After aliens overran earth and after a long struggle, the military decided to drop nuclear bombs over all major cities. Some say it was to target areas with high amounts of aliens. Others claim that the military had switched sides for some unknown reason, but nobody really knows what is going on. Earth Taken 2 kicks off right after all the nuclear bombs have fallen. Radiation has spread all over the planet and you are sure to encounter some of it. A RAD is an "absorbed radiation dose" and 500 would be enough to kill you.