"Bretagne" was laid down on 4 August 1851 and "Desaix" on 27 Octobre. On 17 June 1852, the Ministry of the Navy suspended construction and required that the ships be lengthened by 3.43 metres and that 540 shp steam engines be incorporated. Brest responded to the requirements in September 1852, but at the same point, Dupuy de Lôme's fast ship of the line "Napoléon" was completing her trials, exhibiting such outstanding performances that on 10 September 1852 the Ministry cancelled the "Bretagne" class and ordered existing sailing ships to be converted to steamers, using as many existing parts as possible. At this point, the keel, bow and aft of "Bretagne" had been erected, amounting to the third of the 24 construction steps defined by regulations in ship construction; she was taken apart and rebuilt according to Marielle's plans, which had been approved in December 1852. At the same time, the order for the steam engine was placed. "Desaix", whose keel was only beginning to be laid, was cancelled altogether and "Arcole", second ship of the "Algésiras" type, the production series of the "Napoléon" design, was started instead.