Certain areas of the world have been in low-level war off and on for years and years. Seems like that might be the baseline of what it looks like no matter where it's actually happening.

The zombies have been looking for nukes and have been learning how to make dirty bombs so these might be factors in III that weren't present in I and II. Knowing some basic precautions in that/those events could prove useful.

Seems like widespread conflicts reduce down to "tribe" or "me and mine" in terms of people banding together or deciding who is in or out of the sphere of help. It also decides who gets drafted to go risk or forfeit their lives for the State.