Field artillery Field artillery is a category of mobile artillery used to support armies in the field . These weapon s are specialized for mobility , tactical proficiency , long range , short range and extremely long range target engagement . Until the early 20th century , field artillery were also known as foot artillery , for while the guns were pulled by beasts of burden ( often horses ) , the gun crew s would usually march on foot , thus providing fire support mainly to the infantry . This was in contrast to horse artillery , whose emphasis on speed while supporting cavalry units necessitated lighter guns and crews riding on horseback . Whereas horse artillery has been superseded by self - propelled artillery , field artillery has survived to this day both in name and mission , albeit with motor vehicles towing the guns , carrying the crews and transporting the ammunition . Modern artillery has also advanced to rapidly deployable wheeled and tracked vehicles and precision delivered munitions capable of striking targets at ranges between 15 and 300 kilometers . History . Early modern era . Early artillery was unsuited to the battlefield , as the extremely massive pieces could not be moved except in areas that were already controlled by the combatant . Thus , their role was limited to such functions as breaking siege s . Following the beginning of the gunpowder era , the first field artillery came into being as metallurgy allowed thinner cannon barrels to withstand the explosive forces without bursting . However , there was still a serious risk of the constant changes of the battlefield conspiring to leave behind slow - moving artillery units - either on the advance , or more dangerously , in retreat . Artillery units were particularly vulnerable to assault by light cavalry , which were frequently used in this role . Only with a number of further inventions ( such as the limber , hitched to the trail of a wheeled artillery piece equipped with trunnion s ) , did the concept of field artillery really take off . One of the earliest documented uses of field artillery is found in the 14th century Ming Dynasty treatise " Huolongjing " . The text describes a Chinese cannon called a " thousand ball thunder cannon , " manufactured of bronze and fastened with wheels . The book also describes another mobile form of artillery called a " barbarian attacking cannon " consisting of a cannon attached to a two - wheel carriage . 20th century . Before World War I , field artillery batteries generally fired directly at visible targets measured in distances of meters and yards . Today , modern field batteries measure targets in kilometers and miles and often do not directly engage the enemy with observed direct fire . The hundredfold increase in the range of artillery guns in the 20th century has been the result of development of rifled cannon s , improvements in propellants , better communications between observer and gunner and technical improvements in gun nery computational abilities . Most field artillery situations require indirect fire due to weather , terrain , night - time conditions , distance or other obstacles . These gunners can also rely upon a trained artillery observer , also called a forward observer who sees the target , relays the coordinates of the target to their fire direction center which , in turn translates those coordinates into : a left - right aiming direction ; an elevation angle ; a calculated number of bags of propellant and finally a fuze with a determined waiting time before exploding , ( if necessary ) to be set , which is then mated to the artillery projectile now ready to be fired . Field artillery team . Modern field artillery ( i . e . post - World War I ) has three distinct sections : All batteries have a Fire Support Man ( Forward Observer ) , Fire Direction Control ( FDC ) , and Cannoners ( Gunner ) . The FOs are forward with the infantry ( in support role ) where they can see the targets and Call For Fire ( CFF ) upon them . They call the FDC on the radio and transmit a request for fire in the format of CFF . The FDC calculates the CFF and send a deflection and elevation to the gun line . The gun line cranks the specified elevation and deflection on the howitzers , punch the artillery shell followed by the bag ( powder ) . Depending on the CFF , the gunline will fire the round when they are ready or when the FO calls and tells them to fire . The FO spots the round and sends a correction back to the FDC and the process starts all over again until its done . The batteries are many kilometres behind the FLOT ( Forward Line of Troops ) . They plan a location where they can be Fire Capability for some certain amount of time and do multiple fire missions before needing to displace . In normal operations the FOs locate targets and transmits the CFF to the FDCs . They can also calculate " defensive fire " tasks . These are pre ‑ planned missions , typically just in front of or upon one ' s own positions , designed with the intention of either suppressing potential attacks ( where fire is dropped just in front of a friendly position ) , or in dropping fire on a recently abandoned or overrun position to prevent the enemy from consolidating there . Because the calculations have already been done , the fire can be called down very quickly when it is needed . Reconnaissance and Advance Party . The Advance Party consists of the Battery Commander , his Driver , First Sergeant , Gunnery Sergeant , FDC Guide , Gun Guides , and Communications Representatives . Initially the Party looks to find suitable positions for an artillery unit to perform fire missions from . Then they perform what is known as route reconnaissance . The primary purpose of this reconnaissance is to determine the suitability of the route of the units movement . Items to be analyzed include possible alternate routes , cover , concealment , location of obstacles , likely ambush sites , contaminated areas , route marking requirements , and the time and distance required to traverse the route . Several factors are taken into consideration . Once a location is determined and having arrived at the new position the advance party conducts a security sweep and prepares the position for occupation . The purpose of the advance party security with METT - T and the absence of enemy troops , mines , booby traps , NBC hazards , and so on . If these threats or conditions are present in the proposed position area , the advance party breaks contact with any enemy forces or marks minefield and hazards and moves on to find another position area . The battery commander can coordinate for additional assets , or augment the advance party with internal assets , to provide the additional ability to clear areas of small enemy forces , obstacles , and minefields . Natural cover must be used to the maximum . Security is continuous throughout advance party operations . Once a location is determined to be safe the advance party prepares the position for eventual howitzer emplacement . This consists of several procedures such as escorting each howitzer to its prepared position , setting up communications , providing the unit with its initial azimuth of fire , and providing each gun with an initial deflection . This entire process is covered in U . S . Army Field Manual 6 - 50 Chapter 2 . Forward Observer . Because artillery is an indirect fire weapon , the forward observer must take up a position where he can observe the target using tools such as binoculars and laser rangefinders and call back fire missions on his radio or telephone . The FO usually sits on the ground in cover , from which he can see the enemy . However , he may also be airborne — this was one of the very first uses of aircraft in World War I . He must take great care not to be observed by the enemy , especially if in a static position . Discovery of an FO does not only jeopardize his personal safety ; it also hampers the ability of the battery to lay fire . Using a standardized format , the FO sends map references and bearing to target , a brief target description , a recommended munition to use , and any special instructions such as " danger close " ( the warning that friendly troops are within 600 meters of the target when using artillery , requiring extra precision from the guns ) . The FO and the battery iteratively " walk " the fire onto the target . The FDC signals the FO that they have fired and the FO knows to observe fall of shot . He then signals corrections . These are normally of the form of left / right of the bearing line and distance along it , for example " right 50 add 100 " ( distance in meters ) . When the fire is good enough the FO signals " target on , fire for effect " . If the mission requires a walking barrage he may continue sending correction orders . The FO may be called upon to direct fire for close air support and / or naval artillery in addition to field artillery based howitzer and Infantry based mortar units . The U . S . Army Field Manual describing the duties and responsibilities is FM 6 ‑ 30 , " Tactics , Techniques , and Procedures for Observed Fire " . Fire direction center . Typically , there is one FDC for a battery of six guns , in a light division . In a typical heavy division configuration , there exist two FDC elements capable of operating two four - gun sections , also known as a split battery . The FDC computes firing data — fire direction — for the guns . The process consists of determining the precise target location based on the observer ' s location if needed , then computing range and direction to the target from the guns ' location . These data can be computed manually , using special protractors and slide rules with precomputed firing data . Corrections can be added for conditions such as a difference between target and howitzer altitudes , propellant temperature , atmospheric conditions , and even the curvature and rotation of the Earth . In most cases , some corrections are omitted , sacrificing accuracy for speed . In recent decades , FDCs have become computerized , allowing for much faster and more accurate computation of firing data . The FDC at the battalion level is responsible for recording friendly and enemy positions , tracking available battery munitions , and determining the optimal response for engaging a target identified by the FO . Command post . In most Artillery Batteries the Command Post ( CP ) controls the firing of the guns . It is usually located at the battery center so as to be able to communicate easily with the guns . The CP should be well camouflaged , but the CPO ( Command Post Officer ) should be able to see all the guns with ease . Gun