Barbette armour

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 ultimately comes from fortification, originally meaning a raised platform or mound, seen in the French phrase en barbette, which refers to the practice of firing a cannon over a parapet rather than through an embrasure in the fortification. 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. They 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; alternatives included the heavily armored gun turret and an armored, 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 heavily-armored 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 simply as tail guns or tail gun turrets.

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 Fort Constantine outside Sevastopol was equipped with 43 heavy guns in its seaward side during the Crimean War in the mid-1850s; of these, 27 were in barbettes, with the rest in casemates.

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