Let's assume for a moment that there are different cycles a…

Let's assume for a moment that there are different cycles at work, one within the other similar to a Mayan calendar. There are of course bigger and smaller ones, but for now let's focus on only two: The cycle of civilization and the disaster cycle. The ideal moment for the hot phase of the disaster cycle wouldn't be the hight of a civilization when it is strongest. The ideal scenario is that the civilization cycle is also in it's very last phase. That's when the "soil" is most fertile and able to support the few seeds that survive and provide them with what they need. Storable, readily available information, advanced technology, weapons and highly concentrated energy and fuels.