|While we were putting all our faith in the power of the Titans and pursuing our colonial policies, other countries who could never depend on the Titans developed weapons to oppose them. Our situation today is the result.|
|— Commander Theo Magath deduces the origin of anti-Titan artillery|
Anti-Titan artillery was created for the purpose of destroying Titans of all varieties with great efficiency. It fires 100mm shells, and the armor-piercing type of which has enough firepower to kill even the Nine Titans, such as the Armored or Beast Titan, with a single shot. Besides killing Titans, the gun was also used in normal bombardment missions in which it fired fragmentation shells.
During the battle of Fort Slava, four anti-Titan artillery guns are mounted on an armored train surrounding the fortress, allowing for great mobility on the battlefield. However, the guns were more commonly mounted in field gun carriages. At least 28 guns in the latter configuration were deployed on the fort's wall, forming the main barrage ring of the Allies' defender.
Even when fitted on a field gun mount, the anti-Titan gun was very maneuverable, being able to turn about quickly by a crew of four to face threats behind it. For example, the guns managed to score a few hits against a fast-moving Armored Titan, and were able to react effectively against the mindless Titans landed inside the fort. However, it was not without its weakness. The gunners still have to land an accurate shot on the approximate area of the nape of the neck for an effective kill. The gun also has a limited degree of depression, as the field guns on the fort were unable to fire upon the Cart and Jaw Titans who were outside the wall, but the standing Titans inside the fort were within range.
Although the gun was said to be a new weapon, its sizable number and different variants may suggest that the Allies mass-produced the gun in such quantity that it became the Allies' standard field artillery piece by the time of the battle.
Anti-Titan artillery makes its debut in the Marley Mid-East War during the battle of Fort Slava, where it is mounted on an armored train traveling along rails surrounding the perimeter of the fortress. The presence of the weapon prevents the use of the power of the Titans possessed by Marley, drastically reducing Marley's ground-based power. However, the armored train and its anti-Titan gun turrets are both rendered unusable when Warrior cadet Gabi Braun destroys its lead car with a bundle of grenades, allowing for Porco Galliard to make use of his Jaw Titan power and directly attack the Mid-East Allied Forces' defenses.
After Titans are airdropped into the fort, the field guns remaining on the fort attempt to put them down, but are stopped by the Armored Titan. Although the Armored Titan succeeds in destroying all the guns by sweeping them apart with a watch tower which it uses as a club, the damage it sustains alert him of the unprecedented lethality of the new weapon.
After the war ended, the Marleyan military was able to acquire the guns for their own usage. While inexperienced, they were able to use them to hinder the Attack Titan's movements against the War Hammer Titan before the guns became targets for the Survey Corps and their re-purposed Thunder Spears.
During Revenge for Liberio, as Zeke and Eren try to make their way to the other, Eren notices out of the corner of his eye that a tearful Gabi has picked up the deceased Colt's anti-Titan rifle. Before anyone can react, she shoots a round into Eren's neck, decapitating him.
Later on in the battle, the Blouse family and Niccolo flee from one of the newly created Titans and Kaya accidentally falls down a set of stairs. As the Titan lunges for her, it is shot through the mouth by Gabi, causing it to fall. She jumps in front of Kaya and jams her rifle down the Titan's throat so she can blow out the nape. An Eldian soldier sees them and demands to know if Gabi was the one who killed that Titan and if she is the kid from Marley. Kaya covers for her, saying that Gabi is a part of her family and Niccolo claims that he used the gun since he was trained as a former Marleyan soldier.