Order Code RL32544
CRS Report for Congress
Received through the CRS Web
High Altitude Electromagnetic Pulse (HEMP) and
High Power Microwave (HPM) Devices:
Threat Assessments
August 20, 2004
Clay Wilson
Specialist in Technology and National Security
Foreign Affairs, Defense, and Trade Division
Congressional Research Service ˜ The Library of Congress

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High Altitude Electromagnetic Pulse (HEMP) and High
Power Microwave (HPM) Devices: Threat Assessments
Summary
Electromagnetic Pulse (EMP) is an intense energy field that can instantly
overload or disrupt numerous electrical circuits at a distance. Modern high
technology microcircuits are especially sensitive to power surges, and the possible
vulnerability of U.S. civilian computer systems to the effects of EMP has been
discussed in the media. EMP can be produced on a large scale using a single nuclear
explosion, and on a smaller, non-nuclear scale using a device with batteries or
chemical explosives. Several nations, including reported sponsors of terrorism, may
currently have a capability to use EMP as a weapon for cyber warfare or cyber
terrorism, to disrupt computers, communications systems, or parts of the U.S. critical
infrastructure.
The threat of an attack against the United States involving EMP is hard to
assess, but some observers indicate that it is growing along with worldwide access
to newer technologies and the proliferation of nuclear weapons. In the past, the threat
of mutually assured destruction provided a lasting deterrent against the exchange of
multiple high-yield nuclear warheads. However, now a single, specially-designed
low-yield nuclear explosion high above the United States, or over a battlefield, can
produce an EMP effect that results in a widespread loss of electronics, but no direct
fatalities, and may not necessarily evoke a large nuclear retaliatory strike by the U.S.
military. This, coupled with the possible vulnerability of U.S. commercial electronics
and U.S. military battlefield equipment to the effects of EMP, may create a new
incentive for other countries to develop or acquire a nuclear capability.
Policy issues raised by this threat include (1) what is the United States doing to
protect civilian critical infrastructure systems against the threat of EMP, (2) does the
level of vulnerability of U.S. civilian and military electronics to large-scale EMP
attack encourage other nations to develop or acquire nuclear weapons, and (3) how
likely are terrorist organizations to launch a smaller-scale EMP attack against the
United States?
This report will be updated as events warrant.

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Contents
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Questions about Vulnerability to EMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Electromagnetic Pulse Weapons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Description of High-Altitude Electromagnetic Pulse . . . . . . . . . . . . . . . . . . 3
Description of High-Power Microwave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Disruptive Capabilities of HEMP and HPM Weapons . . . . . . . . . . . . . . . . . 4
Hardening Against HEMP and HPM Weapons . . . . . . . . . . . . . . . . . . . . . . . 6
DOD Applications of HEMP and HPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Capabilities of Other Nations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Ground Wave Emergency Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Policy Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Private Sector Vulnerability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Military Vulnerability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
New Incentive to Develop a Nuclear Capability . . . . . . . . . . . . . . . . . . . . . 12
Terrorist Use of HPM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Human Rights Objections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Legislative Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
CRS Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

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High Altitude Electromagnetic Pulse (HEMP)
and High Power Microwave (HPM) Devices:
Threat Assessments
Background
A Commission to Assess the Threat from High Altitude Electromagnetic Pulse
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 A recent
briefing given to the Securities Industry Automation Corporation (SIAC) by panel
members from the commission reportedly highlighted what they termed as
deficiencies in the U.S. government’s readiness to protect against a high-altitude
nuclear burst which could emit electromagnetic energy powerful enough to
permanently disable many critical infrastructure computers. At a July 22, 2004
hearing before the House Armed Services Committee, panel members from the
commission reportedly stated that as U.S. military weapons and control systems
become more complex, they may also be increasingly vulnerable to the effects of
EMP. The consensus of the commission is that a large-scale EMP attack could
possibly cause widespread damage to unprotected civilian and military electronic
equipment for an extended period.2
Some observers indicate that the threat of an EMP attack against the United
States may be growing along with worldwide access to newer technologies and the
proliferation of nuclear weapons.3 A single, specially-designed, low-yield nuclear
explosion high above the United States, or over a battlefield, can produce a large-
scale EMP effect resulting in widespread loss of electronics, but possibly without
direct fatalities. In the past, the threat of mutually assured destruction provided a
lasting deterrent against the exchange of multiple high-yield nuclear warheads.
However, an EMP attack directed against the United States involving no violent
destruction, nor instant death for large numbers of U.S. citizens, may not necessarily
evoke massive nuclear retaliation by the U.S. military, where, for example, large
numbers of innocent civilians of a nation with a rogue leader might be killed. Today,
the perceived lower risk of assured destruction by the United States, and the
perceived vulnerability of U.S. civilian and U.S. military computers to the effects of
1 Michael Sirak, “U.S. vulnerable to EMP Attack,” Janes’s Defence Weekly, July 26, 2004,
[http://www.janes.com/defence/news/jdw/jdw040726_1_n.shtml].
2 Daniel G. Dupont, “Panel Says Society At Great Risk From Electomagnetic Pulse Attack,”
Inside the Pentagon, July 15, 2004, p.1.
3 U.S. Congress, House Armed Services Committee, Committee Hearing on Commission
to Assess the Threat to the United States from Electromagnetic Pulse Attack, July 22, 2004.

