Lagrange-class submarine

The Lagrange-class submarines were a class of four submarines built for the French Navy during World War I and the interwar period. Three ships of this type were built in the Arsenal de Toulon from 1913 to 1924, and one was built the Arsenal de Rochefort shipyard. The submarines entered the Marine Nationale from 1918 to 1924 and served until the mid-1930s.

Design
The Lagrange class was constructed as part of the French fleet's expansion programmes from 1913 to 1914. The ships were designed by Julien Hutter, slightly modifying his previous project Dupuy de Lôme, using two Parsons steam turbines with a power of 2000 hp. During construction, though, the idea was abandoned and the ships were instead equipped with diesel engines.

75.2 m long, with a beam of 6.3 m and a draught of 3.6 m, Lagrange-class submarines could dive up to 50 m. The submarine had a surfaced displacement of 920 t and a submerged displacement of 1318 t. Propulsion while surfaced was provided by two 2600 hp diesel motors built by the Swiss manufacturer Sulzer and two 1640 hp electric motors. The submarines' electrical propulsion allowed it to attain speeds of 11 kn while submerged and 16.5 kn on the surface. Their surfaced range was 7700 nmi at 9 kn, and 4000 nmi at 12 kn, with a submerged range of 70 nmi at 5 kn.

The ships were equipped with eight 450 mm torpedo tubes (four in the bow, two stern and two external), with a total of 10 torpedoes and two on-board guns. The class was also armed with a 75 mm with an ammo supply of 440 bullets. The crew of one ship consisted of four officers and 43 of officers and seamen.

Ships
Of the four Lagrange class submarines, three ships were built in the Toulon Arsenal, and one in the Arsenal de Rochefort. The member ships were laid down between 1913 and 1914, and launched between 1917 and 1924. The ships were named after distinguished French scholars: Joseph-Louis Lagrange, Pierre-Simon Laplace, Henri Victor Regnault, and the constructor of submarines Gaston Romazzotti.

Service
Of the four submarines, only two were commissioned before the end of World War I: Lagrange and Romazzotti, which operated in the Mediterranean Sea.

From 1922 to 1923, the ships underwent a major refit in which they received new major kiosks, bridges and periscopes. All ships served in the Mediterranean Sea until 1935 for Lagrange and 1937 for the other three ships.