Gaia, as it called by humans was discovered after ww3 erupted. It quickly dissolved into a nuclear war that plunged the planet into a nuclear winter and killed millions. Scientists frantically searched through their list of planets they thought would support life and a way to get there. And a way to keep those being saved alive long enough to get to this planet. The ones on the rocket, along with the supplies they where sent with,  where placed in a cryogenic sleep and the  coordinates where programmed with the hope they would make it to humanities salvation. The rocket, whether in their rush the scientists entered the coordinates wrong or the rocket was pushed off course, found Gaia. But the planet wasn't as empty of life as they thought. Creatures they thought of as myth on earth resided on this planet. These where the aliens they always speculated about. They had already resided on earth. And they didn't take kindly to these travelers. With no way back, humanity fought. The war waged for a hundred years bloody years. But with it came a surprise. Humans that had known of these creatures on earth, where where once scorned at by society, became its salvation. They found a way to fight back and the war ended in a truce. Now, they co exist. Or try to