After the 7 hour war, the remaining humans were gathered in cities, with the world outside of such areas filled with wildlife native to other worlds. This made the the exteriors of cities and the regions beyond dangerous if not downright deadly to not only human life but also to the rest of Earth's natural fauna. The rest of the planet was reduced to inhospitable wastelands. Facilities like Nova Prospekt were opened within the remnants of the remaining man-made infrastructure- their goals being to modify humans, erase their memories, and assimilate them into the Combine's workforce and military.