For thousands of years, warships were built of wood and powered by human muscles and the wind. Gunpowder carved the first niche for chemical energy and machine-made materials, but successfully mounting and using cannons aboard ships still required vast amounts of time and muscle power.
In the mid-nineteenth century, however, naval warfare changed dramatically and so innovation was needed. This innovation came in the form of the ironclad warship. The Crimean War produced halting steps toward mechanized combat at sea, but not until the American Civil War did a navy conduct a campaign fought from start to finish by seagoing machines.
The first ironclads, developed in Europe by the French, were merely the standard ship design of the time with added metal plates on the side to protect against deadlier artillery. These designs jumped the Atlantic Ocean to see use in the American Civil War, where they were refined and changed to accommodate the shallower western riverfronts where many naval battles took place.
Steamboats outfitted with metal plates saw use in battle, and the Union forces eventually developed the gunship that is now synonymous with the word “ironclad.” These steam-powered ships sat somewhat low in the water and were nearly completely covered with heavy plating, making them quite impervious to standard gunfire, artillery, and even cannon fire.
At the outbreak of the war, the US Navy did not have any ironclad warships, but most of the US Navy remained loyal to the Union. To overcome this disadvantage, the Confederacy decided to pursue the construction and purchase of ironclads as a way to gain some sort of naval advantage.
In response to this effort, the Union began building their own ironclads. This included two main styles, the ocean-going Monitor class ironclads and City class ironclads used for river warfare.
Fleets utilizing the ironclad could finally go toe-to-toe with armored forts, and in March of 1862, at the Battle of Hampton Roads in Virginia, the world saw its first naval engagement between opposing ironclad forces. The USS Monitor and the CSS Virginia (formerly the steam frigate USS Merrimack) dueled until Virginia retreated, neither side able to inflict serious damage to the other.
The Civil War saw more ironclads built by both sides, and they played an increasing role in the naval war alongside the unarmored warships, commerce raiders, and blockade runners. The Union built a large fleet of fifty monitors modeled on their namesake.
The Confederacy built ships designed as smaller versions of Virginia, many of which saw action, but their attempts to buy ironclads overseas were frustrated as European nations confiscated ships being built for the Confederacy – especially in Russia, the only country to openly support the Union through the war. Only CSS Stonewall was completed, and she arrived in American waters just in time for the end of the war.
The exploits of ironclad warships, on both sides, proved without a doubt that the age of the wooden ship-of-war was over. The Battle of Mobile Bay really made the point clear. Despite having 11 wooden ships, the Union needed its Monitor class ironclads to take a large confederate ironclad, the CSS Tennessee.
By the end of the Civil War, the rest of the world had taken notice. Everyone was trying to bring their navies up to date as the old wooden ships became obsolete, and 1864 marked the last major naval engagement between squadrons of wooden ships.
(Photo credit: Archive Photos / Library of Congress / Buyenlarge / Getty Images).