Weapons that mimic the gamma-ray pulse caused by a nuclear blast to knock out all electronics, including computers and automobiles, over wide areas. The phenomenon was discovered in 1962 after an aboveground nuclear test in the Pacific that disabled electronics in Hawaii.

The electromagnetic pulse or abrupt burst of electromagnetic radiation is caused by high energy explosions such as a nuclear blast, or by a suddenly fluctuating magnetic field. The resulting rapidly changing electric fields and magnetic fields may couple with electrical and electronic systems to produce damaging current and voltage surges.