Self - propelled artillery Self - propelled artillery ( also called mobile artillery or locomotive artillery ) is artillery equipped with an own propel system to move towards its target . Within the term are covered self - propelled gun s ( or howitzer s ) and rocket artillery . They are high mobility vehicles , usually based on caterpillar track carrying either a large howitzer or other field gun or alternatively a mortar or some form of rocket or missile launcher . They are usually used for long - range indirect bombardment support on the battlefield . In the past , self - propelled artillery has included direct - fire vehicles such as assault gun s and tank destroyer s . These have been heavily armoured vehicles , the former providing close fire - support for infantry and the latter acting as specialized anti - tank vehicles . Modern self - propelled artillery vehicles may superficially resemble tank s , but they are generally lightly armoured , too lightly to survive in direct - fire combat . However , they protect their crews against shrapnel and small arms and are therefore usually included as armoured fighting vehicle s . Many are equipped with machine gun s for defense against enemy infantry . The key advantage of self - propelled over towed artillery is that it can be brought into action much faster . Before the towed artillery can be used , it has to stop , unlimber and set up the guns . To move position , the guns must be limbered up again and brought — usually towed — to the new location . By comparison self - propelled artillery can stop at a chosen location and begin firing almost immediately , then quickly move on to a new position . This ability is very useful in a mobile conflict and particularly on the advance . Conversely , towed artillery was and remains cheaper to build and maintain . It is also lighter and can be taken to places that self - propelled guns cannot reach . Since the Vietnam war , heavy transport helicopter s have also been used for rapid artillery deployment . So despite the advantages of the self - propelled artillery , towed guns remain in the arsenal s of many modern armies . History . Precursors . During the Thirty Year ' s War early 17th century experiments were made with early types of horse artillery . Batteries towed light field guns where most or all of the crew rode horses into battle . The gunners were trained to quickly dismount , deploy the guns and provide instant fire support to cavalry , and act as a flexible reserve . The Russian army organized small units of horse artillery that were distributed among their cavalry formations in the early 18th century . While not forming large batteries and employing only lighter 3 - and 2 - pound guns , they were still effective and inflicted serious losses to Prussian units in the Seven Years ' War . This inspired Frederick the Great to organize the first regular horse artillery unit in 1759 . Other nations quickly realized the capability of the new arm and by the start of French Revolutionary Wars in 1790s Austria , Hannover , Portugal , Russia , France , Great Britain and Sweden had all formed regular units of horse artillery . The arm was employed throughout the Napoleonic Wars and remained in use throughout the entire 19th century and into the first half of the 20th century , when advances in weapons technology finally made it obsolete . World War I . The British Gun Carrier Mark I was the first example of a self - propelled gun , fielded in 1917 during World War I . It was based on the first tank , the British Mark I and carried a heavy field gun . The gun could either be fired from the vehicle , or removed and set up as normal . In effect the carrier replaced the use of a separate horse team or internal combustion engine powered artillery tractor , and allowed a new way for the gun to be used . Between the wars . The next major advance can be seen in the Birch gun developed by the British for their motorised warfare experimental brigade ( the Experimental Mechanized Force ) after the end of the War . This mounted a field gun , capable of both the usual artillery trajectories and high angle anti - aircraft fire , on a tank style chassis . It was designed and built as part of a general approach to warfare where all arms , infantry and artillery included , would be able to operate over the same terrain as tanks . The Red Army also experimented with truck - and tank - mounted artillery , but produced none in quantity . World War II . At the outbreak of World War II virtually all artillery was still being moved around by artillery tractors or horses . While the German Blitzkrieg doctrine called for combined - arms action , which required fire support for armoured units , during the invasion of Poland and France this was provided by the Luftwaffe using Stuka dive - bomber s effectively acting as artillery . Conventional towed howitzers followed . As the war progressed , most nations developed self - propelled artillery . Some early attempts were often no more than a field gun or anti - tank gun mounted on a truck - a technique known in the British Army as carrying " portee " . These were mobile , but lacked protection for the crew . The next step was to mount the guns on a tracked chassis ( often that of an obsolete or superseded tank ) and provide an armoured superstructure to protect the gun and its crew . Many of the early designs were improvised and the lessons learned led to better designs later in the war . For example , the first British design , " Bishop " , carried the 25 pdr gun - howitzer , but in a mounting that severely limited the gun ' s performance . It was replaced by the more effective Sexton . The Germans were particularly prolific with designs . They created many examples of lightly armored self - propelled