It all makes sense now.
Thanks guys
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In the blood-soaked Sabbat Worlds Crusade, the massed ranks of the Imperium battle the dark forces of Chaos for dominion. At the forefront of this conflict are the Imperial Guard – untold numbers of ordinary soldiers fighting to preserve the Emperor’s holy realm. 'Colonel-Commissar Ibram Gaunt and the men of the Tanith First-and-Only are at the heart of this struggle. 'Forced to flee their planet before it was destroyed by Chaos, they are the last of their breed. This, together with their peerless scouting ability, has earned them the nickname the ‘Ghosts’. With unmatched tactical acumen, experts in covert operations, they're dispatched to the very worst hellholes in the galaxy.
Imperial Lexicanum