An Electromagnetic Pulse attack could result in the greatest loss of life in human history, but most people have never heard of an EMP.
An EMP can be triggered by detonating a nuclear warhead above the earth’s atmosphere, which would release a pulse of energy that could destroy electrical grids and electronics such as cell phones and computers over a thousand-mile radius.
“What happens when, when the grid comes down, is there are surges of electricity that blow the big transformers,” Roscoe Bartlett, a former member of the House of Representatives who spearheaded the creation of a Congressional EMP Commission, said. “The estimate is that we could lose somewhere between 100 and 200 of those; that means that the grid would be down for a year or more.”
The Congressional EMP Commission reported that after such an attack Americans would face starvation, a lack of clean water, disease and eventually societal unrest. The commission estimated that 90 percent of the U.S. population would die within a year — nearly 300 million people.
http://www.theblaze.com/stories/2016/02/08/for-the-record-understanding-the-threat-of-emp