ship from ramming or to make a torpedo attack by a boat less suicidal. A more practical and influential weapon was the self-propelled or Whitehead torpedo. Invented in 1868 and deployed in the 1870s, it formed part of the armament of ironclads of the 1880s like HMS Inflexible and the Italian . The ironclad's vulnerability to the torpedo was a key part of the critique of armored warships made by the school of naval thought; it appeared that any ship armored enough to prevent destruction by gunfire would be slow enough to be easily caught by torpedo. In practice, however, the Jeune Ecole was only briefly influential and the torpedo formed part of the confusing mixture of weapons possessed by ironclads. Armor and construction The first ironclads were built on wooden or iron hulls, and protected by wrought iron armor backed by thick wooden planking. Ironclads were still being built with wooden hulls into the 1870s. Hulls: iron, wood, and steel Using wrought iron construction for warships offered advantages for the engineering of the hull. However, unarmored iron had many military disadvantages, and offered technical problems which kept wooden hulls in use for many years, particularly for long-range cruising warships. Iron ships had first been proposed for military use in the 1820s. In the 1830s and 1840s, France, Britain and the United States had all experimented with iron-hulled but unarmored gunboats and frigates. However, the iron-hulled frigate was abandoned by the end of the 1840s, because iron hulls were more vulnerable to solid shot; iron was more brittle than wood, and iron frames more likely to fall out of shape than wood. The unsuitability of unarmored iron for warship hulls meant that iron was only adopted as a building material for battleships when protected by armor. However, iron gave the naval architect many advantages. Iron allowed larger ships and more flexible design, for instance the use of watertight bulkheads on the lower decks. Warrior, built of iron, was longer and faster than the wooden-hulled Gloire. Iron could be produced to order and used immediately, in contrast to the need to give wood a long period of seasoning. And, given the large quantities of wood required to build a steam warship and the falling cost of iron, iron hulls were increasingly cost-effective. The main reason for the French use of wooden hulls for the ironclad fleet built in the 1860s was