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CRS-2
an EMP attack may create a new incentive for other countries to develop or acquire
a nuclear capability.
Questions about Vulnerability to EMP
Some analysts discount the likelihood of a large-scale EMP attack against the
United States in the near term, and the extent of damage, stating that the critical
infrastructure reportedly would survive, and that military communications would
continue to operate and a high percentage of civilian phone calls would continue to
connect. These analysts reportedly state that limited testing has shown that modern
commercial equipment may be surprisingly resistant to the effects of electromagnetic
pulse, and that some military systems using commercial equipment are also
retrofitted to be made more EMP resistant before they are fielded.4 However, other
analysts reportedly state that some testing done by the U.S. military may have been
flawed, or incomplete, leading to faulty conclusions about the level of resistance of
commercial equipment to the effects of EMP. These analysts point out that EMP
technology has been explored by several other nations, and as circuitry becomes more
miniaturized, modern electronics become increasingly vulnerable to disruption. They
predict that it could possibly take years for the United States to recover fully from
widespread damage to electronics resulting from a large-scale EMP attack.5
Electromagnetic Pulse Weapons
An electromagnetic pulse (EMP), characterized as an energy weapon potentially
threatening to national security, usually is created by two methods. High-Altitude
Electromagnetic Pulse (HEMP) is an electromagnetic energy field produced in the
atmosphere by the power and radiation of a nuclear explosion, and that is damaging
to electronic equipment over a very wide area, depending on the design of the nuclear
device and altitude of the burst. High-Power Microwave (HPM) is an
electromagnetic pulse produced with special equipment that transforms power from
batteries, or from a chemical explosion, into intense microwaves that are very
damaging to electronics within a much smaller area.
In addition, while HEMP weapons are large in scale and require a nuclear
capability along with technology to launch high altitude missiles, HPM weapons are
smaller in scale, involve a much lower level of technology, and may be within the
capability of many non-state organizations. HPM can cause damage to computers
similar to HEMP, although the effects are limited to a much smaller area. The
4 Stanley Jakubiak, statement before the House Military Research and Development
Subcommittee, hearing on EMP Threats to the U.S. Military and Civilian Infrastructure,
Oct. 7, 1999.
5 Lowell Wood, Statement before the House Military Research and Development
Subcommittee, hearing on EMP Threats to the U.S. Military and Civilian Infrastructure,
Oct. 7, 1999; Jack Spencer, “America’s Vulnerability to a Different Nuclear Threat: An
Electromagnetic Pulse,” The Heritage Foundation Backgrounder, No.1372, May 26, 2000,
p.6.; and Carlo Kopp, “The Electromagnetic Bomb — A Weapon of Electrical Mass
Destruction,” Air and Space Power, 1993, [http://www.airpower.maxwell.af.mil/
airchronicles/kopp/apjemp.html].

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CRS-3
technical accessibility, lower cost, and the apparent vulnerability of U.S. civilian
electronic equipment could make small-scale HPM weapons attractive for terrorist
groups in the future.
Description of High-Altitude Electromagnetic Pulse
HEMP is produced when a nuclear weapon is detonated high above the Earth’s
surface, creating gamma-radiation that interacts with the atmosphere to create an
intense electromagnetic energy field that is harmless to people as it radiates outward,
but which can overload computer circuitry with effects similar to, but causing
damage much more swiftly than a lightning strike.6 The effects of HEMP became
fully known to the United States in 1962 during a high-altitude nuclear test (code
named “Starfish Prime”) over the Pacific Ocean, when radio stations and electronic
equipment were disrupted 800 miles away throughout Hawaii. The HEMP effect can
span thousands of miles, depending on the altitude and the design and power of the
nuclear burst (a single device detonated at an appropriate altitude over Kansas
reportedly could affect all of the continental United States)7, and can be picked up by
metallic conductors such as wires or power cables, acting as antennas to conduct the
energy shockwave into the electronic systems of cars, airplanes, and communications
equipment.
Description of High-Power Microwave
HPM is a non-nuclear radio frequency energy field. It can be produced as a
weapon when a powerful chemical detonation is instantly transformed by a special
coil device, called a flux compression generator, into a strong electromagnetic field
of microwave energy.8 Other methods, such as powerful batteries, can also be used
to create a reusable HPM weapon. HPM energy can be focused using a specially-
shaped antenna, or emitter, to produce effects similar to HEMP, but only within a
very limited range. Unlike HEMP, however, HPM radiation is comprised of shorter
wave forms at higher-frequencies, which make it highly effective against electronic
equipment and more difficult to harden against. A mechanically simple, suitcase-
sized device, using a chemical explosive and special focusing antenna, might
6 A nuclear explosion produces gamma rays, which interact with air molecules in a process
called the Compton effect. Electrons are scattered at high energies which ionizes the
atmosphere, generating a powerful electrical field. This EMP effect is strongest at altitudes
above 30,000m, and lasts so briefly that current cannot start flowing through a human body
to cause harm to people. [http://www.physics.northwestern.edu/classes/2001Fall/Phyx135-
2/19/emp.htm].
7 The Federation of American Scientists, “Nuclear Weapons EMP Effects,”
[http://www.fas.org/nuke/intro/nuke/emp.htm].
8 A Flux Compression Generator consists of explosives packed inside a cylinder, all of
which is contained within a cylindrical copper coil structure. The explosive is detonated
from rear to front, causing the tube to flare in a wave that touches the copper coil, which
produces a moving short circuit. This compresses the magnetic field and creates an
electromagnetic pulse that is emitted from the front end, which is then directed by a special
focusing antenna. [http://www.physics.northwestern.edu/classes/2001Fall/Phyx135-
2/19/emp.htm].

