The modern equivalent of, and the name derived from, the older sailing ship of the line.
From Ship of the Line to ‘Ironclad’.
The introduction into warfare at sea during the 1840s and 1850s of the high-explosive shell, the rifled gun, armour plate, and steam propulsion of acceptable reliability made obsolete the traditional three-decker wooden sailing ship of the line. However, the transition from ship of the line to battleship was a comparatively gradual process, many of the old sailing first rates being converted to have iron protection on their hulls and lengthened to take steam propulsion, while the new iron ships retained the masts, sails, and gun batteries of the older wooden ships. It was only with the growth in reliability and radius of action of the steam engine, and the introduction of the breech-loading gun and a more efficient propellant than black powder, that the battleship at last broke clear from its wooden predecessor and evolved as a type of its own.
The first seagoing ‘ironclad’, the precursor to the 20th-century battleship, was the French Gloire, and she was followed in 1860 by the British iron-hulled HMS Warrior. Though classed as frigates, these 13-knot men-of-war, powered by engines of over 3,000 horsepower but also carrying a full sailing rig, could overtake and overwhelm any contemporary three-decker ship of the line.
The first battleships to rely entirely on steam propulsion were known as mastless ships, though another feature, the ram bow, lingered on longer than sails. The first such ship was the 9,300-ton British Devastation, designed in 1869. Having a very low freeboard, and without forecastle or poop, she was virtually a seagoing monitor. Here, again, the two types overlapped considerably in time, the masted iron battleships lasting until nearly 1890.
Guns, armour, and steam machinery improved so rapidly during the period 1870–1900 that the battleship began to settle down into a recognizable type, with the main guns mounted in turrets, and most navies began to build them in classes instead of singly. Tonnage increased with each new ship, in Britain rising to the 15,000 tons of the Majestic, completed in 1896.
By the last decade of the 19th century every permutation of large and small guns, high and moderate speed, thick and thin armour plate, had seemingly been exhausted, naval architecture had settled on a basic specification for the battleship, and the term ‘ironclad’ had been dropped. This combined an armament of four big guns, about ten guns of various smaller calibre, and a large number of quick-firers to deal with the new threat to the battleship, the torpedo boat.
In 1903 the naval annual Fighting Ships published an article by the distinguished Italian naval architect Vittorio Cuniberti, entitled ‘An Ideal Battleship for the British Fleet’, which called for a vessel combining an armament of twelve 12-in. (30-cm) guns, 12 inches of armour plate, and a speed of 24 knots—an unprecedented combination of qualities. HMS Dreadnought which was launched in 1906 fell only marginally short of Cuniberti's ideal. She overturned all the long-established principles of compromise in naval architecture, made every other battleship in the world obsolete, and created a furore in Britain as well as the world at large. She had many progenitors, but history justly gives the first credit to Admiral Sir John Fisher. With her armament of ten 12-in guns, displacement of 17,900 tons, and maximum speed of 21 knots, Dreadnought's superiority to any other fighting ship was so manifest that no naval power could afford to build to any other pattern. Moreover, she was powered by turbine machinery (see steam propulsion), which offered greatly superior dependability, simplicity, and cleanliness. Such an advance in design was achieved that it was not imitated by foreign designers for several years and kept Britain ahead in what became known as the ‘Dreadnought Race’ for supremacy at sea.