Ever heard of Electromagnetic pulse, or EMP? Probably not, unless you’re a nuclear weapons expert.  

In the 1950's, At the dawn of the nuclear age, most weapons analysts focused on the unparalleled death and destruction even one nuclear weapon would cause. Bomb blast, fireball, radiation poisoning. But few thought about electromagnetic pulse -- the invisible wave of electricity that would fry electronic circuits seemed almost trivial.

But fast forward 60 years to modern, high tech America. Today every aspect of our lives depends on electronics, computers, the Internet and satellites - our armed forces, our banking system, our communications networks, our infrastructure.

What if the electricity suddenly went out? One nuclear warhead detonated high above North America would produce a shockwave powerful enough to knock out the entire electric grid and all electronic devices. Not just a temporarily because the system was overloaded, but a permanently because the circuits were fried.

Nothing would work – not the phone system, or water pumping stations, or planes, trains or automobiles. Your toilet wouldn’t flush and the TV wouldn't turn on. Planes would stop in mid air. The only way to communicate would be face to face. Credit cards would be useless.

Tens of millions would die of disease and starvation. We would be thrown, unprepared and within seconds, into a pre-electric world. America would likely never recover. Unthinkable? 

Think again.

Who would do it to us? Who could? Any country with the ability to shoot a nuclear tipped missile at the US. That’s China and Russia today or North Korea and Iran tomorrow.

It's time we start thinking about the unthinkable.

Is there anything we can do now? Here are three suggestions:

First, the Obama administration must redouble efforts to stop rogue states like Iran from getting nuclear weapons, using force if necessary. 

Second, President Obama should reverse his decision to cut back the missile defense program. If we can't prevent nuclear proliferation we must take steps to defend ourselves from attack. 

Finally, we should spend the $100 million dollars necessary to harden the electric grid and national infrastructure. It won't protect us from an EMP attack, but it could save the country from catastrophe.

Kathleen Troia "K.T." McFarland served in national security posts in the Nixon, Ford and Reagan administrations. She wrote Secretary of Defense Weinberger's November 1984 "Principles of War Speech" which laid out the Weinberger Doctrine. She is a senior adviser to the Foundation for the Defense of Democracies and a frequent contributor to the Fox Forum. Watch "K.T." and Mike Baker every Monday at 10 a.m. on FoxNews.com's "DefCon3."