A Legion Breacher Siege Squad was a specialised formation of the ancient Space Marine Legions used during the Great Crusade and Horus Heresy eras in the late 30th and early 31st Millennia. Breacher Siege Squads utilised specialised tactics and wargear for the explicit purpose of acting as a vanguard assault force in the worst combat conditions imaginable and in the direst of war zones, known to the Legions as "Zones Mortalis" for the sheer likelihood of death faced by any who were forced to fight within them.
The most harzardous and desperate spheres of warfare such as boarding actions amid the cold void of space and the forlorn hope of the first wave of attackers into a breached fortress often proved lethal beyond endurance, even for the warriors of the Legiones Astartes. For this reason, since the early days of the Great Crusade, specialised forms of wargear and tactics had been under continuous development to cope with these "Zones Mortalis". Several of the Legions, such as the Imperial Fists, World Eaters and the Iron Warriors, had even made these bloody modes of warfare their particular concern. Breacher Siege Squads were units of Space Marines equipped with specialised arms and employing specially customised and augmented suits of hardened Power Armour, usually variants on the Mark III Iron Pattern, modified by the Legion's Techmarines to better withstand the rigours of siege warfare, lethal environments and close-quarters boarding actions in space. Breacher Siege Squads often employed heavy ablative shields to resist enemy fire and specialised breaching charges and lascutters to bypass bulkheads and shatter internal strongpoints. The servos and power systems of their armour were often overstrained as a result of these modifications, and required constant extensive maintenance between battles. This deficiency was one of the factors that ultimately led the Mechanicum to undertake the Tactical Dreadnought Armour development project in the last years of the Great Crusade.
Optional Wargear (Sergeant Only)
- Artificer Power Armour
- Plasma Pistol
- Power Weapon
- Power Fist
- Single Lightning Claw
- Thunder Hammer
- One Breaching Charge
- Melta Bombs
- Imperial Armour - The Horus Heresy - Book One: Betrayal, pp. 72, 204
- Forge World - Legion MK III Breacher Squad