Updated December 19, 2018
Defense Primer: Ballistic Missile Defense
The United States has been developing and deploying
North Korea likely has an arsenal of hundreds of SRBMs
ballistic missile defenses (BMD) to defend against enemy
that can reach all of South Korea and perhaps dozens of
missiles continuously since the late 1940s. In the late 1960s
MRBMs (whose reliability at this point remains uncertain),
and early 1970s, the United States deployed a limited
capable of reaching Japan and U.S. bases in the region.
nuclear-tipped BMD system to protect a portion of its U.S.
North Korea is in the process of developing an ICBM
land-based nuclear ICBM (intercontinental ballistic missile)
capability that could strike the U.S. homeland with a
force in order to preserve a strategic deterrent against a
nuclear warhead. Although North Korea has conducted a
Soviet nuclear attack on the Homeland. That system
number of nuclear tests, it is unclear whether any of their
became active in 1975 but shut down in 1976 because of
ballistic missiles are armed with a nuclear warhead.
concerns over cost and effectiveness. In the FY1975
budget, the Army began funding research into hit-to-kill or
The IC assesses that Iran has the largest inventory of
kinetic energy interceptors as an alternative—the type of
ballistic missiles in the Middle East. Those missiles are
interceptor technology dominates U.S. BMD systems today.
armed with conventional warheads; Iran does not have a
nuclear weapons capability. Most of Iran’s ballistic missile
In 1983, President Reagan announced an enhanced effort
force consists of SRBMs with ranges less than 500 km,
for BMD. Since the start of the Reagan initiative in 1985,
which it views as a tactical warfighting force. Iran also has
BMD has been a key national security interest in Congress.
a growing and significant number of MRBMs capable of
It has appropriated well over $200 billion for a broad range
striking targets throughout the region, which it views as a
of research and development programs and deployment of
deterrent force. Iran does not appear to have a dedicated
BMD systems here and abroad.
ICBM program.
The Missile Defense Agency (MDA) is charged with the
Almost all of China’s SRBMs are deployed at bases
mission to develop, test, and field an integrated, layered,
opposite Taiwan. China’s MRBMs can reach U.S. bases, as
BMD system (BMDS) to defend the United States, its
well as U.S. friends and allies in the region. China’s missile
deployed forces, allies, and friends against all ranges of
forces could also target U.S. naval ships in Northeast Asia.
enemy ballistic missiles in all phases of flight. Current U.S.
Additionally, China is working on a range of technologies
policy, however, is not directed at the strategic nuclear
to attempt to counter U.S. and other countries’ BMD
deterrent forces of Russia and China. The FY2019 BMD
systems. China’s ICBM and some nuclear-armed MRBM
request is $12 billion, $10 billion of which is for MDA.
forces are intended for strategic and regional deterrence.
Ballistic Missile Threats
The Major Elements of the U.S. BMDS
After an initial powered phase of flight, a ballistic missile
The United States has deployed a global array of networked
leaves the atmosphere and follows an unpowered trajectory
ground, sea, and space-based sensors for target detection
or flight path before reentering the atmosphere toward a
and tracking, an extensive number of ground- and sea-based
predetermined target. Ballistic missiles have an effective
hit-to-kill (direct impact) and blast fragmentation warhead
range from a few hundred kilometers to more than 10,000
interceptors, and a global network of command, control,
kilometers (km). Short-range ballistic missiles (SRBMs)
and battle management capabilities to link those sensors
range from 300-1,000 km and are generally considered for
with those interceptors.
tactical military use. Medium-range ballistic missiles
(MRBMs) have a range from 1,000-5,500 km, although
Ground-based Midcourse Defense (GMD)
most are armed with conventional warheads and range less
Since 2004, the United States has deployed a force of 30
than 3,500 km. ICBMs range further than 5,500 km and are
(expanding now to 64) Ground-based Interceptors (GBI) at
generally considered as strategic deterrent forces.
Ft, Greely, Alaska and Vandenberg Air Force Base,
California. The GMD system is designed to destroy a
Most of the world’s ballistic missiles belong to the United
limited attack in space from ICBMs aimed at the United
States and its friends and allies. Russia, especially, and
States, to include from North Korea and even Iran.
China have significant numbers of ICBMs. Neither the
Although the GMD system is praised by senior military
United States nor Russia possesses any land-based ballistic
leaders and is generally viewed in successful terms, it does
missiles with maximum ranges of 500-5,500 km because of
have a somewhat mixed flight test record.
the 1987 INF (Intermediate Nuclear Forces) Treaty. The
ballistic missile threats of most concern to the United States
Terminal High Altitude Area Defense (THAAD)
today are primarily the SRBM and MRBM forces from
THAAD is a highly mobile, rapidly deployable BMD
North Korea, Iran and China, and growing North Korean
system designed to shoot down attacking short- and
ICBM capabilities.
medium-range missiles during their final or terminal phase
of flight. It is designed to provide broad area coverage
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Defense Primer: Ballistic Missile Defense