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CRS-4
theoretically produce a one-time, instantaneous HPM shockwave that could disrupt
many computers within a 1-mile range.9 Also, HPM energy at higher power levels
(megawatts), and powered for a longer time interval, reportedly could cause physical
harm to persons near the source emitter, or possibly in the path of a narrowly focused
energy beam.10
Disruptive Capabilities of HEMP and HPM Weapons
Studies related to the effects of electromagnetic weapons have been published
infrequently, or remain classified.11 Nevertheless, it is known that a powerful HEMP
field as it radiates outward can interfere with radio frequency links and disrupt
electronic devices thousands of miles from the nuclear explosion. Effectiveness is
increased if the electronic devices are connected to any metal that could also act as
an antenna. Because infrastructure computer systems are interconnected, a
widespread HEMP effect could lead to possible long-term disruption of power, fuel
distribution, transportation systems, food and water supplies, hospitals, and law
enforcement communications, as well as military communications systems which
utilize the civilian infrastructure.
A HEMP attack directed against the Unites States continent might involve a
one-megaton nuclear warhead, or a smaller one that is specially-designed, using a
burst several hundred miles above the mid-western states to affect computers on both
coasts.12 However, creating a HEMP effect over an area 250 miles in diameter, an
example size for a battlefield, might only require a rocket with a modest altitude and
payload capability that could loft a relatively small nuclear device. If a medium or
higher range missile with a nuclear payload were launched from the deck of a
freighter at sea, the resulting HEMP could reportedly disable computers over a wide
area of the coastal United States.
The disruptive effects of both HEMP and HPM reportedly diminish with
distance, and electronic equipment that is turned off is less likely to be damaged.13
9 Dr. Robert C. Harney, Naval Postgraduate School, Apr. 12, 2004, personal communication.
10 Victorino Matus, “Dropping the E-bomb,” The Weekly Standard, Feb. 2, 2003,
[http://theweeklystandard.com/Utilities/printer_preview.asp?idArticle=2209&R=9F0C22
5C3].
11 William Graham, Electromagnetic Pulse Threats to U.S. Military and Civilian
Infrastructure, hearing before the Military Research and Development Subcommittee,
House Armed Services Committee, Oct. 7, 1999; and Carlo Kopp, “The Electromagnetic
Bomb — A Weapon of Electrical Mass Destruction,” Air and Space Power, 1993, at
[http://www.airpower.maxwell.af.mil/airchronicles/kopp/apjemp.html].
12 [http://www.physics.northwestern.edu/classes/2001Fall/Phyx135-2/19/emp.htm].
13 Experts may disagree on whether the damaging effects of HPM actually diminish
following the familiar inverse-square-of-the-distance rule. Michael Abrams, “The Dawn of
the E-Bomb,” IEEE Spectrum, Nov. 2003, [http://www.spectrum.ieee.org/WEBONLY/
publicfeature/nov03/1103ebom.html]. Some experts state that the severity of HEMP effect
depends largely on the bomb design, so a specially-designed low yield bomb may pose a
(continued...)

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CRS-5
To produce maximum HEMP, a nuclear device must explode very high in the
atmosphere, too far away from the earth’s surface to cause injury or damage directly
from heat or blast. Also, HEMP produced by the nuclear explosion is instantaneous
— too brief to start current flowing within a human body — so there is no effect on
people. However, microwave energy weapons (HPM) are smaller-scale, are
delivered at a closer range to the intended target, and can sometimes be emitted for
a longer duration. These capabilities can cause a painful burning sensation or other
injury to a person directly in the path of the focused power beam, or can be fatal if
a person is too close to the microwave emitter.14 Both HEMP and HPM can
permanently immobilize vehicles with electronic ignition and control systems.
A high altitude nuclear explosion (that creates HEMP) produces three major
energy components that arrive in sequence, and which have measurably different
effects that can be cumulatively damaging to electronic equipment. The first energy
component is the initial energy shockwave which lasts about one microsecond, and
is similar to extremely intense static electricity that can overload circuitry for every
electronic device that is within line of sight of the burst. A secondary energy
component then arrives, which has characteristics that are similar to a lightning
strike. By itself, this second energy component might not be an issue for some
critical infrastructure equipment, if anti-lightning protective measures are already in
place. However, the rise time of the first component is so rapid and intense that it
can destroy many protective measures, allowing the second component to further
disrupt the electronic equipment. The third energy component is a longer-lasting
magnetic signal, from about one microsecond to one full second in duration. This
geomagnetic signal causes an effect that is damaging primarily to long-lines
electronic equipment. A localized magnetic effect builds up throughout the length
of the transmission lines and then quickly collapses, producing a
magnetohydrodynamic (MHD) “heave,” or “late-time,” power surge that overloads
equipment connected to the power and telecommunications infrastructure. This late-
time effect adds to the initial HEMP effect, and systems connected to long-lines
power and communications systems may be further disrupted by the combined
effects. Smaller isolated systems do not collect so much of this third energy
component, and are usually disrupted only by the first energy component of HEMP.15
An HPM weapon has a shorter possible range than HEMP, but it can induce
currents large enough to melt circuitry, or it can cause equipment to fail minutes,
days, or even weeks later. Recently, a U.S. Commanche helicopter, flying in New
13(...continued)
larger HEMP threat than a high yield bomb. Lowell Wood, statement before the House
Research and Development Subcommittee, hearing on EMP Threats to the U.S. Military and
Civilian Infrastructure, Oct. 7, 1999.
14 Victorino Matus, “Dropping the E-bomb,” The Weekly Standard, Feb. 2, 2003,
[http://theweeklystandard.com/Utilities/printer_preview.asp?idArticle=2209&R=9F0C22
5C3].
15 The Federation of American Scientists, “Nuclear Weapons EMP Effects,”
[http://www.fas.org/nuke/intro/nuke/emp.htm], and Report of the Commission to Assess the
Threat to the United States from Electromagnetic Pulse (EMP) Attack, Vol.1: Executive
Report 2004, p.5.