anti - tank guns using captured French equipment ( example Marder I ) , their own obsolete light tank chassis ( Marder II ) , or ex - Czech chassis ( Marder III ) . These led to better protected tank destroyers , built on medium tank chassis such as the Jagdpanzer IV and Jagdpanther . Some designs were based on existing chassis ( such as the Brummbär ) , leftover chassis from cancelled programs ( Elefant and Sturer Emil ) ; others were converted from battle - damaged tanks ( Sturmtiger ) . The single most - produced armored fighting vehicle design for Germany in WW II , the Sturmgeschütz III assault gun , in 1936 - 37 pioneered the later casemate - style fully enclosed armor that would be used on almost all late - war German self - propelled artillery and tank destroyers . The Soviets experimented with truck - and tank - based self - propelled weapons , producing a few Komsomoletz tractor - mounted 57 - mm ZiS - 2 guns early in the war . By 1943 the series of " Samokhodnaya ustanovka " casemate - armored vehicles had started to appear at the front , starting with the SU - 85 , and by late 1944 the SU - 100 , which mounted powerful guns on modern chassis adopting the full - casemate enclosure of the crew compartment as the Germans had done with the StuG III . These had the advantage of being relatively cheap to build and mounting a larger gun compared to the conventional tank they were derived from , but at the expense of flexibility . Heavily armoured assault gun s , were designed to provide direct - fire support to infantry in the face of enemy defenses . Although often similar to tank destroyers , they carried larger caliber guns with weaker anti - armor performance but capable of firing powerful HE projectiles . The German StuH 42 and the Soviet ISU - 152 are good examples of this type of self - propelled artillery . All major nations developed self - propelled artillery which would be able to provide indirect support while keeping pace with advancing armoured formations . These were usually lightly armoured vehicles with open - topped hull , US M7 Priest , British Sexton ( 25 pdr ) and German Wespe and Hummel being typical examples . A different route was chosen by the Soviets , who didn ' t develop a specialized indirect fire vehicle , but following a tradition of dual - purpose towed artillery , built a series of versatile assault guns with indirect fire capabilities ( example ISU - 152 ) . But probably the most important breakthrough was the development of the famous Soviet Katyusha self - propelled multiple rocket launcher s which were unarmored trucks with a simple rocket rack on the back , a cheap and crushingly effective weapon . After the end of World War II , the assault gun fell from use with a general trend towards a single heavy gun - equipped vehicle , the main battle tank . Self - propelled indirect - fire artillery remained important and continued to develop alongside the general purpose field gun . Mortars . Many vehicles have used ancillary smoke mortars for local defense . Some vehicles are mortar carrier s and carry a mortar as a primary weapon . Vehicles with a mortar as a primary weapon that is mounted to be fired within the vehicle include the U . S . M4 half - track . Tanks such as the Israeli Makmat on the M4 Sherman tank chassis have also mounted mortars . The Russian army uses a " 2S4 Tyulpan " ( Tulipin ) self - propelled 240 mm heavy mortar . Patria Hägglunds , a joint venture between Finnish Patria and Swedish BAE Systems Hägglunds manufactures AMOS ( Advanced Mortar System ) which is a 120 mm automatic twin barrelled , breech loaded mortar turret . Howitzers and guns . Self - propelled artillery remains important in the equipment of many modern armies . It saw a significant role throughout the Cold War era conflicts and in the recent Gulf Wars . Modern SP artillery is highly computerized with the ability to self survey firing positions using systems such as GPS and inertial navigation system s . This , in conjunction with digital fire control / ballistic computers and digital communications , allows individual guns to disperse over a wide area and still deliver rounds on target simultaneously with the other guns in their battery . These capabilities also increase survivability manyfold as modern SP artillery can displace and avoid counterbattery fire much more quickly and effectively and if desired more frequently than previously possible . In conjunction with modern logistic systems ( where the SP gun ' s systems can track and report on ammunition consumption and levels ) with similar navigation systems and palletized load dropping / lifting capabilities mean that the rapid displacement can occur without significant disruption to actually firing missions as it is possible for the ammunition to keep up with the guns . A modern battery of six guns , each firing 43 kg projectiles with a burst firing speed of four rounds per minute , can deliver over a metric tonne of ordnance per minute for up to four minutes . This is an immense weight of fire which can be delivered with very high accuracy . One example of the increased firepower provided by modern mobile howitzers is the latest version , the " G6 - 52 " , of the 155 mm G6 howitzer . It can fire up to 6 rounds in quick succession which will land nearly simultaneously . This is achieved by firing the shells at different trajectories so that the first round has the longest flight time and the last round the shortest . The necessary rapid reloading is made possible by an automated ammunition feed system . Rockets and missiles . Rockets have greater ranges and carry much more complex " shells " than guns since there is less of a restriction on size ( calibre ) . The MLRS can be used to saturate a large area with sub - munitions .