Second generation: the turreted ironclad

An audacious attempt to combine the rotating artillery turret with the traditional type of ship was effectuated on the HMS Captain, a modified three-masted sailing ship. The sides and ceiling of the gun deck were removed in the space between the mizzen mast and the fore mast, and two turrets were installed on the centerline of that space. A corridor running along the centerline, above the turrets, allowed the transit between the forecastle and the stern. Unfortunately the HMS Captain suffered from a very deficient stability and during a storm she capsized and sank, taking with her the whole complement, which included Captain C. P. Coles, inventor of the rotating artillery turret and the experimental ship that claimed his life.

For his part, chief engineer E. J. Reed, who had tried to dissuade the Admiralty from the construction of the HMS Captain, believed that rotating turrets would be more effective and hulls would have enough stability by just removing the traditional sail rig. The result of this conception was the HMS Devastation, launched in 1871, which constituted a hard blow for those who had supported at all costs the necessity of sails in oceanic ships. The HMS Devastation had a length 86.9 meters, a beam of 19.6 meters, a draught of 8.2 meters and two screw propellers which allowed a maximum speed of 12.5 knots. The very small length to beam ratio that characterized this ship - and also her successors - was intended as well to improve stability.

British ironclad HMS Devastation
The HMS Devastation was armed with four 305-millimeter muzzle-loading rifled cannons, installed on two turrets armored with plates of 254-356 millimeters in thickness, while the armor on the hull was of 216-305 millimeters. So, while her dimensions were rather modest, the HMS Devastation had a standard displacement of 9330 tonnes. The necessity of loading the cannons through their muzzles was a shortcoming, as this did not allow to extend their tubes far beyond the turret walls, but nonetheless the HMS Devastation was in that moment the most powerful and effective warship ever built, serving as model for many later others.

Since the time of the Napoleonic Wars, Great Britain had been the main naval power in the world, but due to motives of foreign policy, the Royal Navy would rearm itself only if a foreign naval power did so. In 1871, Armstrong declared that cannons of larger caliber than those in service could be produced, but the Admiralty did not take the chance. Eventually, it was Italy the first nation that built battleships armed with cannons of huge caliber. The Italian projectist Benedetto Brin combined the largest cannons with the highest speed possible, building the Caio Duilio and the Enrico Dandolo for the sole purpose of carrying four of those giant cannons, each of which weighed 38 tonnes. But Armstrong informed that 381-millimeter cannons weighing 51 tonnes could be delivered and the Italians accepted the offer. In the new Italian battleships the turrets were arranged in echelon so they could fire, more or less, in any direction.

Italian ironclad Caio Duilio
The dimensions of these ships were 103.9 meters in length, 19.7 meters in beam and 8 meters in draught, with a normal displacement of 11140 tonnes. The cannons were not the only gigantic feature in these ships, as their armored belt had a thickness of 550 millimeters in the waterline, while the armor on the turrets had 450 millimeters. The two screw propellers were intended for a maximum speed of 15 knots. As these battleships significantly surpassed the characteristics of the HMS Devastation, Great Britain promptly replied by building the HMS Inflexible, which had a displacement of 11880 tonnes and a waterline armor with the incredible thickness of 609 millimeters, and was armed with four 406-millimeter cannons of 80 tonnes each. But, in a bold move, Italy replied by ordering from Armstrong four 450-millimeter cannons of 100 tonnes each for the Caio Duilio.

In the decade of 1881-1890 heavy breech-loading cannons were introduced, as it had been demonstrated the superior effectiveness of projectiles when flying at higher muzzle speeds; this could be achieved by means of slow powders and much longer cannons. The length of the tubes was a drawback for reloading through the muzzle and because of this cannons of large caliber were made of the breech-loading type. This meant the obsolescence of the turrets of older type and the new cannons started to be installed in barbettes. In barbetted turrets the tubes of the cannons were left unprotected and only when the piece was reloaded the breech descended into the turret. As an early example, the French coastal battleships of the Caiman class, built in 1885, had two 420-millimeter cannons installed in barbettes.

French coastal battleship Caiman
In 1885 the Italians launched the Andrea Doria, one of their last ironclads which had the turrets emplaced amidships following an echelon type of arrangement. However, this ship and her two sisters presented significant improvements over preceding classes, as they were armored with steel and armed with breech-loading cannons. These weapons, built by Armstrong as well, were of caliber 432 millimeters, had 27 calibers in length and weighed 108 tonnes. They could fire a 908-kilogram projectile every four minutes, propelled by a 420-kilogram charge and able to pierce 210 millimeters of armor. The huge caliber was a drawback in that it caused a low rate of fire. In these new battleships the cannons were mounted in turrets of a renewed design, which featured inclined armor to help divert the projectiles.

Following a conventional scheme, there was a central citadel under the turrets protecting the machinery and the artillery. The lower section of the citadel was at the level of the armored belt and ran on a length of about 50 meters amidships, being delimited by two transversal bulkheads placed next to the outer face of each funnel. The upper section of the citadel, which protected the mechanisms of the cannons, offered a similar level of protection but limited to a length of only 28 meters. The adoption of steel allowed to moderate the thickness of the armor in comparison to previous designs; the main belt had 450 millimeters in thickness while the bulkheads, barbettes and turrets had 360 millimeters. Built like this, the Andrea Doria had a normal displacement of 9886 tonnes, with a length of 105.9 meters, a beam of 19.8 meters and a draught of 8.3 meters.

The machinery featured two vertical double-expansion steam engines, each driving a single screw propeller, with steam supplied by eight coal-fired cylindrical boilers. The engines produced 10500 horsepower and could impulse the ship at a top speed of 16.1 knots. With her full load of 850 tonnes of coal the Andrea Doria had an operational range of 2800 nautical miles at 10 knots. Another interesting characteristic of the project was the inclusion of four 356-millimeter torpedo tubes, two on the stern and another two on the prow below the waterline, a type of armament which had been already installed on the ships of the Caio Duilio class ten years before.

These early Italian battleships, despite being so different from any other former or later warship design, represented the summit of technology in the decades of 1870 and 1880; they transmitted then such a sense of power that the American senator Bonjean said that the Caio Duilio alone could have destroyed the whole United States Navy. These battleships were appreciated as well by France and, specially, by Great Britain, whose Royal Navy tried to build its own turreted ironclads. Meanwhile, Italy continued building more of them. But even if the Caio Duilio class had been built following vanguard criteria, naval technology had progressed much when the Roger di Laurio class - to which the Andrea Doria belonged - was in construction. The ships with turrets arranged in echelon had been outclassed by those ships which had their turrets mounted on the fore and aft decks.

Italian ironclad Andrea Doria
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