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CRS-6
York while performing a radar test involving HPM weapons, generated a low-level
energy pulse that reportedly disrupted for two weeks the global positioning systems
(GPS) being used to land commercial aircraft at an airport in Albany, New York.16
Older electrical components, such as vacuum tubes, are generally built more
massively, and are more tolerant of electromagnetic pulse. However, as modern
electronics shrink in size, circuitry is becoming increasingly vulnerable to
electromagnetic interference. Therefore, countries with infrastructure that relies on
older technology may be less vulnerable to the disabling effects of HEMP or HPM
than countries that rely on a higher level of technology.17
Hardening Against HEMP and HPM Weapons
Electronic equipment may be hardened by surrounding it with protective
metallic shielding which routes damaging electromagnetic fields away from highly
sensitive electrical components. This method, known as Faraday cage protection, is
traditionally used to protect electronic equipment from a lightning strike. However,
power surges HEMP or HPM weapons could possibly involve peak currents of tens
of millions of amps which can pass through a protective Faraday cage. Additionally,
equipment placed within a Faraday cage may also be made vulnerable by any wires
running into to the cage which can conduct the electromagnetic shockwave into the
equipment. Depending on the power level involved, points of entry into the shielded
cages can sometimes be protected from electromagnetic pulse by using specially-
designed surge protectors, special wire termination procedures, screened isolated
transformers, spark gaps, or other types of specially-designed electrical filters.
Critical systems may also be protected by increasing the number of backup units, and
by keeping these units dispersed and out of range of the electromagnetic pulse source
emitter.18
Hardening most military systems, and mass-produced commercial equipment
including PCs and communications equipment, against HEMP or HPM reportedly
would add from 3% to 10% to the total cost, if the hardening is engineered into the
original design. To retro-fit existing military electrical equipment with hardening
would add about 10% to the total cost.19
16 Kenneth R. Timmerman, “U.S. Threatened with EMP Attack,” Insight on the News, May
28, 2001, [http://www.insightmag.com/news/2001/05/28/InvestigativeReport/U.Threatened
.With.Emp.Attack-210973.shtml].
17 Lowell Wood, statement before the House Research and Development Subcommittee,
hearing on.EMP Threats to the U.S. Military and Civilian Infrastructure, Oct. 7, 1999.
18 Electrical systems connected to any wire or line that can act as an antenna may be
disrupted. [http://www.physics.northwestern.edu/classes/2001Fall/Phyx135-2/19/emp.htm].
Army Training Manual 5-692-2, April 15, 2001, “Maintenance of Mechanical and Electrical
Equipment at Command, Control, Communications, Computers, Intelligence, Surveillance,
and Reconnaissance (C4ISR) Facilities, HEMP Protection Systems, Chapter 27,
[http://www.usace.army.mil/publications/armytm/tm5-692-2/chap27VOL-2.pdf].
19 Lowell Wood, statement before the House Research and Development Subcommittee,
hearing on EMP Threats to the U.S. Military and Civilian Infrastructure, Oct. 7, 1999.

