Loyalist victory The Ultramarines burn the traitors out of the arcologies; the surviving Word Bearers are left to die underground.
The poisoned Veridia scorched Calth’s surface with lethal radiation, and the surviving Ultramarines together with millions of citizens went beneath the crust — into gigantic arcologies and tunnel cities. There began a war without a sky: seven years of ambushes, demolished vaults and gallery assaults against the Word Bearers, trapped on the planet with those they had betrayed. Captain Remus Ventanus gathered scattered companies and led them to burn out the enemy level by level. The XIII Legion won and cleansed Calth, but the campaign tied its forces to its home sector for almost the whole of the Heresy.
Sides
Traitors
Legions
- Type
- Battle
- Scale
- 3 of 5
Significance
Seven years — half the span of the Heresy — the Ultramarines are bound by the Underworld War and do not come to Terra’s aid.
Disputed in the canon
- The window 007–014.M31: Lexicanum (“Underground War”) carries the underground fighting from the Battle of Calth right up to the Siege of Terra, but the canon gives no dated battles within the window — the count is by years. The date is therefore disputed, and the event stands at the start of the window, directly after the Battle of Calth and the Betrayal at Ithraca: the stated year (007.M31) is merely the beginning of a multi-year war.
Sources
- Lexicanum: Underground War
- Lexicanum: Calth
- Lexicanum: Remus Ventanus
- Mark of Calth (anthology, BL)
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