To keep the ships within the displacement limits imposed by the Washington Naval Treaty, they featured the same concentrated arrangement as the Dunkerques for the main battery: two quadruple gun turrets placed forward.

Richelieu was finished shortly before the French defeat in the Battle of France, while Jean Bart was hurriedly prepared to be ready to go to sea during the campaign.

After the war, Richelieu took part in the initial campaign to restore control of French Indochina before returning to France, where she saw limited activity into the early 1950s.

The Italian Regia Marina (Royal Navy)—France's other major naval rival—announced on 11 June 1935 that it would begin building two 35,000-long-ton (36,000 t) battleships of the Littorio class in response to the Dunkerques.

At the time, battleship construction was governed by the Washington Naval Treaty, which limited displacement to 35,000 tons and gun armament to 406 mm (16 in).

[1] The French naval command issued specifications for a new battleship design in response to the Littorios on 24 July, less than two weeks after the Italian ships were announced.

[2] Initial studies by the design staff quickly demonstrated that a battery of 406 mm guns would be impossible if the other characteristics would be fulfilled within the allotted displacement.

Two related variants, Project 5 and 5 bis adopted an even more unusual arrangement featuring two quadruple turrets placed amidships between fore and aft superstructures inspired by the ideas of the Italian admiral Vincenzo De Feo.

[3] The naval command quickly settled on Project 1, as it had the most balanced combination of speed and combat power—offensively and defensively—that could realistically be achieved within the displacement constraints imposed by the Washington Treaty (and the existing French shipyard facilities).

[7][9] The Richelieu-class ships were powered by four Parsons geared steam turbines and six oil-fired Sural forced-circulation boilers manufactured by Indret for Richelieu and by Penhoët and AC de la Loire for Jean Bart.

The Sural boilers were experimental, and were thus a major risk to take with what were to be the most powerful capital ships of the French fleet; they nevertheless proved to be generally reliable in service.

The directors gathered range and bearing data on targets and transmitted it to a central processing station that fed instructions to the gun crews.

The void between the armor belt and the outer hull plating was filled with a rubber-based compound referred to as ébonite mousse; the material was used to absorb the impact of an explosion and prevent water from flooding uncontrollably.

This bulkhead was increased to 40 to 50 mm (1.6 to 2.0 in) abreast of the secondary magazines and the forward main battery turret, as the narrowing hull reduced the total width of the underwater protection system.

[20] The command wanted to compare their new ships with the latest foreign contemporaries; they noted that all other battleships carried their main armament forward and aft, and several of them used dedicated high and low-angle guns for their secondary batteries.

The 130 mm dual-purpose guns used on the Dunkerques were proving to be troublesome in service, and the command wanted to determine whether the arrangement would be suitable for future construction.

Both variants necessitated significant changes to the arrangement of other equipment, including the light anti-aircraft batteries and aviation facilities, but Gascogne required much more radical work.

These guns proved to be problematic during development, owing to excessive barrel wear that resulted from its very high muzzle velocity and the weight of the projectile.

Efforts to correct the problem had delayed the adoption of this gun for the earlier Richelieus and it never actually entered service apart from a prototype installed on the aviso Amiens.

[26] Another major effect of the main battery rearrangement was the need to lengthen the belt armor, which necessitated alterations to keep displacement in check.

[27] Work on Richelieu was expedited as war with Germany became increasingly likely in 1939, and she was completed just days before the Germans won the Battle of France in June 1940.

These included escorting British and American aircraft carriers as they struck Japanese facilities in the occupied Dutch East Indies and several bombardment operations that revealed problems with excessive shell dispersion from her main battery guns.

Testing determined the cause of the shell dispersion issue and modifications were made to the turrets to delay the outer guns by 60 milliseconds, which corrected the problem.

[42][43][44] Jean Bart had only recently been launched by the beginning of the Battle of France in May 1940, so the shipyard focused as much effort on getting the ship ready for sea as possible.

With German forces approaching Saint-Nazaire, Jean Bart was rushed through a hastily-dredged channel to escape via the Atlantic Ocean south to Casablanca.

After being attacked and hit once (but not seriously damaged) by German Heinkel He 111 bombers while en route, the ship reached Casablanca with an escort of two destroyers on 22 June.

The facilities there were not capable of completing the second main battery turret, nor were the Germans interested in allowing the needed armor plates and guns to be shipped there.

They submitted proposals to complete the vessel to modified designs, including one with as many as thirty-four 5 in (130 mm) /38 caliber dual-purpose guns for use as an anti-aircraft battleship, but the requests came to nothing as the US Navy had no interest in the project.

Since the carrier conversion would have produced a mediocre vessel at great expense and effort, the decision was ultimately made to finish her as a battleship, a process that took several years.

Most work on the ship was completed by 1955, when she formally entered active service, and she conducted two overseas cruises to visit Denmark and the United States shortly thereafter.