Compared to iron, steel allowed for greater structural strength for a lower weight. France was the first country to manufacture steel in large quantities, using the Siemens process. At that time, steel plates still had some defects, and the outer bottom plating of the ship was made of wrought iron.
Redoutable formed part of the French Mediterranean squadron.
The Redoutable is built partly of iron and partly of steel and is similar in many respects to the ironclads Devastation and Courbet of the same fleet, although rather smaller. She is completely belted with 14 in (360 mm) armour, with a 15 in (380 mm) backing, and has the central battery armoured with plates of 9½ in (240 mm) in thickness.
The engines are two in number, horizontal, and of the compound two cylinder type, developing a power of 6,071 horsepower (4.465 kW), which on the trial trip gave a speed of 14.66 knots. Five hundred and ten tons of coal are carried in the bunkers, which at a speed of 10 knots should enable the ship to make a voyage of 2,800 nautical miles (5,200 km). Torpedo defense netting is fitted, and there are three masts with military tops carrying Hotchkiss revolver machine guns.
The offensive power of the ship consists of seven breechloading rifled guns of 27 centimeters (10.63 in.), and weighing 24 tons each, six breechloading rifled guns of 14 centimeters (5.51 in.), and quick-firing and machine guns of the Hotchkiss systems. There are in addition four torpedo discharge tubes, two on each side of the ship.
The positions of the guns are as follows: Four of 27 centimeters in the central battery, two on each broadside; three 27 centimeter guns on the upper deck in barbettes, one on each side amidships, and one aft. The 14 centimeter guns are in various positions on the broadsides, and the machine guns are fitted on deck, on the bridges, and in the military tops, four of them also being mounted on what is rather a novelty in naval construction, a gallery running round the outside of the funnel, which was fitted when the ship was under repairs some months ago.
There are three electric light projectors, one forward on the upper deck, one on the bridge just forward of the funnel, and one in the mizzen top." (1881 Scientific American)
Redoutable was present during the negotiation of the treaty of the 7 September 1901 with China.
All-steel warships were later built by the Royal Navy, with the dispatch vessels Iris and Mercury, laid down in 1875-1876.