Self-propelled guns (also known as artillery,SPGs, arty) are fragile armored vehicles which provide indirect fire support from a long distance. They are represented by a green or red square on the mini-map and over their respective target marker.
Artillery are the most unique class of armored vehicles in the game, sharing very few characteristics with the other four classes. Artillery's most distinguishing feature is its ability to aim and shoot over terrain and other obstacles. Unlike the other four classes, SPGs do not get a "sniper" mode. Instead, by pressing left shift, the player enters a birds-eye view which allows them to look at a limited area of any chosen part of the map. Using this view artillery can aim at enemy targets over terrain and structures (depending on the size of the structure, the trajectory of the shell, and the range of the artillery's gun).
Artillery generally have the most powerful, highest caliber guns for their tier. Unlike most tanks and tank destroyers, artillery fire high-explosive (HE) shells as their primary form of ammunition. This type of shell explodes on impact and does not need to penetrate a vehicle's armor to do damage. The explosion of a large HE shell can also deal splash damage to nearby targets (both allies and enemies) who aren't hit directly. These advantages do come at a price, however. Artillery guns usually have long reload times, poor accuracy, and are very slow to aim. Artillery cannot quickly change targets or follow fast-moving enemies without a considerable accuracy penalty. Like many tank destroyers, most artillery have limited-traverse guns mounted in their hull (although a few do get slow-turning turrets). Turning beyond a hull-mounted gun's maximum traverse range requires turning the vehicle's hull, which results in camo and accuracy penalties. In addition, artillery are also the most fragile class of vehicles in the game. Artillery can only withstand a few hits from even the smallest of enemy guns, and their high aim times and long reload times make it difficult for them to defend themselves against close-range attackers.
Artillery are glass cannons; they are best played far behind the front lines attacking targets that allied tanks may have difficulty damaging (usually heavy tanks, snipers, and opportunity targets). It is important for artillery to position themselves in an area where they can make a meaningful contribution to the game with their attacks, but are still stay safe from enemy scouts and spotters. Artillery are almost purely a support class, and rely heavily on allied vehicles to spot and distract targets for them. It is important for artillery players to keep track of the map and re-position to safer areas when necessary. If re-positioning is not possible, an artillery can attempt to defend itself by using ambush tactics to surprise-attack enemies at point-blank range.
Variety and Role
While all artillery must play as behind-the-lines vehicles giving support fire, there is some variety within the class. Some, such as the S-51 are capable of doing huge amounts of damage in one shot, but have extremely long reload times, and require special patience not to waste the few shots they can take. Others, such a the FV304 and many French artillery, fire very quickly but have little to no splash radius and do very little damage. Beyond this, there are a whole host of other factors which differentiate artillery, such as shell velocity, shell trajectory, and mobility, all of which contribute to the different strengths and weaknesses of each vehicle.
Since patch 9.18, the role of artillery has changed. The alpha damage has been reduced, in exchange for better accuracy and the ability to "stun" enemy tanks, temporarily reducing their effectiveness.