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CRS-7
DOD Applications of HEMP and HPM
Underground testing of nuclear devices done in 1992 at the Nevada Test Site
were designed to research protection techniques to harden military systems against
HEMP effects resulting from a nuclear exchange.20 The Limited Test Ban Treaty of
1963 prohibits nuclear explosions in the atmosphere, in space, and under water.
Since then, testing to calibrate the effects of large-scale HEMP on the critical
infrastructure has been restricted. The design of new simulators to help measure
these effects would call for complex computations to represent the large number of
possible interactions between components found in the circuit boards, network
connections, wireless systems, hardware modules, and operating environments of
modern electronic systems that support the critical infrastructure.
DOD research on pulsed-power HPM electromagnetic weapons is currently
being done at Kirtland Air Force Base, in Albuquerque, New Mexico. Weapons now
being developed by the U.S. military for electronic warfare can disrupt the trajectory
of missiles while in flight, and can overpower or degrade enemy communications,
telemetry, and circuitry. Other HPM weapons being tested by the military are
portable and re-usable through battery-power, and are effective when fired miles
away from a target. These weapons can also be focused like a laser beam and tuned
to an appropriate frequency in order to penetrate electronics that are heavily shielded
against a nuclear attack. The deepest bunkers with the thickest concrete walls
reportedly are not safe from such a beam if they have even a single unprotected wire
reaching the surface.21
During Operation Iraqi Freedom, many Iraqi command bunkers and suspected
chemical-biological weapons bunkers were deeply buried underground and thought
to be difficult to disable using conventional explosives. New HPM weapons were
reportedly considered for possible use in attacks against these targets because the
numerous communications and power lines leading into the underground bunkers
offered pathways for conducting powerful surges of electromagnetic energy that
could destroy the computer equipment inside.22 The term “non-kinetic” is sometimes
used to describe the group of weapons with the above capabilities. This term
includes weapons designed to emit directed energy that, in short pulses, may disable
computer circuitry, or in other applications, may cause temporary physical
discomfort.
HPM can sometimes injure persons in the path of the instantaneous microwave
power beam, or can be fatal if persons are too close to the energy-focusing antenna.23
20 Associated Press, “Experts Cite Electromagnetic Pulse as Terrorist Threat,” Las Vegas
Review-Journal, Oct. 3, 2001.
21 Michael Abrams, The Dawn of the E-Bomb, IEEE Spectrum Online, Nov. 2003,
[http://www.spectrum.ieee.org/WEBONLY/publicfeature/nov03/1103ebom.html].
22 Will Dunham, “U.S. May Debut Secret Microwave Weapon versus Iraq,” Reuters, Feb.
2, 2003, [http://www.globalsecurity.org/org/news/2003/030202-ebomb01.htm].
23 Victorino Matus, “Dropping the E-bomb,” The Weekly Standard, Feb. 2, 2003,

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CRS-8
Testing has been done for microwave weapons that can be used for controlling or
dispersing crowds without killing people. These types of weapons reportedly create
microwave energy of longer duration that causes a painful burning sensation on the
skin, but no long-term physical damage.24
Because instantaneous HPM energy can reflect off the ground and possibly
affect piloted aircraft above, much testing currently involves HPM devices on
Unmanned Aerial Vehicles (UAVs), and the Air Force Conventional Air-Launched
Cruise Missile system. By 2010, DOD reportedly plans to field several air-launched
UAVs using disposable and reusable HPM weapons to disrupt enemy computers.25
Capabilities of Other Nations
Reportedly, several potential U.S. adversaries, such as Russia or China, are now
capable of launching a crippling HEMP strike against the United States with a
nuclear-tipped ballistic missile, and other nations, such as North Korea, could
possibly have the capability by 2015.26 Other nations that could possibly develop a
capability for HEMP operations over the next few years include United Kingdom,
France, India, Israel, and Pakistan.
According to a recent DOD report, China is actively pursuing the development
of electromagnetic pulse weapons, and is devoting significant resources to
development of other electronic warfare systems and laser weapons. The report also
notes that China’s leaders view offensive counter space weapons and other
space-based defense systems as part of inevitable scenarios for future warfare. The
report notes that China could have 30 ICBMs capable of striking the United States
by 2005, and as many as 60 by the end of the decade. Also, China may reportedly
replace 20 of its current ICBMs with a longer-range version by the end of this
decade, or sooner.27
Vladimir Lukin, the former Soviet Ambassador to the United States, and former
Chairman of the International Affairs Committee for the Russian Parliament,
23(...continued)
[http://theweeklystandard.com/Utilities/printer_preview.asp?idArticle=2209&R=9F0C22
5C3].
24 David Ruppe, “Directed-Energy Weapons: Possible U.S. Use Against Iraq Could Threaten
International Regimes,” Global Security Newswire, Aug. 16, 2002,
[http://www.globalsecurity.org/org/news/2002/020816-dew.htm ].
25 David Fulghum and Douglas Barrie Farnboruogh, “Directed-Energy Weapon for UAV,
cruise and air-to-ground missile payloads nears production,” Aviation Week & Space
Technology, July 26, 2004, p. 34.
26 Michael Sirak, “U.S. vulnerable to EMP Attack,” Jane’s Defence Weekly, July 26, 2004,
[http://www.janes.com/defence/news/jdw/jdw040726_1_n.shtml], and House Armed
Services Committee, hearing on Commission to Assess the Threat to the United States from
Electromagnetic Pulse Attack, July 22, 2004.
27 FY04 Report to Congress on PRC Military Power, Annual Report on The Military Power
of the People’s Republic of China, [http://www.defenselink.mil/pubs/d20040528PRC.pdf].

