The Union gun-boats at Shiloh on the evening of the first day / H.M. Eaton.

After first battles involving of American ironclads (both with wooden ships and with one another) in 1862 during the American Civil War, it became clear that the ironclad had championed the unarmored ship as the most powerful warship. This type of ship would come to be very successful in the American Civil War. This change was pushed forward by the development of heavier naval guns (the ironclads of the 1880s carried some of the heaviest guns ever mounted at sea at the time), more sophisticated steam engines, and advances in metallurgy which made steel shipbuilding possible. An ironclad is a steam-propelled warship protected by iron or steel armor plates used in the early part of the second half of the 19th century. The ironclad was developed as a result of the vulnerability of wooden warships to explosive or incendiary shells. The first ironclad battleship, Gloire, was launched by the French Navy in November 1859. In early 1859 the Royal Navy started building two iron-hulled armored frigates, and by 1861 had made the decision to move to an all-armored battle fleet. The rapid development of warship design in the late 19th century transformed the ironclad from a wooden-hulled vessel that carried sails to supplement its steam engines into the steel-built, turreted battleships and cruisers of the 20th century.

The first recorded sea battle occurred about 1210 BC: Hittites defeated and burned the Cyprus fleet. Athens protected itself from Persia by building a fleet paid for by silver mines profits. Romans developed the technique of grappling and boarding enemy ships with soldiers. Constantinople invented a Greek fire, a flamethrower to burn enemy's ships. Torpedo was invented by the Arab Hasan al-Rammah in 1275. With the Age of Discovery, naval actions in defense of the new colonies grew in scale. In 1588, Spain sent Armada to subdue the English fleet of Elizabeth, but Admiral Sir Charles Howard won the battle, marking the rise of the Pax Britannica. Anglo-Dutch Wars were the first wars to be conducted entirely at sea. Most memorable of these battles was the raid on the Medway, in which the Dutch sailed up the river Thames, and destroyed most of the British fleet. The 18th century was a period of continuous naval wars, in the Mediterranean, in the Atlantic Ocean, and in the Baltic Sea. The Napoleonic Wars culminating in the Battle of Trafalgar in 1805. With the advent of the steamship, it became possible to create massive gun platforms and to provide them with heavy armor protection. The battle of the CSS Virginia and USS Monitor in the American Civil War that symbolized the changing times. In the 20th century, the steel-armored battleships with large shell turret guns emerged. The Russo-Japanese Battle of Tsushima in 1905 was the first test of the new concepts, resulting in Japanese victory. Airpower became key to navies throughout the 20th century, moving to jets launched from ever-larger carriers, and augmented by cruisers armed with guided missiles and cruise missiles. During the Pacific War of World War II, the carriers and their airplanes were the stars and the United States became the world's dominant sea power. The Falklands War, however, showed the vulnerability of modern ships to sea-skimming missiles. Parallel to the development of naval aviation was the development of submarines. In the 1950s the Cold War inspired the development of ballistic missile submarines.