The Mole Mortar is an inverted standard mortar and infantry support weapon that fires a burrowing sub-surface missile, known as a tunnel-torpedo, into the ground. The tunnel-torpedo then burrows towards its target, bypassing all surface obstructions until it suddenly erupts from the ground and explodes beneath its designated target. The tunnel-torpedo is a self-guided munition and is able to track its target through metres of solid rock using advanced archeotech now lost to the Imperium. The Mole Mortar was invented by the Engineers Guild of the Squats and was later adopted for use by the Imperial Guard once the Squats rejoined the Imperium of Man and began to serve in several Guard regiments. The Mole Mortar was used by the Guard to penetrate certain fortifications or emplacements that had proven too strong for conventional infantry weapons to damage. As a result of its unique form of attack, the Mole Mortar could penetrate its target from below where it lacked all structured defences. The Mole Mortar was also used by the Adeptus Mechanicus' regiments of cybernetic Skitarii soldiers, who used it as a close support weapon. The Skitarii would unleash the Mole Mortar's tunnel-torpedoes on the most heavily armoured enemy units from below and then exploit the confusion in the enemy lines after the Squat weapon had done its deadly work. With the genocide of most of the Squat race following the Tyranid assault upon the Squat homeworlds in the late 41st Millennium, the Mole Mortar has become a weapon now rarely deployed in the Imperial armed forces' arsenal.
- Armies of the Imperium (2nd Edition), "Imperial Wargear," pg. 42
- Ork and Squat Warlords (2nd Edition), pg. 61
- Space Marine Battles (2nd Edition), pg. 7
- Warhammer 40,000: Battle Manual (2nd Edition), pg. 74
- Warhammer 40,000: Wargear (2nd Edition), pg. 52
- White Dwarf 136 (UK) (Ad Insert), pg. 75