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reportedly has stated that Russia currently has a capability to create a HEMP effect
over the United States.28 During 1962, the then Soviet Union conducted a series of
atmospheric nuclear tests and observed HEMP effects that included surge protector
burnouts, power supply breakdowns, and damage to overhead and underground
buried cables at distances of 600 kilometers. Since then, Russia has reportedly made
extensive preparations to protect their infrastructure against HEMP by hardening
both civilian and military electronic equipment, and by providing continuous training
for personnel operating these protected systems.29 Other sources have reportedly
stated that Russia may also have some of the leading physicists in the world currently
doing research on electronic warfare weapons and electromagnetic pulse effects.30
Ground Wave Emergency Network
During the Cold War, the US Military designed an innovative communications
system to relay emergency messages between strategic military areas in the
continental United States, using signals that travel by means of low frequency ground
waves — electromagnetic fields that hug the ground — rather than by radiating into
the atmosphere. The Ground Wave Emergency Network, or GWEN system, was
intended to allow continuous communications despite EMP disruptions. However,
the hardware was reportedly transistor based, leaving the system with some level of
vulnerability to EMP. In addition, the fixed locations of GWEN sites were known
to adversaries, and thus vulnerable to direct attack.31
As the Cold War ended, the U.S. military took steps to reduce its nuclear arsenal
and associated infrastructure.32 After 1998, the USAF decommissioned GWEN
assets and replaced the entire system with the Single Channel Anti-Jam Man-Portable
(SCAMP) Terminal. SCAMP uses extremely high frequency (EHF) technology, is
28 The statement was reportedly made on Apr. 30, 1999, to a U.S. Congressional delegation
that traveled to Vienna to meet with officials from the Russian Duma to discuss a framework
for a peaceful solution of the then crisis in Kosovo. Hearing before the Military Research
and Development Subcommittee of the Committee on Armed Services House of
Representatives, Oct. 7, 1999, [http://commdocs.house.gov/committees/security/-
has280010.000/has280010_0.HTM ].
29 Lowell Wood, statement before the House Research and Development Subcommittee,
hearing on EMP Threats to the U.S. Military and Civilian Infrastructure, Oct. 7, 1999.
30 Barry Crane, a physicist and former F-4 pilot now working at the Institute for Defense
Analysis, has visited Russia’s top electromagnetic pulse laboratories and design bureaus,
and has stated that many Russian electromagnetic pulse specialists may also be now
working on contract in China. Kenneth R. Timmerman, May 28, 2001, “U.S. Threatened
with EMP Attack,” Insight on the News, [http://www.insightmag.com/news/2001/05/
28/InvestigativeReport/U.Threatened.With.Emp.Attack-210973.shtml].
31 Rosalie Bertell, “Background on the HAARP Project,” Global Policy Forum, Nov. 5,
1996, [http://www.globalpolicy.org/socecon/envronmt/weapons.htm].
32 Admiral Richard W. Mies, Commander in Chief, United States Strategic Command,
statement before the Senate Armed Services Committee Strategic Subcommittee on
Command Posture, July 11, 2001, p.11, [http://www.defenselink.mil/dodgc/lrs/-
docs/test01-07-11Mies.rtf].

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CRS-10
resistant to EMP, and offers more flexibility than GWEN because the equipment is
lightweight, transportable, and interoperable with DOD satellite networks.33
Policy Analysis
Private Sector Vulnerability
What is the United States doing to protect critical infrastructure systems against
the threat of electromagnetic pulse? What is the appropriate response from the
United States to a nuclear HEMP attack, where there may be widespread damage to
electronics, but relatively little, or possibly no loss of life as a direct result? How
could the United States determine which nation launched a HEMP attack? After
experiencing a HEMP effect, the United States may retain its capability to use
strategic weapons for nuclear retaliation, but will the U.S. industrial base and critical
infrastructure be crippled and incapable of supporting a sustained military campaign?
During such time, would the United States be capable of a making an effective
response should other nations chose to make military advances in other parts of the
world?
Some assert that little has been done by the private sector to protect against the
threat from electromagnetic pulse, and that commercial electronic systems in the
United States could be severely damaged by either HEMP or smaller-scale HPM.34
Officials of several U.S. power stations and public utilities have stated that their
electrical systems currently have no protection against electromagnetic pulse.35
However, electric power and telephone utilities have been known to fail as a result
of solar storms which cause effects similar to, but less severe than HEMP from a
nuclear blast. Commercial electronic surge arresters used for lightning strikes
reportedly do not clamp fast enough to protect against the instantaneous effects of
electromagnetic pulse, and some may also not have great enough current carrying
capacity.36
Military Vulnerability
The effects of large-scale HEMP have been studied over several years by the
Defense Atomic Support Agency, the Defense Nuclear Agency, and the Defense
33 Federation of American Scientists, AN/PSC-11 Single Channel Anti-Jam Man-Portable
(SCAMP)Terminal, Mar. 2000 [http://www.fas.org/spp/military/program/com/an-psc-11
.htm].
34 House Armed Services Committee, Committee Hearing on Commission to Assess the
Threat to the United States from Electromagnetic Pulse Attack, July 22, 2004.
35 Associated Press, “Experts Cite Electromagnetic Pulse as Terrorist Threat,” Las Vegas
Review-Journal, Oct. 3, 2001.
36 Army Training Manual 5-692-2, “Maintenance of Mechanical and Electrical Equipment
at Command, Control, Communications, Computers, Intelligence, Surveillance, and
Reconnaissance (C4ISR) Facilities, HEMP Protection Systems, Apr. 15, 2001, Chapter 27,
[http://www.usace.army.mil/publications/armytm/tm5-692-2/chap27VOL-2.pdf].

