naval Weapons of World War One. Annapolis: Naval Institute Press. ISBN 978-1-84832-100-7.
• Gardiner, Robert & Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships 1906–1921. Annapolis: Naval Institute Press. ISBN 978-0-87021-907-8.
• Jordan, John & Caresse, Philippe (2017). French Battleships of World War One. Barnsley: Seaforth Publishing. ISBN 978-1-59114-639-1.
• Le Masson, Henri (1985). "Some French Fast Battleships That Might Have Been". Warship International. XXII. International Naval Research Organization: 149–156.