Although not a generally accepted hypothesis, some postulate that the first instance of an ironclad warship may have been a ship designed by General Qin Shifu during the Song Dynasty in 1203. Some Chinese historical records credit Qin Shifu with the invention of a ship that was shaped like a Falcon, which had sheet-iron armor and an iron ram.

Korean turtle ships (Hangul:거북선, Geobukseon or Kobukson) of Korea are first mentioned in records from 1413 and 1415 in the Annals of Joseon Dynasty, though the actual design of the ships, and whether they used iron armor, is unclear. The usage of iron plates with Turtle ships is only documented at the end of the following century, during the 1592-1598 Imjin War with Japan.


In 1576, the Japanese daimyo Oda Nobunaga had six partially iron-covered war ships (Ōatakebune) constructed. These ships were called "Tekkousen" (鉄甲船, literally "iron armored ships"), were armed with multiple cannons and large caliber rifles, and are described by contemporary Jesuit sources as being protected by iron plates 2-3 inches thick.•
Nobunaga defeated the navy of his enemy Mori Motonari with these ships at the mouth of the Kizu River, Osaka in 1578 with a successful naval blockade. Despite being regarded as floating fortresses, they were used as warships in the Seven-Year War with Korea. The most notable and largest of these ships was the Nihon Maru, which briefly fought a Korean turtle ship in the battle of Angolp'o harbor in 1592.


Detailed records are available for the Turtle ships said to have been resurrected by the Korean naval leader Admiral Yi Sun-sin prior to the Imjin War (also known as the Seven-Year War) of 1592-1598 between Korea and Ming Dynasty China versus Japan. These geobukseon do not seem to have had side armor, but instead had a roof covered in iron plates, giving the ships a turtle-like appearance. The armor plates of the roof had sharp retractable iron spikes, making the primary Japanese tactic of grappling and boarding an opposing ship much less effective. The turtle ships were armed with an average of ten long-range cannons on each side and two larger guns to the stern and bow, supplemented by archers firing flaming arrows out of portholes. Retractable sails and oars made for a small profile, and a dragon's head structure at the bow served as a gunport and could also emit sulfur fumes as a smokescreen and irritant. Turtle ships were put to use once again against the Russian fleet thirty years after the Seven-Year War.

At the Battle of Sinope in 1853, the Russian Black Sea Fleet, equipped with newly developed Paixhans guns using explosive shells, destroyed a flotilla of wooden Turkish ships with contemptuous ease. This early engagement of the Crimean War signaled the necessity of iron armor to the navies of the world. During the war, the French and British navies collaborated on the design of ironclad floating batteries for reducing Russian defenses which had previously held off attempts at bombardment by wooden hulled battleships. The French used theirs in 1855 against the defenses at Kinburn on the Black Sea. The British were delayed in bringing their batteries to the Baltic Sea to use against Kronstadt in 1856 and the war ended before they were used.

In 1859, France launched La Gloire, the first ocean-going ironclad warship in history. Designed by the famous naval architect Dupuy de Lôme, she was wooden hulled and covered with iron plates. The French would have gone for an iron hull but their industry was not at the time able to manage it. It was launched in an attempt to gain a naval edge over the British, but the French were unable to maintain their technical and quantitive lead. In the following year and nine months later than planned, the British Royal Navy launched the iron-hulled and armored HMS ''Warrior'', and the ''Black Prince'' in 1861. Although La Gloire was developed as a ship of the line, in effect a battleship cut to one deck due to weight considerations, the larger Warrior was classified as an armored frigate.

France proceeded to construct 16 ironclad warships, including two more sister ships to La Gloire, and the only two-decked broadside ironclads ever built, the Magenta and the Solferino, which were also the first warships to be equipped with a spur ram. Only two of these ships were iron-hulled. In the meantime, Britain continued building large armored frigates, often as powerful and more seaworthy than the French ironclads.

The first use of steam-powered ironclads in combat was in the American Civil War. The first of these vessels to see action in October 1861, the CSS ''Manassas'', was a turtleback ironclad ram formerly known as Enoch Train steam-tug. She was used in combat against the U.S. Navy and proved somewhat effective initially until U.S. ships learned to exploit her rather weak armor.


The first engagement of two ironclad warships was the Battle of Hampton Roads, from March 8-9, 1862. Though the engagement was inconclusive, the Confederate ironclad CSS ''Virginia'' and her novel Federal counterpart, USS ''Monitor'', became somewhat legendary, and helped to usher in a new age of armored, steam powered warships. The Virginia was built using the remains of the scuttled, wooden-hulled USS ''Merrimack'', and is often referred to the Merrimack, even in her Confederate ironclad incarnation.

The Monitor, with its rotating turret and extremely low profile, was a revolutionary design for a warship. After it had proven its capability, the U.S. built a number of "monitor-class ships", as they became known; many seeing use as river monitors. The use of monitor ships spread quickly throughout the world after the war. John Ericsson, the designer of the USS Monitor, returned to his native Sweden and constructed similar ships for the Swedish Navy.

Spain used ironclads against Chilean and Peruvian ports from 1864 to 1866, destroying the fortress at El Callao (see Battle of Callao), and the ironclad Numancia was the first to circumnavigate the world (arriving in Cádiz on September 20 1867, and earning the motto: "Enloricata navis que primo terram circuivit"). The largest battle involving ironclads of this type was the battle of Lissa, in 1866. Waged between the Austro-Hungarian and Italian navies, the battle pitted combined fleets of wooden frigates and corvettes and ironclad warships on both sides in the largest European naval battle since the Battle of Trafalgar. The victory won by Austria-Hungary established it briefly as the predominant naval power in the Mediterranean. Ironclads were also used by both Peru and Chile in the War of the Pacific in 1879.


The ironclad continued to be the dominant style of warship and developed into what is sometimes called the "old" battleship before being replaced by more advanced, far more seaworthy vessels known to history as pre-dreadnoughts. Among the types of ironclad were monitors (patterned after the USS ''Monitor''), protected cruisers, armored cruisers and armored gunboats.

While the ironclad warship suffered from numerous flaws, the fact that it became the prominent naval weapon of its era and inspired nearly a century of progressively heavier armored warships can be ascribed to its massive advantage over the previous ships of the line in terms of protection. While a ship of the line could resist some damage, it was terribly vulnerable to fire and found itself completely outclassed by the new developments in naval armament beginning in the middle of the nineteenth century. Combined with steam engine propeller propulsion, the ironclad warship could outfight, outgun, and eventually outrun even the most powerful three decker.

The age of the ironclad as a main line battle craft came to an end around 1890, as iron- or steel-hulled pre-dreadnought battleships were developed and deployed.