EMP refers to any electromagnetic pulse meant to damage or destroy electrical systems.  It can be generated intentionally with an electromagnetic weapon (IEMI) for a local attack or, for broad regional or even national coverage, as a High Altitude EMP (HEMP): a sudden, intense pulse of electromagnetic energy resulting from a nuclear detonation in space.   It could damage or burn out the electrical grid, computers, telephones, water supply and other critical infrastructures of a region, a nation or an entire continent.

In 1962, deep in a cold war with the Soviet Union, the United States conducted “Starfish Prime,” a nuclear weapon test over a remote region of the Pacific Ocean.  The test was successful, with one unexpected result: Fifteen hundred kilometers away streetlights burned out, TV sets and radios failed and power lines fused in parts of Hawaii.  Three similar Soviet tests that same year over Kazakhstan caused more serious infrastructure problems, long before the delicate and ubiquitous microchips that power today’s world.

A nuclear warhead set off above the atmosphere causes a High Altitude Electromagnetic Pulse, or HEMP.  Unlike a ground burst, a HEMP strike could cause catastrophic damage over broad areas of a continent, a capability now in the hands of any rogue nation or terror organization that can acquire a single nuclear-tipped missile.

HEMP is not new.  The threat was a central element of the superpowers’ nuclear confrontation throughout the cold war.

Since the first atmospheric nuclear tests fifty years ago, it has been known that a single nuclear weapon exploded above the Earth’s atmosphere produces this high altitude electromagnetic pulse, radiating down to the Earth in a massive electrical surge of over 10,000 volts per meter.  An EMP weapon’s range depends on its altitude: it hits everywhere on a continent not blocked by the earth’s curvature and strikes about ten times as fast as lighting.  It has the potential to damage or destroy computers, electronics and critical control systems that could, in turn, destroy much or most of a nation’s electric grid, with damage to critical components that could mean a blackout lasting months or even years.

Throughout the cold war the U.S. and Russia had extensive HEMP laboratories and testing programs, viewing it as the first step in a nuclear war.  As an indication of the two nations’ HEMP concerns, in 1995 Russian fears of a possible HEMP attack brought the world close to a massive nuclear exchange, due to miscommunication regarding Norway’s launch of a single rocket carrying a weather tracking satellite.