The Anti-Tank Cannon is a specific type of Fixed Weapon seen throughout the Valkyria Chronicles series: like all such weapons, it is handled as essentially a very weak vehicle. These weapons cannot move and have a fixed 90 degree fire arc to their front. They were first seen in the series in Valkyria Chronicles' Chapter 05: The Kloden Wildwood.
Anti-tank guns in this game are mainly objectives for the player to take out before the Imperial turn starts in order to avoid heavy damage: when they are first encountered in the Kloden Wildwood, they are strong enough that just two shots will be enough to destroy the Edelweiss, and their B-rated accuracy means they are far more likely to hit than Welkin's tank is without a large number of accuracy upgrades.Heavy anti-tank cannons are encountered later in the game and deal increased damage to personnel and tanks, on top of having slightly improved health and defense. Visually, they have longer barrels and are redder in color compared to standard AT cannons.
The one saving grace of these cannons is that they are unable to intercept your units in Valkyria Chronicles, for their high damage, accuracy, and range would otherwise render many areas completely inaccessible for fear of their fire (giving them the ability to intercept is part of the reason why the Gallian Crossfire mod by Busards is so difficult).
The weapon itself is implemented as a tough "body" with the soldier manning it as the critical hit location: he is not actually an infantryman, just being an extension of the gun, and disappears when it is destroyed.
Valkyria Chronicles 4
Anti-Tank Cannons become significantly more dangerous in VC4: while they have to deal with decreased vs Armor and accuracy stats, alongside an ammunition limit, they compensate for it by being able to fire an infinite number of rounds of weaker interception fire at any tanks within their range and field of view. They will not try to intercept infantry.
- The addition of interception fire to Anti-Tank Cannons in VC4 may well have been inspired by a 2015 mod for the PC version of VC1 called "Gallian Crossfire." This also made several other changes later present in VC4.