It is true that your soldiers may outnumber mine.
But the ocean runs deep.
I am certain that you will run out of men, before the ocean runs out of space. -- Anon Guest
It only looked like a Graveworld. There were all the signs. Ruined buildings in the midst of assorted plants run amok. Domesticated animals turned wild, creating an ecology of their own. There were even apocalypse journals left where they might survive until discovery.
More Graveworlds were caused by monoculture abuse than war. This one was one of the former.
Those resettling the world wondered about the occasional references to "the underpeople," but could not find any tunnels or signs of subsurface habitation. In retrospect, they should have looked further than the land masses.