Editing Indirect fire (section)

==History==
Indirect arrow fire by archers was commonly used by ancient armies. It was used during both battles and sieges.<ref>{{cite book |url=https://books.google.com/books?id=HscIwvtkq2UC&q=The+Ancient+World+Richard+A.+Gabriel+indirect+fire&pg=PA74 |title=The Ancient World |first=Richard A. |last=Gabriel |author-link=Richard A. Gabriel |page=74 |publisher=[[Greenwood Press]] |year=2007 |isbn=978-0-313-33348-4}}</ref>

For several centuries [[Coehorn mortar]]s were fired indirectly because their fixed elevation meant range was determined by the amount of propelling powder. It is also reasonable conjecture that if these mortars were used from inside fortifications their targets may have been invisible to them and therefore met the definition of indirect fire.{{original research inline|date=October 2012}}

It could also be argued{{according to whom|date=October 2012}} that [[Niccolò Fontana Tartaglia|Niccolò Tartaglia]]'s invention of the ''gunner's quadrant'' (see [[Inclinometer|clinometer]]) in the 16th century introduced indirect fire guns because it enabled gunlaying by instrument instead of line of sight.<ref>''Artillery: Its Origin, Heyday and Decline'', Brigadier O. F. G. Hogg, 1970, C. Hurst and Company</ref> This instrument was basically a carpenter's [[set square]] with a graduated arc and [[plumb-bob]] placed in the muzzle to measure an elevation. There are suggestions,<ref name="ReferenceA">''The History of the Royal Artillery from the Indian Mutiny to the Great War, Vol II, 1899–1914'', Major General Sir John Headlam, 1934</ref> based on an account in ''Livre de Canonerie'' published in 1561 and reproduced in ''Revue d'Artillerie'' of March 1908, that indirect fire was used by the Burgundians in the 16th century. The Russians seem to have used something similar at [[Battle of Kay|Paltzig]] in 1759 where they fired over trees, and their instructions of the time indicate this was a normal practice.<ref>''"Red God of War" Soviet Artillery and Rocket Forces'', Chris Bellamy, 1986</ref> These methods probably involved an [[aiming point]] positioned in line with the target.{{citation needed|date=October 2012}} The earliest example of indirect fire adjusted by an observer seems to be during the defence of [[Hougoumont]] in the [[Battle of Waterloo]] where a battery of the [[Royal Horse Artillery]] fired an indirect [[Shrapnel shell|Shrapnel]] barrage against advancing French troops using corrections given by the commander of an adjacent battery with a direct line of sight.<ref>''Against All Odds!: Dramatic Last Stand Actions''. Perret, Brian. Cassell 2000. {{ISBN|978-0-304-35456-6}}: discussed during the account of the Hougoumont action.</ref>

Modern indirect fire dates from the late 19th century. In 1882 a Russian, Lt Col K. G. Guk, published ''Field Artillery Fire from Covered Positions'' that described a better method of indirect laying (instead of aiming points in line with the target). In essence, this was the geometry of using angles to aiming points that could be in any direction relative to the target. The problem was the lack of an azimuth instrument to enable it; [[clinometer]]s for elevation already existed. The Germans solved this problem by inventing the lining-plane in about 1890. This was a gun-mounted rotatable open sight, mounted in alignment with the bore, and able to measure large angles from it. Similar designs, usually able to measure angles in a full circle, were widely adopted over the following decade. By the early 1900s the open sight was sometimes replaced by a [[telescope]] and the term [[goniometer]] had replaced "lining-plane" in English.

The first incontrovertible, documented use of indirect fire in war using Guk's methods, albeit without lining-plane sights, was on 26 October 1899 by British gunners during the [[Second Boer War]].<ref name="Evolution">{{Cite book|url=https://books.google.com/books?id=5dmYQPNfGFsC&pg=PA30|title=The Evolution of Indirect Fire|author=Frank W. Sweet|pages=28–33|isbn=0-939479-20-6|publisher=Backintyme|year=2000}}</ref> Although both sides demonstrated early on in the conflict that they could use the technique effectively, in many subsequent battles, British commanders nonetheless ordered artillery to be "less timid" and to move forward to address troops' concerns about their guns abandoning them.<ref name="Evolution"/> The British used improvised gun arcs with howitzers;<ref name="ReferenceA"/> the sighting arrangements used by the Boers with their German and French guns is unclear.

The early goniometric devices suffered from the problem that the layer (gun aimer) had to move around to look through the sight. This was very unsatisfactory if the aiming point was not to the front, particularly on larger guns. The solution was a periscopic panoramic sight, with the eyepiece to the rear and the rotatable top of the sight above the height of the layer's head. The German Goertz 1906 design was selected by both the British and the Russians. The British adopted the name "Dial Sight" for this instrument; the US used "Panoramic Telescope"; the Russia used "[[:ru:Панорама Герца|Goertz panorama]]".

Elevations were measured by a [[Inclinometer|clinometer]], a device using a [[spirit level]] to measure a vertical angle from the horizontal plane. These could be separate instruments placed on a surface parallel to the axis of the bore or physically integrated into some form of sight mount. Some guns had clinometers graduated in distances instead of angles. Clinometers had several other names including "gunner's level", "range scale", "elevation drum" and "gunner’s quadrant" and several different configurations. Those graduated in ranges were specific to a type of gun.

These arrangements lasted for most of the 20th century until robust, reliable and cost-effectively accurate [[gyroscope]]s provided a means of pointing gun or launcher in any required azimuth and elevation, thereby enabling indirect fire without using external aiming points. These devices use gyros in all three axes to determine current elevation, azimuth and trunnion tilt.