The Imperial Heavy Siege Mortar (unofficial name) is a type of experimental self-propelled artillery fielded by the Imperial Army during the Invasion of Gallia. The Mortars made their first and only appearance in the Valkyria Chronicles 3 OVA, where Imperial forces uses them to bombard Gallian forces attempting to retake the Dillsburg Bridgehead.
Only three prototypes of the Heavy Mortar are known to exist, they first saw action during the defending of Dillsburg Bridgehead, oversaw by Commander Munchhausen of the Imperial Army. The first two, named Utto and Gurion, are deployed and positioned to fire, while the third unit, Esu, is under maintenance in its hangar.
The mortars were designed to fire special ragnite infused shells (indicated by the brilliant blue flash generated upon detonation), capable of creating shockwaves powerful enough to decimate entire forest patches and sent Gallian Light Tanks flying. The shells are extremely heavy and requires a specially designed crane to be loaded into the Mortars.
After the destruction of the mortars in the hands of Squad 422 and the subsequent fall of Dillsburg Bridgehead, the Imperial authority most likely deemed the mortars a failure and shut down its production. Which most likely explains why no other units of these mortars are encountered.
- The self-propelled mortars are based off the Karl-Gerät, otherwise known as Mörser-Karl. Particularly the earlier 600mm models. Like the mortars in the anime, all of the Karl-Geräte (excluding the 7th experimental model) are named.
- The running gear appears inspired more by the British TOG-1 superheavy tank.
- In the anime, the cranes carrying the mortars' shells is also in charge of loading the shells into the cannons. While the real-life Karl-Gerät requires the shells to be loaded manually, although a modified Panzer IV is required to transport and hoist the shells onto the Mörser.
- It's possible that Commander Munchhausen proposed the mortars to the Imperial authority personally, judging from how attached he is to his super weapons (calling them his "daughters").
- Judging from the Mortar's radiator positioning, it's likely that the vehicle has two engines, one positioned on each side to propel each set of treads.