markers are sometimes placed in front of the CP to remind the CPO which gun is in which position . The CPO is assisted by two " Acks " — i . e . , assistants — who operate the fire data computers . The GPO ( Gun Position Officer ) and CPO work at the plotter to ensure that the data calculated by the Acks is accurate and safe . The CP signaller is contact with the OP , or Observation Post , where the Forward Observer Officer ( FOO ) , works with the OP team to identify targets and call - back fire data . In recent years headset radios have become common for communication between the CPO and gun detachment commanders . Guns . The final piece of the puzzle is the gun line itself . The FDC will transmit a warning order to the guns , followed by orders specifying the type of ammunition and fuze setting , bearing , elevation , and the method of adjustment or orders for fire for effect ( FFE ) . Elevation ( vertical direction ) and bearing orders are specified in mils , and any special instructions , such as to wait for the observer ' s command to fire relayed through the FDC . The crews load the howitzers and traverse and elevate the barrel to the required point , using either hand cranks ( usually on towed guns ) or hydraulics ( on self - propelled models ) . Counter battery . Fire aimed at disabling or destroying enemy guns is known as counter - battery fire . Removing the threat posed by enemy artillery is an important objective on the battlefield . Most of the time enemy batteries are too far away for the infantry to engage , so it falls to artillery to do this job . The battery uses a variety of techniques to calculate the position of the enemy battery , then can lay fire upon it . If possible , a FO can access a position to call fire on enemy guns directly ; either on the ground or in the air , or a battery can be located using counter - battery radar , which can be used to observe the fall of enemy shells and thus calculate their trajectory . A correctly calculated trajectory will reveal the location from which the shell was fired , which information can then be passed on to a friendly battery command post as a fire mission . Defenses against counter - battery fire . To defend against counter battery fire there are two points of attack : either remove the enemy ' s ability to observe or make his observations irrelevant / obsolete . To remove the ability to observe one must attack the observation assets . Because most counter - battery radar is active , the location can be determined electronically from listening to the beams . If one suspects one ' s position is being observed by a covert FO then a mission , either artillery or infantry , will be raised to deal with this threat . Alternatively one can choose to make their observations obsolete by repeatedly moving the guns : hence self - propelled gun s . Ordinary towed guns can take a while to emplace and re - limber and are not armoured , so they are vulnerable to counter battery fire and take a while to engage when at a new location . Self - propelled guns do not suffer from these restrictions . They can drive up , drop their trails , fire and move on . Because of their armour they are less vulnerable to counter - battery fire . However , this armor is light by comparison to that of a tank , so it only protects from light fire ( e . g . , machine gun s ) and shrapnel . Another disadvantage of self - propelled guns is that they tend to be equipped with lighter , less accurate guns . Depending on the nature of the battle being fought , either or both of these drawbacks could prove a severe restriction . However , this is not necessarily true of modern self - propelled guns such as the German PzH 2000 . This has a 155 mm main armament that can with assisted firing charges reach 60 km . , has an average speed of 35 mph , and has a fully computerised fire - control system that enables it to fire - move - fire before the enemy can pin it down for counter - battery fire . It has a rate of fire 10 rounds per minute . Parent battalion and U . S . Army brigade / USMC regimental FDCs . FDCs also exist in the next higher parent battalion that " owns " two to four artillery batteries . Once again , an FDC exists at the U . S . Army brigade or USMC regimental level that " owns " the battalions . These higher level FDCs monitor the fire missions of their subordinate units and will coordinate the use of multiple batteries or even multiple battalions in what is called a battalion or brigade / regimental mission . In training and wartime exercises , as many as 72 guns from 3 battalions may all be coordinated to put " steel on the target " in what is called a " brigade / regimental time on target " or brigade / regimental TOT for short . The rule is " silence is consent " , meaning that if the lower unit does not hear a " cancel the mission " ( don ' t shoot ) or even a " check firing " ( cease firing ) order from the higher monitoring unit , then the mission goes on . Higher level units monitor their subordinate unit ' s missions both for active as well as passive purposes . Higher - level units may also get involved to coordinate artillery fire across fire support coordination boundaries ( often parallel lines on maps ) where one unit can not fire into without permission from higher and / or adjacent units that " own " the territory .