For the first time I noticed what seems to be a big gap in the fluff for the Battle of Macragge. The Tyranid codex says that after Cold Steel Ridge the Ultramarines focused their forces in the polar fortresses, and the Tyranids attacked them there. But what about the rest of the planet? Macragge is the capital of the Ultramar system, and it has a sizeable population. Its never mentioned that the Marines brought them to the Polar fortresses, so what happened to them? Did the Ultramarines just let the Tyranids nom them all? In the old codex I remember it talking about titans fighting against the hordes on the ice fields, but there is no way they could defend population centers by themselves. So did the Tyranids just completly (or mostly) ignore the big buffet of biomass to go straight for the remaining marines, or was the population mostly absorbed and it just doesn't mention it? And what about their fortress monastey (The Fortress of Hera if I remember right)? Did they just leave it undefended, as it says that all of the First company was at the Polar fortresses, and it doesn't seem to imply that any other companies had a major prescence on the surface.