Without being snarky, what is the point of your war ? It's illuminating that the victors in a war always knew what it was. And until they did, they weren't the victors.
This is why invasions are so so so so so so so difficult. Yes, you can rush in, "Blitzkrieg" if you like. But having done that, what next ? Unless you can cleanly decapitate and impose your own immediate administration, you haven't really "won".
In the impossible event the Nazis had managed to occupy and control Britain, there were auxiliary units (sort of SOE:UK) tasked with harassing them. I think it was Alice Roberts in a recent documentary that found a hidden message drop that a vicar had prepared for use in the event.
And Iran has had years to arrange this sort of defence.