[1][2] The design for the new ships was prepared in early 1875 by Louis de Bussy, who had also designed Redoutable; he originally intended to arm the new ship with four 320 mm (12.6 in) guns and two 274.4 mm (10.80 in) guns, the former in a central casemate and the latter in open barbettes above the casemate.

[3] The Conseil des travaux (Board of Construction) examined his initial proposal on 16 March 1875, and made several requests for changes.

These included changes to the arrangement of some of the guns, an extension of the armor deck for the entire length of the ship, and the addition of a second propeller.

As was standard for French capital ships of the period, they had a pronounced ram bow and tumblehome sides.

The ships carried 565 long tons (574 t) of coal, which provided a cruising radius of 3,100 nautical miles (5,700 km; 3,600 mi) at an economical speed of 10 knots (19 km/h; 12 mph).

[4][6] The ships' main battery consisted of four 340 mm guns mounted in a central, armored casemate.

These were supported by a secondary battery four 274.4 mm guns; Dévastation's were 18-caliber M1870 weapons and Courbet's were slightly longer 19.75-caliber M1875 pieces.

For defense against torpedo boats, Dévastation carried eight 37 mm (1.5 in) 1-pounder Hotchkiss revolver cannon, all in individual mounts, while Courbet was completed with eighteen of the guns.

At the same time, her propulsion system was replaced with new vertical triple-expansion steam engines and twelve Belleville boilers of the water-tube type.

More extensive work was carried out in 1897, when the ship received a new, larger conning tower with 80 mm of armor plate.

The light guns that had been present in her upper fighting tops were removed, as were the two forward torpedo tubes.

The Navy had intended to completely rearm the ship, but a change in naval ministers led to a shift in priorities, so the alterations to the main and secondary batteries were deferred.