Updated October 9, 2019
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 hypersonic and ballistic missiles in all phases of
Additionally, China is working on a range of technologies
flight. Current U.S. policy, however, is not directed at the
to attempt to counter U.S. and other countries’ BMD
strategic nuclear deterrent forces of Russia and China. The
systems. China’s ICBM and some nuclear-armed MRBM
FY2020 budget request is $13.6 billion for missile defense,
forces are intended for strategic and regional deterrence.
$9.4 billion of which is for MDA.
The Major Elements of the U.S. BMDS
Ballistic Missile Threats
The United States has deployed a global array of networked
After an initial powered phase of flight, a ballistic missile
ground, sea, and space-based sensors for target detection
leaves the atmosphere and follows an unpowered trajectory
and tracking, an extensive number of ground- and sea-based
or flight path before reentering the atmosphere toward a
hit-to-kill (direct impact) and blast fragmentation warhead
predetermined target. Ballistic missiles have an effective
interceptors, and a global network of command, control,
range from a few hundred kilometers to more than 10,000
and battle management capabilities to link those sensors
kilometers (km). Short-range ballistic missiles (SRBMs)
with those interceptors.
range from 300-1,000 km and are generally considered for
tactical military use. Medium-range ballistic missiles
Ground-based Midcourse Defense (GMD)
(MRBMs) have a range from 1,000-5,500 km, although
Since 2004, the United States has deployed a force of 44
most are armed with conventional warheads and range less
(expanding now to 64) Ground-based Interceptors (GBI) at
than 3,500 km. ICBMs range further than 5,500 km and are
Ft, Greely, Alaska and Vandenberg Air Force Base,
generally considered as strategic deterrent forces.
California. The GMD system is designed to destroy a
limited attack in space from ICBMs aimed at the United
Most of the world’s ballistic missiles belong to the United
States, to include from North Korea and even Iran.
States and its friends and allies. Russia, especially, and
Although the GMD system is praised by senior military
China have significant numbers of ICBMs. Russia
leaders and is generally viewed in successful terms, it does
continues to possess intermediate-range ballistic cruise
have a somewhat mixed flight test record.
missiles (3,500-5,500 km), which led to the U.S.
withdrawal from the 1987 INF (Intermediate Nuclear
Terminal High Altitude Area Defense (THAAD)
Forces) Treaty. The ballistic missile threats of most concern
THAAD is a highly mobile, rapidly deployable BMD
to the United States today are primarily the SRBM and
system designed to shoot down attacking short- and
MRBM forces from North Korea, Iran and China, and
medium-range missiles during their final or terminal phase
growing North Korean ICBM capabilities.
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
Other Regional BMD Cooperative Efforts
resources as well as military forces.
Similar to the EPAA, the United States has sought since
2010 to formalize a regional cooperative BMD capability
THAAD was initially proposed in 1987 and its first flight
both in Northeast Asia (with Japan, Korea and Australia)
test occurred in April 1995. It had a very poor test record
and in the Persian Gulf. Although many of the BMD
until the first successful intercept in 1999. In recent years,
elements of a potential cooperative system are in place in
THAAD’s test record has demonstrated high effectiveness
these regions, wariness between likely foreign partners and
and reliability. Many now consider it the most advanced
opposition from countries such as China have prevented a
BMD system in the world. The United States has delivered
formal agreement and participation from going forward.
seven THAAD batteries to the U.S. Army. U.S. THAAD
batteries are now deployed in Guam, South Korea, and the
Cooperation with Israel
Persian Gulf. THAAD radars are exceptionally powerful
Since 1986, the United States has invested significantly in
and are currently deployed in Turkey, Israel, and Japan.
Israel’s missile defense programs and systems designed to
Any future THAAD batteries produced will be for Foreign
protect against missile and rocket attacks. The United States
Military Sales.
also provided a THAAD radar to Israel in 2008.Thus far,
the United States has provided about $2.5 billion for Israeli
Aegis BMD
programs, which include the Arrow systems designed to
The Aegis BMD program gives Navy Aegis cruisers and
counter short- and medium-range ballistic missiles, Iron
destroyers a capability for providing regional defense
Dome (to counter short-range rockets), and David’s Sling
against short- and medium-range ballistic missile attacks.
(designed to counter longer range rockets).
Under the FY2020 budget submission, the number of
BMD-capable Navy Aegis ships is projected to increase
Legislative Issues
from 38 to 59 at the end of FY2024. Aegis BMD ships and
BMD has broad support across the political spectrum and
Aegis Ashore (land-based) capabilities in Romania (and
within the military as evidenced by the high degree of
Poland by 2020) contribute to NATO’s territorial defense
funding support for the program regardless of which party
mission. Testing results have shown significant Aegis BMD
controls the White House and Congress, especially since
capabilities.
the early 2000s.
Patriot Advanced Capability-3 (PAC-3)
Where Congress has cut programs tends to fall in three
The Army Patriot system is the most mature element of the
areas: where program delays allow for opportunistic
BMDS. It was used in combat in the 1991 and 2003 Iraq
program cuts, cuts for long-lead procurement of
wars and is fielded around the world by the United States
components with still questionable test results, and newer
and many others that have purchased the system. Patriot is a
programs not likely to come to fruition in the short or
mobile, transportable system designed to defend areas such
medium term. Congress has also thus far been unwilling to
as military bases and air fields. Patriot works with THAAD
fund programs that might lead to emplacing interceptor
to provide an integrated and overlapping defense against
capabilities in space. But this reticence may now be
attacking missiles in their final phase of flight.
changing as the geopolitical and space domain is changing.
Foreign BMD Participation
Relevant Statutes
The United States has missile defense cooperative programs
P.L. 106-38 – National Missile Defense Act of 1999.
with multiple allies. MDA actively participates in NATO
activities to develop an integrated NATO BMD capability.
Patriot systems have been purchased by allies, acquisition
CRS Products
of THAAD is in various stages of contract negotiation and
CRS In Focus IF10472, North Korea’s Nuclear and Ballistic
acquisition, and countries such as Japan have acquired
Missile Programs, by Steven A. Hildreth and Mary Beth D.
Aegis BMD capabilities. The Kingdom of Saudi Arabia
Nikitin
(KSA) is on contract to receive seven THAAD batteries.
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
CRS Report R43116, Ballistic Missile Defense in the Asia-Pacific
by the proliferation of ballistic missiles. The U.S.
Region: Cooperation and Opposition, by Ian E. Rinehart, Steven
contribution to that NATO effort is the EPAA, which
A. Hildreth, and Susan V. Lawrence
includes the deployment of a THAAD radar in Turkey, the
deployment of Aegis BMD ships in Europe, and the
Other Resources
deployment of an Aegis Ashore in Romania. A second
DOD. 2019 Missile Defense Review. Jan. 2019.
Aegis Ashore capability is being constructed in Poland,
which will complete the U.S. commitment to NATO’s

territorial defense.
Stephen M. McCall, Analyst in Military Space, Missile
Defense, and Defense Innovation
IF10541
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Defense Primer: Ballistic Missile Defense


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https://crsreports.congress.gov | IF10541 · VERSION 6 · UPDATED

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