Why wood stopped being enough
For centuries a wooden warship could take a great deal of punishment. Solid iron shot often lodged in thick oak timbers, and a hull could remain afloat after a long battle. Two developments in the early nineteenth century weakened that advantage. The first was the shell gun, which fired explosive shells on a flat trajectory and caused fires and splintering. Its effectiveness was shown in 1853, when a Russian squadron destroyed an Ottoman force at Sinope. The second was the steam engine, which freed ships from the wind and made it practical to carry heavy armour.
In the Crimean War, the French built armoured floating batteries which were used against Russian fortifications at Kinburn in 1855. Their iron plate shrugged off a great deal of fire. This persuaded naval planners that armour could be applied to ships meant for open water as well.
The first ocean-going ironclads
France led. Its steam battleship La Gloire, launched in 1859, was a wooden-hulled ship covered with iron armour plate, and it was generally treated as the first ocean-going ironclad battleship. Britain, which did not want to see French naval strength grow unanswered, responded with HMS Warrior, launched in 1860. Warrior was larger and was built with an iron hull as well as armour. Her construction drew on the broader changes described under iron shipbuilding, which was transforming merchant and naval yards alike.
These ships still carried sails, and their guns were mounted in a broadside like earlier battleships. They were not an immediate break from the past so much as an upgrade, but their effect was dramatic. A wooden ship of the line of earlier generations, however grand, could not fight them on equal terms. Fleets that had taken decades to build were largely outdated within a few years, and most navies had to decide quickly whether to convert old hulls or build new ones.
Hampton Roads
The American Civil War provided the best-known test. The Union blockade of Confederate ports relied on wooden warships. The Confederacy converted the burned hull of the steam frigate USS Merrimack into CSS Virginia, covering a sloping casemate with iron plate. On 8 March 1862 she attacked the Union squadron in Hampton Roads, Virginia, and destroyed two wooden ships, USS Cumberland and USS Congress.
The next day, the Union ironclad USS Monitor, designed by John Ericsson, arrived. She was a low, flat vessel with a rotating gun turret, and her appearance was very different from Virginia’s. The two ships fought for hours on 9 March at close range, and neither could seriously damage the other. The battle is usually described as a draw, though the Union side had the advantage that the blockade held.
The fight was significant less for its outcome than for what it showed. Armoured ships were far harder to damage with the guns then in service, and wooden ships could not face them. The Monitor’s turret, which allowed guns to be aimed independently of the ship’s heading, became an important idea in later battleship design. Virginia was destroyed by her own crew in May 1862 when Norfolk was abandoned, and Monitor foundered in a gale off Cape Hatteras at the end of that year.
Ramming and the Battle of Lissa
Another lesson was drawn from the Battle of Lissa in 1866 between Austria and Italy. The Austrian commander, Wilhelm von Tegetthoff, led a fleet that included ironclads and used ramming tactics, and the Austrian flagship rammed and sank the Italian ship Re d’Italia. The result encouraged many navies to put rams on their warships for decades afterwards, even though later experience showed ramming to be risky and uncommon. The revival of a weapon from the age of oared galleys shows how the old and new were mixed in this period.
The race of armour and guns
After the 1860s, naval design became a contest between armour and guns. Heavier plate led to heavier guns, which led to still thicker armour. Turrets spread, masts gradually disappeared, and iron gave way to steel. Wooden warships that stayed afloat were relegated to secondary tasks such as harbour service or training, and the great era of wood in naval service came to an end. The rise of the steamship era made the transition easier because the same changes were taking place in the merchant fleet.
The ironclad is sometimes treated as a brief stage between sail and the modern battleship, but it was something more. It established the basic principle that a warship should be judged by its protection as well as by its guns. That principle, together with steam and turrets, led by stages to the battleships of the early twentieth century, including the all-big-gun designs discussed in the history of the dreadnought.