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CRS Report for Congress

High Altitude Electromagnetic Pulse (HEMP) and
High Power Microwave (HPM) Devices:
Threat Assessments

Updated July 21, 2008

Clay Wilson
Specialist in Technology and National Security
Foreign Affairs, Defense, and trade Division






A Commission to Assess the Threat from High Altitude Electromagnetic Pulse

(EMP commission) was established by Congress in FY2001 after several experts

expressed concern that the U.S. critical infrastructure and military were vulnerable

to EMP attack.1 On July 20, 2008, the Commission presented a report to the House

Armed Services Committee (HASC) assessing the effects of an EMP attack on U.S.

critical national infrastructures. The 2008 report contained analysis of results of tests

for modern electronics and telecommunications equipment for public networks

supported by the power grid and by temporary isolated power supplies, including cell

phones, computer servers, and Internet routers and switches. The report also made

recommendations for preparation, protection, and recovery of U.S. critical

infrastructures from EMP attack.


The Commission reported that the ubiquitous dependency of society on the

electrical power system, coupled with the EMP’s particular damage mechanisms,

creates the possibility of long-term, catastrophic consequences for national security.

Comparison was made to hurricane Katrina in 2005, where the protracted power

blackout exhausted the limited fuel supplies for emergency generators. However, in

the case of an EMP attack, a widespread collapse of the electric power grid could

lead to cascading effects on interdependent infrastructures, possibly lasting weeks or

months. The Commission stated, “Should significant parts of the electrical power

infrastructure be lost for any substantial period of time ... many people may

ultimately die for lack of the basic elements necessary to sustain life in dense urban

and suburban communities ... [and] the Federal Government does not today have

sufficiently robust capabilities for reliably assessing and managing EMP threats.”2


1Michael Sirak, “U.S. vulnerable to EMP Attack,” Jane’s Defence Weekly, July 26, 2004,


2Report of the Commission to Assess the Threat to the United States from Electromagnetic

Pulse (EMP) Attack; Critical National Infrastructures, Apr 2008,, and p.79.

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