An ironclad was a steam-propelled warship in the early part of the second half of the 19th century, protected by iron or steel armor plates. The ironclad was developed as a result of the vulnerability of wooden warships to explosive or incendiary shells. The first ironclad battleship, La Gloire, was launched by the French Navy in November 1859. The British Royal Navy had been considering armoured warships since 1856 and prepared a draft design for an armoured corvette in 1857, however in early 1859 the Royal Navy started building two iron-hulled armoured frigates, and by 1861 had made the decision to move to an all-armoured battlefleet. After the first clashes of ironclads (both with wooden ships and with one another) took place during the American Civil War, it became clear that the ironclad had replaced the unarmored ship of the line as the most powerful warship afloat. This type of ship would come to be very successful in the American Civil War.
Four ironclads were built for the USE Navy. They were originally planned and named under the New United States, as part of the Confederated Principalities of Europe, but the CPoE had become the USE by the time they were ready to launch. The names were kept, though "USS" was replaced with "SSIM".
Eddie Cantrell's original idea was for three ironclads, but they would have been armored against 19th century artillery. Cutting the armor thickness in half allowed an extra ship to be built, while still leaving them adequately protected against 17th century guns. Their armor was made from salvaged railroad rails, and only a limited number of them could be allocated to the ironclads.
The ironclads also had trim tanks which allowed their draft to be adjusted at need. They used hydro-jet propulsion provided by diesel-powered pumps. This avoided the dangers of steam, was less vulnerable to damage than a propeller, and made them very maneuverable, but was also another factor which limited the number that could be made.
The ironclads carried three carronades, but their main weapons were a pair of ten-inch guns that were primarily useful for shore bombardment.
The USE Navy's ironclads were: