When Americans think about the threat from foreign missiles, it’s nearly always the catastrophic effect of a conventional nuclear blast that comes to mind. We think of the doomsday scenarios that have played out in many movies and TV shows: A nuke explodes over a large city - leveling buildings, crushing houses and creating a swath of destruction.

But that’s not the only threat that can come from a missile fired from a rogue nation or one that has fallen into the hands of terrorists. We also could fall victim to the devastating effects of an electromagnetic pulse. With an EMP, almost everything powered by electricity would effectively be wiped out - not physically, but practically. Such things would simply cease to work.

Imagine the havoc this could cause. Your cellphone? Useless. The same goes for your TV, radio and computer. Your car might still run, but good luck driving on roads with no working stoplights, accessing your GPS devices for directions or buying gasoline from pumps that won’t pump. We’d be in the dark, literally - plunged into the early 19th century in a matter of seconds.

Sound like science fiction? It’s understandable that some people would think so, especially anyone who has seen the flashy EMP attacks dramatized in TV shows such as “24.” Unfortunately, it’s all too real. Why? Because an EMP isn’t an altogether new, high-tech weapon. It’s the same nuclear blast we’ve come to fear as a potential destroyer of our cities. It’s just used in an alternate way.

The difference: the location of the blast. In a conventional nuclear attack, the bomb is timed to explode close to the ground. The resulting radiation blast wreaks great physical damage. But with an EMP, the same kind of bomb is set to explode high in the air. When that happens, the blast doesn’t level a city, but it does knock out the power grid, leaving the residents who have come to depend on it largely helpless.

And who among us doesn’t depend on electricity? What a chaotic, dangerous mess this weapon could leave in its wake. Everyday life would grind to a halt. Almost every feature of 21st-century life on which we’ve come to rely, from fully stocked grocery stores to fire and ambulance services, would be gone in an instant.

We can’t take comfort in the thought that an EMP is something beyond the reach of a rogue nation or terrorist group. “Several potential adversaries have or can acquire the capability to attack the United States with a high-altitude nuclear-weapon-generated electromagnetic pulse,” the 2004 Commission to Assess the Threat to the United States From Electromagnetic Pulse Attack reported. “A determined adversary can achieve an EMP attack capability without having a high level of sophistication.”

The threat of an EMP attack makes it all the more imperative that we pursue an immediate and comprehensive missile defense. Missile defense was conceived as a way to counter a conventional nuclear attack. But there’s no reason it can’t serve a dual purpose. The same missiles that can knock down a rocket delivering a low-altitude nuclear payload can do the same to a high-altitude one equipped with an EMP.

But we need to ensure that the system we deploy can do the job. That’s what I mean by “comprehensive.” We need to make it a layered system - one on land and sea and in the air and with the ability to take out missiles in almost any stage of flight. What the Obama administration is proposing, in terms of funding and design, simply won’t do the job.

That’s unacceptable. The EMP threat isn’t going away - at least, not until we show that we’re serious about disarming it. The sooner, the better.

Ed Feulner is president of the Heritage Foundation.