also exposed the gun's crew to greater danger from hostile fire. In addition, since the barbette position would be higher than a casemate position—that is, a gun firing through an embrasure—it would generally have a greater field of fire. The American military theorist Dennis Hart Mahan suggested that light guns, particularly howitzers, were best suited for barbette emplacements since they could fire explosive shells and could be easily withdrawn when they came under enemy fire. Fortifications in the 19th century typically employed both casemate and barbette emplacements. For example, the Russian outside Sevastopol was equipped with 43 heavy guns in its seaward side during the Crimean War in the mid-1850s; of these, 27 were barbette mounted, with the rest in casemates. A modified version of the barbette type was the disappearing gun, which placed a heavy gun on a carriage that retracted behind a parapet for reloading; this better protected the crew, and made the gun harder to target, since it was only visible while it was firing. The type was usually used for coastal defence guns. As naval gun turrets improved to allow greater elevation and range, many disappearing guns, most of which were limited in elevation, were seen as obsolescent; with aircraft becoming prominent in the First World War, they were largely seen as obsolete. However, they remained in use through the early Second World War, at least by the United States, due to limited funding for replacement weapons between the wars. Later heavy coastal guns were often protected in hybrid installations, in wide casemates with cantilevered overhead cover partially covering a barbette or gunhouse mount. Use in warships Following the introduction of ironclad warships in the early 1860s, naval designers grappled with the problem of mounting heavy guns in the most efficient way possible. The first generation of ironclads employed the same broadside arrangement as the old ship of the line, but it was not particularly effective for ahead or stern fire. This was particularly important to designers, since the tactic of ramming was revived following its successful employment at the decisive Austrian victory at the Battle of Lissa in 1866. Ramming required a ship to steam directly at its opponent, which greatly increased the importance of end-on fire. Designers such as Cowper Phipps Coles and John Ericsson designed the first gun turrets in the 1860s, which gave the guns a wide field of fire. These turrets