against threats to population centers and industrial
and in the Persian Gulf. Although many of the BMD
resources as well as military forces.
elements of a potential cooperative system are in place in
these regions, wariness between likely foreign partners and
THAAD was initially proposed in 1987 and its first flight
opposition from countries such as China have prevented a
test occurred in April 1995. It had a very poor test record
formal agreement and participation from going forward.
until the first successful intercept in 1999. In recent years,
THAAD’s test record has demonstrated high effectiveness
Cooperation with Israel
and reliability. Many now consider it the most advanced
Since 1986, the United States has invested significantly in
BMD system in the world. The United States plans to
Israel’s missile defense programs and systems designed to
sustain seven THAAD batteries. U.S. THAAD batteries are
protect against missile and rocket attacks. The United States
now deployed in Guam, South Korea, and the Persian Gulf.
also provided a THAAD radar to Israel in 2008.Thus far,
THAAD radars are exceptionally powerful and are
the United States has provided about $2.5 billion for Israeli
currently deployed in Turkey, Israel, and Japan. Any future
programs, which include the Arrow systems designed to
THAAD batteries produced will be for Foreign Military
counter short- and medium-range ballistic missiles, Iron
Sales.
Dome (to counter short-range rockets), and David’s Sling
(designed to counter longer range rockets).
Aegis BMD
The Aegis BMD program gives Navy Aegis cruisers and
Legislative Issues
destroyers a capability for providing regional defense
BMD has broad support across the political spectrum and
against short- and medium-range ballistic missile attacks.
within the military as evidenced by the high degree of
Under current plans, the number of BMD-capable Navy
funding support for the program regardless of which party
Aegis ships is scheduled to grow from 35 to 57 at the end of
controls the White House and Congress, especially since
FY2023. Aegis BMD ships and Aegis Ashore (land-based)
the early 2000s.
capabilities in Romania (and Poland by 2019) contribute to
NATO’s territorial defense mission. Testing results have
Where Congress has cut programs tends to fall in three
shown significant Aegis BMD capabilities.
areas: where program delays allow for opportunistic
program cuts, cuts for long-lead procurement of
Patriot Advanced Capability-3 (PAC-3)
components with still questionable test results, and newer
The Army Patriot system is the most mature element of the
programs not likely to come to fruition in the short or
BMDS. It was used in combat in the 1991 and 2003 Iraq
medium term. Congress has also thus far been unwilling to
wars and is fielded around the world by the United States
fund programs that might lead to emplacing interceptor
and many others that have purchased the system. Patriot is a
capabilities in space. But this reticence may now be
mobile, transportable system designed to defend areas such
changing as the geopolitical and space environment is
as military bases and air fields. Patriot works with THAAD
changing.
to provide an integrated and overlapping defense against
attacking missiles in their final phase of flight.
Relevant Statutes
Foreign BMD Participation
P.L. 106-38 – National Missile Defense Act of 1999.
The United States has missile defense cooperative programs
with a number of allies. MDA actively participates in
CRS Products
NATO activities to develop an integrated NATO BMD
capability. Patriot systems have been purchased by allies,
CRS In Focus IF10472, North Korea’s Nuclear and Ballistic
acquisition of THAAD is in various stages of contract
Missile Programs, by Steven A. Hildreth and Mary Beth D.
negotiation and acquisition, and countries such as Japan
Nikitin
have acquired Aegis BMD capabilities.
CRS Report R42849, Iran’s Ballistic Missile and Space Launch
Programs, by Steven A. Hildreth
European Phased Adaptive Approach (EPAA)
CRS Report RL33745, Navy Aegis Ballistic Missile Defense (BMD)
At the 2010 Lisbon Summit, NATO agreed to develop a
Program: Background and Issues for Congress, by Ronald
missile defense capability to protect NATO European
O'Rourke
populations, territory and forces against the threats posed
by the proliferation of ballistic missiles. The U.S.
CRS Report R43116, Ballistic Missile Defense in the Asia-Pacific
contribution to that NATO effort is the EPAA, which
Region: Cooperation and Opposition, by Ian E. Rinehart, Steven
includes the deployment of a THAAD radar in Turkey, the
A. Hildreth, and Susan V. Lawrence
deployment of Aegis BMD ships in Europe, and the
deployment of an Aegis Ashore in Romania. A second
Other Resources
Aegis Ashore capability is being constructed in Poland,
DOD. Ballistic Missile Defense Review (BMDR) Report. Feb. 2010.
which will complete the U.S. commitment to NATO’s
territorial defense.

Other Regional BMD Cooperative Efforts
Steven A. Hildreth, Specialist in U.S. and Foreign
Similar to the EPAA, the United States has sought since
2010 to formalize a regional cooperative BMD capability
National Security Programs
both in Northeast Asia (with Japan, Korea and Australia)
IF10541
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Defense Primer: Ballistic Missile Defense


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https://crsreports.congress.gov | IF10541 · VERSION 4 · UPDATED

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