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.
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, they were largely seen as obsolete.
Later heavy coastal guns were often protected in hybrid installation, with wide casemate with cantilevered overhead cover partially covering a barbette mount.
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 HMS Captain and Coles himself with the ship in a gale in 1870.
In the 1870s, designers began to experiment with an en barbette type of mounting. The barbette was a fixed armoured enclosure protecting the gun. The barbette could take the form of a circular or elongated ring of armour around the rotating gun mount over which the guns (possibly fitted with a gun shield) fired. The barbette system reduced weight considerably, since the machinery for the rotating gun mount, along with the mount itself, was much lighter than that required for the gun house of a turret. The savings in weight could then be passed on to increase armour protection for the hull, improve coal storage capacity, or to install larger, more powerful engines. In addition, because barbettes were lighter, they could be placed higher in the ship without jeopardizing stability, which improved their ability to be worked in heavy seas that would have otherwise rendered turrets unusable. This also permitted a higher freeboard, which also improved seakeeping.
Ironclads equipped with barbettes were referred to as "barbette ships" much like their contemporaries, turret ships and central battery ships, which mounted their heavy guns in turrets or in a central armored battery. Many navies experimented with all three types in the 1870s and 1880s, including the British Admiral-class battleships, the French Marceau-class ironclads, the Italian Italia-class battleships, and the German Sachsen-class ironclads, all of which employed barbettes to mount their heavy guns. All of these navies also built turret and or central battery ships during the same period, though none had a decisive advantage over the other. The British and the Russian navies experimented with using disappearing guns afloat, including on the British HMS Temeraire and the Russian monitor Vitse-admiral Popov and some of the Ekaterina II class battleships. They were not deemed particularly successful and were not repeated.
In the late 1880s, the debate between barbette or turret mounts was finally settled. The Royal Sovereign class, mounted their guns in barbettes, but the follow-on design, the Majestic class, adopted a new mounting that combined the benefits of both kinds of mounts. A heavily armoured, rotating gun house was added to the revolving platform, which kept the guns and their crews protected. The gun house was smaller and lighter than the old-style turrets, which still permitted placement higher in the ship and the corresponding benefits to stability and seakeeping. This innovation gradually became known simply as a turret, though the armored tube that held the turret substructure, which included the shell and propellant handling rooms and the ammunition hoists, was still referred to as a barbette. These ships were the prototype of the so-called pre-dreadnought battleships, which proved to be broadly influential in all major navies over the next fifteen years.
Ships equipped with barbette mountings did not see a great deal of combat, owing to the long period of relative peace between their appearance in the 1870s and their obsolescence in the 1890s. Some barbette ships saw action during the British Bombardment of Alexandria in 1882, and the French ironclad Triomphante participated in the Battle of Fuzhou during the Sino-French War in 1884. The two Chinese ironclads, Dingyuan and Zhenyuan, that took part in the Battle of the Yalu River during the First Sino-Japanese War in 1894, carried their main battery in barbettes, though they were equipped with extensive gun shields that resembled turrets. The shields were nevertheless only proof against small-arms fire. Three of their opponents at the Yalu River, the Japanese Matsushima-class cruisers, also mounted their guns in open barbettes. Those barbette ships that survived into World War I were typically used only for secondary purposes. For example, the French Marceau was used as a repair ship for submarines and torpedo boats, while the German Württemberg was employed as a torpedo training ship. A handful of barbette ships did see action during the war, including the British Revenge, which bombarded German positions in Flanders in 1914 and 1915.
When applied to military aircraft, largely in aviation history books written by British historians, a barbette is a position on an aircraft where a gun is in a mounting which has a restricted arc of fire when compared to a turret, or which is remotely mounted away from the gunner. As such it is frequently used to describe the tail gunner position on bombers such as the Boeing B-17 Flying Fortress, with American aviation books frequently describing the position as a tail gun turret, or simply as a tail gun.
The term "barbette" is also used by some, again primarily British historians, to describe a remotely aimed and operated gun turret emplacement on almost any non-American military aircraft of World War II, but it is not usable in a direct translation for the German language term used on Luftwaffe aircraft of that era. As an example, the German Heinkel He 177A heavy bomber had such a remotely operated twin-MG 131 machine gun Fernbedienbare Drehlafette FDL 131A powered forward dorsal gun turret, with the full translation of the German term comprising the prefix as "Remotely controlled rotating gun mount".