Editing Rocket-propelled grenade (section)

===Predecessor weapons===
{{Main|Anti-tank weapons}}
The static nature of [[trench warfare]] in [[World War I]] encouraged the use of shielded defenses, even including personal armor, that were impenetrable by standard rifle ammunition. This led to some isolated experiments with higher caliber rifles, similar to [[elephant gun]]s, using [[armor-piercing ammunition]]. The first [[tank]]s, the British [[Mark I tank|Mark I]], could be penetrated by these weapons under the right conditions. [[Mark IV tank]]s, however, had slightly thicker armor. In response, the Germans rushed to create an upgraded version of these early anti-armor rifles, the [[Tankgewehr M1918]], the first [[anti-tank rifle]]. In the [[inter-war years]], tank armor continued to increase overall, to the point that anti-tank rifles could no longer be effective against anything but [[light tank]]s; any rifle made powerful enough for heavier tanks would exceed the ability of a soldier to carry and fire the weapon.

Even with the first tanks, artillery officers often used [[field gun]]s depressed to fire directly at armored targets. However, this practice expended much valuable ammunition and was of increasingly limited effectiveness as tank armor became thicker.<ref name=Norris/> This led to the concept of [[anti-tank guns]], a form of [[artillery]] specifically designed to destroy [[armored fighting vehicles]], normally from static defensive positions (that is, immobile during a battle).<ref>Oxford Advanced Lerner's Dictionary of Current English, New Edition, Cornelsen & Oxford, A S Hornby, 5th edition, p. 42.</ref><ref name=Norris>{{cite book|last=Norris|first=John|title=Brassey's Modern Military Equipment: Anti-tank weapons|date=1997|pages=7–21|publisher=Brasseys UK Ltd|location=London|isbn=978-1857531770}}</ref>

The first dedicated [[anti-tank artillery]] began appearing in the 1920s, and by [[World War II]] was a common appearance in most armies.<ref name=Gander>{{cite book |last1=Gander |first1=Terry |last2=Chamberlain |first2=Peter |title=World War II Fact Files: Anti-tank Weapons |date=1974 |pages=1–6 |publisher=Arco Publishing Company, Incorporated |location=New York |isbn=978-0668036078}}</ref> In order to penetrate armor they fired specialized ammunition from proportionally longer barrels to achieve a higher muzzle velocity than field guns.<ref>Militärisches Studienglosar Englisch Teil II/ Teil III, Deutsch – Englisch, Abkürzung Begriff, Bundessprachenamt (Stand Januar 2001), p. 283, anti-tank ammunition.</ref> Most anti-tank guns were developed in the 1930s as improvements in tanks were noted,<ref name=Rottman>{{cite book |last=Rottman |first=Gordon |title=World War II Infantry Anti-Tank Tactics |date=2005 |pages=15–17 |publisher=Osprey Publishing |location=Oxford |isbn=978-1841768427}}</ref> and nearly every major arms manufacturer produced one type or another.<ref name=Gander/>

Anti-tank guns deployed during World War II were manned by specialist infantry rather than artillery crews, and issued to infantry units accordingly.<ref name=Rottman/> The anti-tank guns of the 1930s were of small caliber; nearly all major armies possessing them used {{convert|37|mm|abbr=on}} ammunition, except for the [[British Army]], which had developed the {{convert|40|mm|abbr=on}} [[Ordnance QF 2-pounder]].<ref name=Norris/> As World War II progressed, the appearance of heavier tanks rendered these weapons obsolete and anti-tank guns likewise began firing larger calibre and more effective armor-piercing shells.<ref name=Gander/> Although a number of large caliber guns were developed during the war that were capable of knocking out the most heavily armored tanks, they proved slow to set up and difficult to conceal.<ref name=Gander/> The latter generation of low-recoil anti-tank weapons, which allowed projectiles the size of an artillery shell to be fired from a man's shoulder, was considered a far more viable option for arming infantrymen.<ref name=Rottman/>