all people forced to live under the United Empire States, which includes Starship Troopers, The Covenantfrom halo, the Enclave from Fallout, Tau from 40k. 
ancient Celts villages near river. 
Star wars Clones and Mandalorian rebels fighting UES or the united Empire States.
The enemies are the Reapers invasion mass effect, The Galactic Empire, Warhammer 40,000, the combine, Predator Yautja Hunters,
people from other worlds found worm holes to this universe, now all are fighting for it. evangelion