Heavensreach is the last real Imperial bastion in the Pegasus Gulf. It is the bulwark on which the orkish hordes will break themselves, should all things go according to plan. The Angels of Solace space marine chapter has established a semi-permanent fortress on the world, alongside a token Dark Angels presence. In combination with the Heavensreach Death Brigades, a ten million man standing army of elite soldiers, it makes Heavensreach a frightening place to invade. Prospects are made worse for attackers in that Heavensreach's main population centres are fashioned after the fortress cities of Cadia, the Kasrs.
Since the Imperial defeat at Persephone, the Imperials in the Gulf have been focusing on fortifying the region of space surrounding Heavensreach, as well as the planet itself should worst come to worst. What were once green fields are now barren landscapes, bombed into a radioactive waste deliberately in order to prevent orkish infestation. Should orkoid lifeforms take root in the irradiated hellscape, they will be easily found and flushed out with nowhere to hide. For miles around each Kasr, a honeycomb of labyrinthine trenches add to the cities' formidable defences.
Heavensreach will not be taken easily.