This discussion seems a little abstract. If we use WW2 as a reference, we see that there were different kinds of areas: the battle zone, the occupied zone, the not-yet-invaded zone, etc. There are probably many others. Based on years of watching war movies, I'd say your prep for each zone is different. Where do you expect to be?

If you're in a battle zone, then you should probably run. You'll forget about your huge stash of food, fuel, etc. if you want to live. The Syrian refugees would be your model. Grab some money, jewelry, passport, cellphone, and go. Use social media to find out where you should go, how you can get there, where you can stay on the way, etc.

If you're in an occupied zone or a not-yet-invaded zone, Blast's advice would apply more probably. I'm not sure what one should do to prepare for being occupied by enemy forces. Maybe we can look at France, Poland, China, etc. for examples. Get ready to lose your liberty.

Being in a not-yet-invaded zone is great, and much of your life can continue as before -- though with reduced material comfort, food scarcity, etc. But your government might just go nuts with suspicion and imprison entire families without due process. I don't see any preparation that would have helped Americans of Japanese or German descent during WW2, or for that matter the Indians who lived on the outskirts of Alaska. One family gave their farm to their neighbors before they were dragged off to the concentration camp, and the neighbors were decent enough to work the land and give the farm back after the war was over. But this sort of stuff falls under "true challenges of human character" rather than emergency preparation techniques.

These are just some ideas off the top of my head.