An assault gun is an armoured fighting vehicle similar to a tank, but typically does not have a traversable turret, and may have an open roof. The removal of the turret allows for a much larger gun to be carried on a smaller chassis. They are very similar to an anti-tank vehicle, but mount a gun of much larger bore and lower velocity, typically some form of howitzer. They are not intended to fight other AFV's, but instead directly support infantry during assaults on prepared positions. Assault guns were primarily built due to their low cost in getting a large gun into the field. A similarly armed "full tank" would be much bigger and more expensive due to the turret.

History

Assault guns saw their main use during World War II, in the hands of the Germans and Soviets. The Soviets deployed a modified version of the KV-1 heavy tank with a cut-off 152mm howitzer as the KV-2. Uncommonly the KV-2 mounted the gun in a turret, which had to be rather outsized and made it an easy target. On the other hand the gun was quite powerful and also proved to be quite useful against German armor.

German assault guns were mounted on much lighter chassis, starting with the Pz I and II before developing into the fairly useful Pz III based Sturmgeschütz III. Although the StuG's 75mm gun was an improvement over the Pz III's 50mm anti-tank gun, it was nowhere near as useful as the larger Soviet versions. More annoying for the users were that the relativily thin armor of the Pz III chassis meant that the gun was not able to travel in close with the infantry once man-portable anti-tank weapons started to proliferate. In order to address these problems the 150mm armed Sturmpanzer IV was developed, but suffered from being overweight. This was then planned to be replaced by the even larger Sturmpanther , and the utterly ridiculous Sturmtiger.

Postwar use

In the post-WWII era a second use was envisioned for the assault gun, as a light-weight air-deployable direct fire weapon for use with airborne troops. Current weapons were either based on jeeps or small tracked vehicles and the airborne troops thus always fought at a distinct disadvantage in terms of heavy weapons.

The US was the first to build an assault gun in this category, the 152mm armed M551 Sheridan. The Sheridan's gun was a low-velocity weapon suitable in the assault role, but with the addition of the Shillelagh missile could double in the anti-tank role as well. The Sheridan was generally considered a failure however, and largely detested by its crews.

An attempt to address the Sheridan's problems and provide the airborne divisions with a modern weapon system developed into the M8 Armored Gun System (or AGS). However the AGS was continually stung with budget cuts and program changes, and was never produced. Instead a wheeled vehicle based on the standard LAV III wheeled chassis is being deployed with the 105mm gun as the Stryker.