“And EMP device is targeted and we may not even know that it was ignited except that everything stops working. “
What kind of education do you have to think a nuclear blast has no visible signature, no heat, no nuclear radiation and would go unnoticed? Do you really believe EMP is some kind of stealth device?
You believe all that childish EMP crap yet you know nothing of nuclear detonations or the nuclear detection capabilities, which, BTW, are on nearly every single US satellite including GPS, of the US?? Really? That ignorant of it all?
And yes, a well designed EMP device may not be visible.
I have worked extensively EMC (Electro Compatibility Testing). That means emissions compliance testing and immunity testing.
ALL of the electromagnetic sources that make electronics vulnerable are not visible (not in the visible spectrum). No doubt, weapons experts designing an EMP device will know this and target ALL of the energy (amplitude and wavelength) into destroying the electronic devices.
BTW, a lot of military equipment IS SHIELDED. I saw a test facility. Interesting. But there is still a limit to the shielding.
A optimal attack would be a one-two punch — first, with an emp device, second after millions of people are trapped in a city, an actual thermo-nuke that kills.