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CRS-11
Special Weapons Agency, and is currently being studied by the Defense Threat
Reduction Agency (DTRA). However, the application of the results of these studies
has been uneven across military weapons and communications systems. Some
analysts state that U.S. strategic military systems (intercontinental ballistic missiles
and long-range bombers) may have strong protection against HEMP, while most U.S.
weapons systems used for the battlefield do not, and that this uneven protection is
undoubtedly known to our potential adversaries.37 Some analysts reportedly state
that limited testing has shown that modern commercial equipment may be
surprisingly resistant to the effects of electromagnetic pulse, and in addition to the
SCAMP system, some military systems using commercial equipment are retrofitted
to increase resistance to EMP.38 However, there is disagreement among observers
about whether test procedures used by the U.S. military may have been flawed,
leading to erroneous conclusions about the effects of electromagnetic pulse on
commercial electronics.39
The U.S. military has adopted a policy where possibly vulnerable commercial
electronic equipment is now used extensively in support of complex U.S. weapons
systems. For example, a large percentage of U.S. military communications during
Operation Iraqi Freedom was reportedly carried by commercial satellites, and much
military administrative information is currently routed through the civilian Internet.40
Many commercial communications satellites, particularly those in low earth orbit,
reportedly may degrade or cease to function shortly after a high altitude nuclear
explosion.41 However, some observers believe that possible HEMP and HPM
vulnerabilities of military information systems are outweighed by the benefits gained
through access to innovative technology and increased communications flexibility
that come from using state-of-the-art electronics and from maintaining connections
to the civilian Internet and satellite systems.
37 Because of the very specialized nature, strategic weapons use essentially no commercial
equipment. However, DOD increasingly uses commercial equipment in other tactical
weapons. Stanley Jakubiak and Lowell Wood, statements before the House Military
Research and Development Subcommittee, hearing on EMP Threats to the U.S. Military and
Civilian Infrastructure, Oct. 7, 1999.
38 Stanley Jakubiak, statement before the House Military Research and Development
Subcommittee, Hearing on EMP Threats to the U.S. Military and Civilian Infrastructure,
Oct. 7, 1999.
39 Lowell Wood, statement before the House Military Research and Development
Subcommittee, hearing on EMP Threats to the U.S. Military and Civilian Infrastructure,
Oct. 7, 1999; and Jack Spencer, “America’s Vulnerability to a Different Nuclear Threat: An
Electromagnetic Pulse,” The Heritage Foundation Backgrounder, No.1372, May 26, 2000,
p.6.; and Carlo Kopp, “The Electromagnetic Bomb — A Weapon of Electrical Mass
Destruction,” Air and Space Power 1993, [http://www.airpower.maxwell.af.mil/
airchronicles/kopp/apjemp.html].
40 Jefferson Morris, “DISA Chief Outlines Wartime Successes,” Federal Computer Week,
June 6, 2003; and “GAO: DOD Needs New Approach to Buying Bandwidth,” Aerospace
Daily, Dec. 12, 2003.
41 U.S. Congress, House Armed Services Committee, Hearing on Commission to Assess the
Threat to the United States from Electromagnetic Pulse Attack, July 22, 2004.

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CRS-12
New Incentive to Develop a Nuclear Capability
A single nuclear device exploded at an appropriate altitude above the
continental United States could possibly affect our industrial capacity, economic
stability, and military effectiveness. Does knowledge of this vulnerability, combined
with the proliferation of nuclear technology, provide a newer incentive for potential
adversaries to develop or acquire a nuclear weapons capability? Will countries now
view the development and acquisition of nuclear weapons, even a small arsenal, as
a strategy for cyber warfare?
During the Cold War, a HEMP attack was viewed as the first step of a nuclear
exchange involving many warheads, but the threat of mutually assured destruction
provided a lasting deterrent. Today, the proliferation of nuclear technology makes
the threat of HEMP more difficult to assess. Would the leader of a rogue state be
motivated to use a small nuclear arsenal to launch a crippling HEMP strike against
the United States, with no resulting fatalities, if it believed the U.S. would likely not
retaliate with a nuclear salvo that would destroy thousands, or millions of innocent
people? Would a HEMP strike over a disputed area during a regional conflict be
seen as a way to defeat the communications links and network centric warfare
capability of the U.S. military, and gain maximum battlefield advantage from an
existing supply of smaller nuclear warheads?42
Terrorist Use of HPM
A smaller-scale HPM weapon requires a relatively simple design, and can be
built using electrical materials and chemical explosives that are easy to obtain. It is
estimated that a limited-range suitcase-sized HPM weapon could be constructed for
much less than $2,000, and is within the capability of almost any nation, and perhaps
many terrorist organizations.43 Recently, DOD recruited a scientist to create two
small HPM weapons for testing using only commercially available electrical
components, such as ordinary spark plugs and coils. One device was developed that
could be broken down into two parcels so it could be shipped by regular mail, for
example, from one terrorist to another. The second HPM device was constructed to
fit inside a small vehicle.44 Aside from specially-trained dogs, experts reportedly say
42 Jack Spencer, “America’s Vulnerability to a Different Nuclear Threat: An
Electromagnetic Pulse,” The Heritage Foundation Backgrounder, No.1372, May 26, 2000,
p.3.
43 Some experts may disagree about whether most terrorist organizations are capable of
building an inexpensive HPM weapon powered by a flux-compression generator. Michael
Abrams, “The Dawn of the E-Bomb,” IEEE Spectrum Online, Nov. 2003,
[http://www.spectrum.ieee.org/WEBONLY/publicfeature/nov03/1103ebom.html], and Carlo
Kopp, “The Electromagnetic Bomb — A Weapon of Electrical Mass Destruction,” Air and
Space Power, 1993, [http://www.airpower.maxwell.af.mil/airchronicles/kopp/apjemp.html].
44 Kenneth R. Timmerman, “U.S. Threatened with EMP Attack,” Insight on the News, May
28, 2001, [http://www.insightmag.com/news/2001/05/28/InvestigativeReport/U.Threatened.
With.Emp.Attack-210973.shtml].

