A Heavy Mortar used by the Death Korps of Krieg during the Siege of Vraks

The Heavy Mortar Cannon, or simply the Heavy Mortar, is a field artillery piece that has been part of the Imperium’s arsenal since the earliest years of the Great Crusade, and quite likely even the Unification War on holy Terra itself. In this distant past, the Heavy Mortars was used by both the troops of the Imperial Army and the Legiones Astartes, espacially those specialized in siegecraft such as the Iron Warriors. Today however, the Heavy Mortar is only used by the Imperial Guard's siege companies, having been replaced by more sophisticated weapons. The weapon is a larger version of the standard mortar weapon used by most Imperial Guard forces. It is also the same weapon used on the Griffon self-propelled mortar tank. The weapon is classified as field artillery, which, unlike heavy artillery, is used close to the front lines in direct support of the infantry and vehicles that are already in combat rather than being fired from well behind the lines, usually in preparation for an assault. The Heavy Mortar's primary advantages include its wide range of ammunition types, a high rate of fire, and its great simplicity to construct and maintain. The weapon is light enough to be easily towed behind a Centaur utility vehicle, and can be set-up or torn down quickly and moved either to safety or to get closer to the enemy as the Imperial lines advance.

The Heavy Mortar is used to directly support the Imperial Guard's front-line forces by dropping powerful and accurate shells onto the enemy. The weapon has several different types of shells it can use, each with a different and specific purpose. The weapon is loaded one shell at a time, and can only fire one shell at a time, unlike the Imperial Quad Cannon, which fires four shells at a time, but the Heavy Mortar is preferred by most Imperial Guard siege units due to the diversity of its ammunition. The Heavy Mortar can be towed quickly across the battlefield by a Centaur or a Trojan. During combat the Centaur can provide cover to the gunner crew, and the Trojan can be seen travelling back and forth from the ammunition stockpile to keep the crew from running out of shells to fire.

While Heavy Mortars were once used by many different Imperial Guard regiments, their use has declined in recent years because many Imperial officers feel that the weapon lacks both the heavier firepower and longer reach of true field artillery, limiting its use to box-barrages or tactical counter-battery fire. Heavy Mortars that must be towed into combat are now seen as too slow to keep up with advancing mechanised units and self-propelled artillery. Many have now been relegated to the Planetary Defence Forces and Imperial Guard siege regiments.

As one of the lightest types of artillery available to the Imperial Guard though, many still see it as an ideal compromise between mobility, firepower and ease of use. In this case they are an excellent close support weapons for engaging enemy infantry and light vehicles, freeing the heavier artillery for use against more appropriate targets. Its versatility also allows it to fulfill a variety of other roles, from launching illumination shells during night battles or laying down a smoke screen before an infantry attack.



A Centaur towing a Heavy Mortar Cannon

  • High Explosive - High Explosive Rounds are the standard shells used by the Heavy Mortar Cannon. These shells are more than capable of destroying infantry units and even vehicles through their sheer explosive force.
  • Fragmentation - Fragmentation Rounds are timed charge shells that explode before hitting the ground and shower the area with shrapnel. These shells are employed against large numbers of closely-packed infantry.
  • Siege Shells - Siege Shells are used against enemy structures and fortifications. They are fused to explode after hitting the ground, causing damage to the building's foundation.
  • Melta Shells - Melta Shells undergo a sub-atomic reaction upon impact and release a blast of intense heat. They are capable of doing tremendous damage to armoured units and infantry alike.
  • Inferno Rounds - Inferno Round shells are packed with a highly flammable substance such as an oxy-phospur gel or a thermite compound, causing everything in the vicinity of its explosion to burst into flame. This fire is difficult to extinguish and its flammable gel will stick to most surfaces. As a result, most infantry and vehicles will retreat when faced with a concentrated barrage of Inferno Rounds.
  • Illumination Shells - Illumination shells are fired high into the air on a parabolic arc where they deploy a parachute and slowly drift downwards. The shell burns very brightly on its way down to illuminate the battlefield for night operations.
  • Smoke Shells - Smoke Shells cover the impact area with a dense layer of smoke which is used to conceal the location of friendly forces.

Known Users of the Heavy Mortar Cannon

The Heavy Mortar Cannon is widely used by the Death Korps of Krieg's Siege Regiments, where even infantry companies possess their own light artillery support. In addition to the company's own guns, specialised Field Artillery Companies using the Heavy Mortar Cannon can be permanently attached to a given regiment or kept as autonomous reinforcements.

  • 19th Death Korps of Krieg Regiment, 38th Field Artillery Company - Used the Heavy Mortar Cannon during the Siege of Vraks.
  • 261st Death Korps of Krieg Regiment, 8th Field Artillery Company - Used the Heavy Mortar Cannon during the Siege of Vraks.
  • 143rd Death Korps of Krieg Regiment, 1st Field Artillery Company - Used the Heavy Mortar Cannon during the Siege of Vraks.

Adeptus Mechanicus Technical Specifications

Heavy Mortar Cannon
Vehicle Name: Heavy Mortar Main Armament: N/A
Forge World of Origin: Lucius Secondary Armament:


Known Patterns: I - VII Traverse: 0 degrees
Crew: 4 Gunners Elevation: 20 to 82 degrees
Powerplant: N/A Main Ammunition: N/A
Weight: 3.5 Tonnes Secondary Ammunition: N/A
Length: 4.6 metres Armour:
Width: 2.3 metres
Height: 3.3 metres Superstructure: N/A
Ground Clearance: 0.6 metres Hull: N/A
Max Speed On-Road: N/A Gun Mantlet: N/A
Max Speed Off-Road: N/A Vehicle Designation: 7556-307-9857-HM03
Transport Capacity: N/A Firing Ports: N/A
Access Points: N/A Turret:



  • Codex: Imperial Guard (2nd Edition), pg. 25
  • Imperial Armour Volume One - Imperial Guard (Second Edition), pp. 197-199, 267
  • Imperial Armour Volume Three - The Taros Campaign, pp. 233-235
  • Imperial Armour Volume Five - The Siege of Vraks - Part One, pp. 112-115
  • Imperial Armour Volume Six - The Siege of Vraks - Part Two
  • Imperial Armour Volume Twelve - The Fall of Orpheus, pg. 205


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