Jean Bart et son jumeau Richelieu sont les unités les plus lourdes, les plus puissantes et les mieux armées construites par la marine nationale à l'aube de la Seconde Guerre mondiale. Ces deux cuirassés sont l'amélioration de leurs aînés, les croiseurs de bataille Dunkerque et Strasbourg, mais plus lourds, plus rapides, plus puisamment armés et, surtout, mieux protégés. Pour les caractéristiques techniques, voir Alabordache.
Derived from the Dunkerque class, Jean Bart (and her sister ship Richelieu) were designed to counter the threat of the heavy ships of the Italian Navy. Their speed, shielding, armament, and overall technology were state-of-the-art, but they had a rather unusual main battery armament arrangement with two 4-gun turrets to the bow and none to the stern. Jean Bart was laid down in December 1936, and she was launched on 6 March 1940. Barely 75% completed, her steam engines never having been worked before, she was taken of St. Nazaire's dry dock by Captain Ronach and steamed to Casablanca, Morocco, in June 1940 in order to escape the advance of the German army in France. Only one of her two 380 millimetres (15 in) main turrets had been installed by then. The second turret, with only two of its four naval guns, was loaded onto a cargo ship. This ship was torpedoed and sunk by a German U-Boat. Her 152 millimetres (6.0 in) secondary battery was also non-installed, and it was replaced by anti-aircraft guns. Like other French naval and military forces in North Africa, the Jean Bart was under the control of the Vichy French government. On 8 November 1942, during Operation Torch, the French fleet in Casablanca was attacked by American warships and warplanes from the aircraft carrier USS Ranger (CV-4). The Jean Bart went into a gunbattle with the battleship USS Massachusetts (BB-59). The Jean Bart suffered hits from several aerial bombs and 16 inch (406 mm) shells. On the 10th, the Jean Bart opened fire again onto the cruiser USS Augusta, much to the surprise of the American naval officers - who thought that the Jean Bart had been silenced by her heavy damage. This gunfire drew action from the warplanes of the USS Ranger, and the Jean Bart suffered two more hits by 500 lb bombs. These opened a leak in her hull, forcing her to be run aground by her Captain. Combat was over by that evening, and along with the rest of French forces in North Africa, she surrendered and then took sides with the Allies of the United States and the United Kingdom.
Soon, it was suggested that the Jean Bart be towed to the USA and completed there (her sistership, Richelieu, had already undergone a refitting there), but that proved to be impossible. The notion of converting the Jean Bart into an aircraft carrier were studied, but they were found to be impractical. For the next two years, the unfinished battleship remained stranded in Casablanca harbor. The Jean Bart returned to France in 1945, and she was completed in 1949, under an updated design influenced by lessons from experience with battleships in the previous war. The Jean Bart took her part in the Suez Canal Crisis off Egypt in 1956, but engaged in no ship-to-ship combat. She was put into reserve in 1957, and then she was decommissioned in 1961. The hulk of the Jean Bart was scrapped in 1969.