Editing Battle of Calth (section)

==Opening==
The Word Bearers were not terribly subtle about their shady intentions, but Guilliman and his Legion were unprepared for a treacherous attack from a presumed friendly force. The first action Erebus's forces took was to attack a maintenance vessel, the ''Campanile'', and take it over without the Ultramarines noticing. The Word Bearers began a ritual that would implant Chaos-infected scrapcode into the Calth orbital defense network while they deployed to the planet's surface under the cover of beginning coordination with the Ultramarines.

Being the efficient pragmatists that they were, the Ultramarines had a system for post-battle analysis. One of the key components of this was the "Mark" system, where all forces would record a certain time for the official start of the battle (Mark Zero) and record actions based on that initial time point. Twenty minutes prior to Mark Zero of the Battle of Calth, the ''Campanile'', moving at a significant percentage of lightspeed, crashed into the Calth orbital docks. Tens of thousands died in the resulting cascade of explosions, and dozens of ships were destroyed or crippled. Seconds later, the Word Bearers fleet opened fire on the Ultramarines. After Guilliman's urgent plea for a ceasefire was ignored and Lorgar openly declared his traitorous intentions, he gave the order to fire back, officially beginning the battle.