The end of the world as we know it. The end by natural events, or the end by the hand of a lunatic? Either way preparation is essential for the survival of survivors and our children. Would the worse scenario be the shift of the Earths' skin to a new polar site, or nuclear war? It might be a good time to search for high ground with little historical sysmic activity.

Where Do You Go?
Once you're certain that foreign forces are heading for your community, you should have an escape plan in mind, that you have already scouted, and mapped out, preferably months in advance.
(If you have a moment, use Google Earth to give you a general idea of different wilderness areas you – if you're still here – can flee to in your state. When you have two or three areas in mind, go to a backcountry store that sells topographical maps (such as "Green Trails" maps), and you can easily locate hiking trails, creeks, rivers, and small lakes, elevation points, and even identify different types of terrain, which will give you a better idea of exactly what you're up against.)

You also should have a compass that you've practiced using, so that when the time comes to flee into the wilderness, you'll know how to find your way without getting lost.
(If you live in a southern state, consider heading North, and seek out an area that receives plenty of rain. You'll have much better odds at survival, and less odds of dying of heat stroke or wildfire.)

Consider a destination many miles away from any roads, however that is close to rivers, forest, meadows, and even one or more small lakes.
This will put distance between you and invading forces, as well as provide suitable hunting, fishing, trapping, and fresh water sources.

Make sure the route you choose to get there doesn't include rivers that are impossible to cross. If you do come to a river that's impassable, the only option you may have is to hike along the banks, until you come to the narrowest / shallowest part of the river, and that's where you can consider making your crossing.