The Humans, well the remaining humans, were orginally of
the most elite class of those in their society that were put in
the deep underground arcologies when the humans began the nuclear
strikes against their own planet that brought around the apocalypse.
But, after the many unknown decades went by and the humans eventually
left their underground hiding, they discovered their plan had
failed and what they had attempted to destroy, remained.
Development
of protection from the contaminant produced a special energy shielding
that surrounds all of the human assets: vehicles, buildings, and
the people themselves. And also, the humans retained control of
old weapons satilletes in the planet's orbit and are able to provide
devastating firepower to rain down from above on key positions.
Your
beginnings in the war as the humans will begin just outside of
the Ark I, from which the humans emerged again, and now they're
here to take their planet back for good.