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CRS-13
there are no scientific methods that currently allow easy detection of an explosive
device hidden in a vehicle or inside a suitcase before it can explode.45
It is difficult to assess the threat of a terrorist organization possibly using a
smaller-scale HPM weapon against the United States critical infrastructure. It could
be argued that an HPM bomb by itself, may not be attractive to terrorists, because its
smaller explosion would not be violent enough, and the visible effect would not be
as dramatic as a larger, conventional bomb. Also, constructing an HPM device is
still somewhat more technically complex than constructing a conventional bomb.
However, observers have reported that the leadership of terrorist organization may
increasingly become aware of the growing advantages from an attack launched
against U.S. critical information systems. In addition, the use by a terrorist group of
a new weapon directed at U.S. information systems would attract widespread media
attention, and may motivate other rival groups to follow along a new pathway.46
Additionally, the explosives used in a smaller, or suitcase-sized HPM device
could simultaneously be used to disperse radioactive materials, making it a so-called
“dirty bomb”. This combination would offer a possible two-for-one effect, where the
dispersed radioactive materials could generate immediate near-panic, while the
HPM-damaged computers might not be noticed until days later. This potential
double effect could improve the attractiveness of using an HPM device as a terrorist
weapon.
Human Rights Objections
HEMP and HPM energy weapons primarily damage electronic systems, with
little or no direct effect on humans, however, these effects may also be difficult to
limit or control. HEMP or HPM energy fields, as they instantly spread outward, may
also affect nearby hospital equipment or personal medical devices, such as pace-
makers, and may damage critical electronic systems throughout other parts of the
surrounding civilian infrastructure. For this reason, some international human rights
organizations may object to the development and use of HEMP or HPM as weapons.
Legislative Activity
In 1997, the House National Security Committee held a hearing on the Threat
Posed by Electromagnetic Pulse (EMP) to U.S. Military Systems and Civil
Infrastructure, 47 and in 1999, the House Military Research and Development
45 Tim Starks, “High-Tech Fixes for Low-Tech Warfare, Experts Say,” CQ Homeland
Security - Technology, Aug. 3, 2004.
46 Jerrold M. Post, Kevin G. Ruby, and Eric D. Shaw, “From Car Bombs to Logic Bombs:
The Growing Threat from Information Terrorism,” Terrorism and Political Violence, vol.
12, no. 2 (summer 2000), pp.97-122.
47 U.S. Congress House National Security Committee, Threat Posed by Electromagnetic
Pulse (EMP) to U.S. Military Systems and Civil Infrastructure, No. 105-18, July 16, 1997,
(continued...)

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CRS-14
Subcommittee held a hearing on the potential threats to United States civilian and
military systems from and electromagnetic pulse attack.48
A Commission to Assess the Threat from High Altitude Electromagnetic Pulse
was established by Congress in FY2001 after several experts expressed concern that
the U.S. critical infrastructure and military were vulnerable to EMP attack.49 Seven
of the Commission members were appointed by the Secretary of Defense and two by
the Director of the Federal Emergency Management Agency. On July 22, 2004, the
Commission presented a report to the House Armed Services Committee, stating that
EMP is capable of causing catastrophe for the nation.50 However, the report, which
focuses mainly on the effects of HEMP and not necessarily on HPM, also states that
such a catastrophe can be prevented by following recommendations made by the
Commission. Testimony during the presentation raised questions, such as: (1) how
would the United States respond to a limited HEMP attack against the U.S. homeland
or against U.S. forces, where there is loss of technology, but no loss of life; (2) does
the current lack of U.S. preparedness invite adversaries to plan and attempt a HEMP
attack; and (3) are the long-term effects of a successful HEMP attack, leading to
possible widespread starvation and population reduction, potentially more
devastating to the U.S. homeland than an attack by surface nuclear weapons?
CRS Products
CRS Report RL32114. Computer Attack and Cyber Terrorism: Vulnerabilities and
Policy Issues for Congress.
CRS Report RL32411. Network Centric Warfare: Background and Oversight Issues
for Congress.
CRS Report RS21528. Terrorist ‘Dirty Bombs’: A Brief Primer.
CRS Report IB92099. Nuclear Weapons: Comprehensive Test Ban Treaty.
47(...continued)
[http://commdocs.house.gov/committees/security/has197010.000/has197010_0.HTM].
48U.S. Congress, House Armed Services Committee, Electromagnetic Pulse Threats to U.S.
Military and Civilian Infrastructure, No. 106-31, Oct. 7, 1999,
[http://www.fas.org/spp/starwars/congress/1999_h/has280010_0.htm].
49 Michael Sirak, “U.S. vulnerable to EMP Attack,” Janes’s Defence Weekly, July 26, 2004,
[http://www.janes.com/defence/news/jdw/jdw040726_1_n.shtml].
50 William Graham, et. al., Report of the Commission to Assess the Threat to the United
States from Electromagnetic Pulse Attack, Volume 1: Executive Report 2004,
[http://www.house.gov/hasc/openingstatementsandpressreleases/108thcongress/04-07-22
emp.pdf].

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