The Charles Martel class was a planned class of ironclad barbette ships of the French Navy. The class comprised two ships, Charles Martel and Brennus, and represented an incremental improvement over the preceding , being larger, but carrying the same main battery of four guns in single mounts. Details of the ships' construction are unclear and contradictory, with various sources reporting that both ships were laid down, or that only Brennus was begun; neither ship was launched before they were cancelled in 1884 or 1886. Some sources indicate that Brennus was redesigned and completed as France's first pre-dreadnought battleship, , but most other historians dispute the idea.
Background
After the Franco-Prussian War of 1870–1871, the French Navy embarked on a construction program to strengthen the fleet in 1872 and to replace older vessels that had been built in the 1860s. By the early 1870s, the Italian (Royal Navy) had begun its own expansion program under the direction of Benedetto Brin, which included the construction of several very large ironclad warships of the and es, armed with 100-ton guns. The French initially viewed the ships as not worthy of concern, but by 1877, public pressure over the new Italian vessels prompted the Navy's (Board of Construction) to respond, beginning with the barbette ship and following with six vessels carrying 100-ton guns of French design. The first of these were the two s, which carried their guns in open barbettes, all on the centerline, with one forward and two aft.
By the early 1880s, the very large guns had fallen out of favor in the French Navy, so the remaining four ships, to be laid down beginning in 1880, were redesigned with smaller but equally powerful weapons. These became the , which was to have comprised four ships but ultimately included only three. The first vessel that was laid down, , had to be reworked after it was realized that the ship was too small for the intended displacement. The remaining three ships, which had not yet been laid down, could be enlarged to the necessary dimensions. All four ships arranged their main battery in a lozenge pattern with one forward, one aft, and a wing mount on either side amidships to maximize end-on fire (which was emphasized by those who favored ramming attacks).
At the same time, developments with quick-firing guns rendered the generation of French capital ships designed in the 1870s and early 1880s dangerously vulnerable to damage above the waterline. These ships used shallow waterline belt armor to protect their sides, but most of their hulls were unprotected by armor altogether. Many navies began to incorporate thin side protection above the belt to deal with the threat. Further complicating matters were the developments of self-propelled torpedoes and small, fast torpedo boats that posed an existential threat to the battleship-dominated fleets of the European navies.
Development and cancellation
The fleet program of 1880 projected a total of six new ironclad battleships; the first four were to be the three Marceaus and Hoche. The remaining pair of vessels was due to begin construction in 1882. An initial plan by the naval engineer Louis de Bussy proposed a ship modeled on the British ironclad , carrying a main battery of four guns in a pair of gun turrets arranged en echelon amidships. Before work on the vessels began, the French naval command reconsidered and opted for an improved Marceau, and a new design was prepared by Charles Ernest Huin, who had designed the Marceaus and Hoche. The new design repeated the lozenge arrangement of the main battery in single mounts.
The exact timeline for the design and construction of the ships are unclear. According to the historians John Jordan and Philip Caresse, Huin's design was approved in January 1885 and work on the two ships, Charles Martel and Brennus, began that year in Toulon and Lorient, respectively. They credit Admiral Théophile Aube, who became the French Minister of Marine in January 1886, as immediately suspending work on the new ships upon becoming the naval minister. Aube was a proponent of the (Young School), which held that cheap torpedo boats could effectively replace the capital ships that had been the primary component of naval power.