ARTILLERY

in military science, crew-served big guns, howitzers, or mortars having a calibre greater than that of small arms, or infantry weapons. Rocket launchers are also commonly categorized as artillery, since rockets perform much the same function as artillery projectiles, but the term artillery is more properly limited to large gun-type weapons using an exploding propellant charge to shoot a projectile along an unpowered trajectory. For three centuries after the perfection of cast-bronze cannon in the 16th century, few improvements were made in artillery pieces or their projectiles. Then, in the second half of the 19th century, there occurred a series of advances so brilliant as to render the artillery in use when the century closed probably 10 times as efficient as that which marked its opening. These remarkable developments took place in every aspect of gunnery: in the pieces, with the successful rifling of cannon bores; in the projectiles, with the adoption of more stable elongated shapes; and in the propellants, with the invention of more powerful and manageable gunpowders. These advances wrought a further transformation in the ever-changing nomenclature and classification of artillery pieces. Until the adoption of elongated projectiles, ordnance was classified according to the weight of the solid cast-iron ball a piece was bored to fire. But, because cylindrical projectiles weighed more than spheres of the same diameter, designation in pounds was abandoned, and the calibre of artillery came to be measured by the diameter of the bore in inches or millimetres. Cannon became the general term for large ordnance. A gun was a cannon designed to fire in a flat trajectory, a howitzer was a shorter piece designed to throw exploding shells in an arcing trajectory, and a mortar was a very short piece for firing at elevations of more than 45. in military science, crew-served big guns, howitzers, or mortars having a calibre greater than that of small arms, or infantry weapons. Rocket launchers are also commonly categorized as artillery, since rockets perform much the same functions as artillery projectiles, but the term artillery is more properly limited to large gun-type weapons using an exploding propellant charge to shoot a projectile along an unpowered trajectory. The dividing line between modern artillery and small arms is usually placed at a bore diameter, or calibre, of 0.60 inch or 15 mm. Weapons with a bore diameter greater than that are considered artillery, and those of smaller calibre are considered small arms. The term gun is reserved for a long-barreled, long-range artillery piece that fires its projectile in a relatively flat trajectory, while a howitzer has a shorter barrel and less range and shoots in a moderately arched trajectory. (Intermediate types capable of both functions are called gun-howitzers.) A mortar has a very short barrel, short range, and a hairpin trajectory owing to the high angle at which it is fired. Modern artillery originated in the second half of the 19th century. Before that period, cannons and mortars had not changed fundamentally since their introduction in the 14th century. Made of cast bronze or brass, cast iron, or wrought iron, they were classified according to the weight of the spherical balls they fired (e.g., 12-pounder, 24-pounder). Artillery was generally deployed as horse (for use with cavalry), field (for the support of infantry), and garrison (for coastal and fortress defense). Pieces were hauled on two-wheeled carriages by teams of horses, while wagons called limbers carried ammunition, tools, spare parts, and crewmen. The short ranges of these weaponsand of enemy musket firemeant that they were set up within sight of their targets. Upon firing, huge clouds of smoke were generated by the black-powder propellants, and the gun and carriage, having been thrown back by the recoil forces, had to be wrestled back into firing position. The bore was then swabbed out with a sponge to extinguish sparks, powder and shot were rammed from muzzle to breech, and the piece was fired again. By the end of the 19th century, hydropneumatic piston arrangements allowed a fired artillery piece to recoil atop the carriage and then return to approximately the same firing position as before. Hence the gun did not have to be relaid (re-aimed) between shots. By this means, round after round could be fired as fast as the gun could be reloaded. Quicker reloading was facilitated by new mechanisms allowing the insertion of the ammunition into the gun through the breech rather than through the muzzle. Gun barrels were now made of forged steel, and their bores were threaded with rifling grooves. These imparted a stabilizing spin to projectiles, which acquired an elongated shape and were propelled far beyond visual range by more powerful, smokeless, nitrocellulose-based gunpowders. Both powder and projectile were fixed in a metal cartridge case called a shell, which could be loaded quickly into the breech of a weapon. Since World War II, a common practice has been to distinguish between light, medium, and heavy artillery. Guns and howitzers up to 105 mm in calibre are called light, and those over 105 mm but not more than 155 mm are called medium. Light artillery supports ground troops in attack and defense, and medium artillery adds the function of bombarding enemy artillery as well as troop concentrations and facilities just behind the combat area. Heavy artillery, which is also intended to attack installations to the rear, is frequently mounted on lightly armoured, tracked or wheeled vehicles. These and the larger medium pieces are designed to deliver projectiles to a target area 100 m (330 feet) in diameter from as far away as 25 km (15 miles). To add to the devastation of rear areas, the United States and the Soviet Union designed nuclear-armed projectiles as small as 155 mm. Among the conventional types of shells fired by artillery are high-explosive rounds, which are used against infantry, light vehicles, and aircraft; armour-piercing rounds, which are used to penetrate tanks and other armoured vehicles, naval vessels, and reinforced structures; and various chemical rounds, which may be used to produce smoke or provide illumination on the battlefield. The coming of air power early in the 20th century led to the creation of the antiaircraft gun, a type of artillery that is also commonly divided into light (20 to 40 mm), medium (40 to 90 mm), and heavy (100 mm and more). Since World War II, all but the light antiaircraft guns have been rendered obsolete by tactical guided missiles, which have also caused the virtual disappearance of garrison artillery. The growing importance of heavy tanks spurred the development in World War II of recoilless rifles. These light artillery pieces, which measure up to 105 mm in calibre, eliminated recoil upon firing by allowing propellant gases to escape through a nozzle in the breech. They fire low-velocity explosive projectiles that, along with the recoilless principle itself, have been applied to shoulder-held infantry weapons since the war. Additional reading On artillery, a full history of gun design and development in the second half of the 19th century is presented in the official British handbook Treatise on Service Ordnance, 7th ed. (1908); an overview of artillery knowledge of that period, with useful historical background, is offered in E.W. Lloyd and A.G. Hadcock, Artillery: Its Progress and Present Position (1893). The design and development of the guns, carriages, ammunition, and tactics, with descriptions of current weapons, are covered in H.A. Bethell, Modern Guns and Gunnery, 1910: A Practical Manual for Officers of the Horse, Field, and Mountain Artillery, new ed. (1910), and Modern Artillery in the Field: A Description of the Artillery of the Field Army, and the Principles and Methods of Its Employment (1911). Thomas J. Hayes, Elements of Ordnance: A Textbook for Use of Cadets of the United States Military Academy (1938), is a later textbook covering the design and construction of guns, mountings, ammunition, and fire-control equipment in ample detail. Ian V. Hogg, A History of Artillery (1974), is a profusely illustrated history providing considerable technical detail on the development of arms from the 12th century to the present day. Jane's Armour and Artillery (annual) lists all current tanks and artillery weapons, with descriptions, specifications, and illustrations. Ian Vernon Hogg