barbette

Barbettes are several types of gun emplacement in terrestrial fortifications or on naval ships.

In recent naval usage, a barbette is a protective circular armour support for a heavy gun turret. This evolved from earlier forms of gun protection that eventually led to the pre-dreadnought. The name ''barbette'' ultimately comes from fortification - it originally meant a raised platform or mound, as in the French phrase ''en barbette'', which refers to the practice of firing a cannon over a parapet rather than through an embrasure in a fortification's casemate. The former gives better angles of fire but less protection than the latter. The disappearing gun was a variation on the barbette gun; it consisted of a heavy gun on a carriage that would retract behind a parapet or into a gunpit for reloading. Barbettes were primarily used in coastal defences, but saw some use in a handful of warships, and some inland fortifications. The term is also used for certain aircraft gun mounts.

Shipboard barbettes were primarily used in armoured warships - starting in the 1860s during a period of intense experimentation with other mounting systems for heavy guns at sea. In these, gun barrels usually protruded over the barbette edge, so barbettes provided only partial protection, mainly for the ammunition supply. Alternatives included the heavily-armoured gun turret and an armoured, fixed central gun battery. By the late 1880s, all three systems were replaced with a hybrid barbette-turret system that combined the benefits of both types. The armoured vertical tube that supported the new gun mount was referred to as a barbette.

Guns with restricted arcs of fire mounted in heavy bombers during World War II—such those in the tail of the aircraft, as opposed to fully revolving turrets—were also sometimes referred to as having barbette mounts, though usage of the term is primarily restricted to British publications. American authors generally refer to such mounts as tail guns or as tail gun turrets.

Use in fortifications

The use of barbette mountings originated in ground fortifications. The term originally referred to a raised platform on a rampart for one or more guns, enabling them to be fired over a parapet. This gave rise to the phrase ''en barbette'', which referred to a gun placed to fire over a parapet, rather than through an embrasure, an opening in a fortification wall. While an ''en barbette'' emplacement offered wider arcs of fire, it 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 were exceedingly heavy, which required them to be placed low in the ship to reduce top-weight—and produced a dangerous tendency to capsize in heavy seas, amply demonstrated by the loss of and Coles himself with the ship in a gale

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