Updated November 23, 2022
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 has flight-tested two types of road-mobile
land-based nuclear ICBM (intercontinental ballistic missile)
ICBMs that have the range to strike the U.S. homeland. The
force in order to preserve a strategic deterrent against a
Defense Intelligence Agency (DIA) has assessed that
Soviet nuclear attack on the Homeland. That system
“North Korea’s continued development of ICBMs, IRBMs,
became active in 1975 but shut down in 1976 because of
and [submarine-launched ballistic missiles] demonstrates its
concerns over cost and effectiveness. In the FY1975
intention to bolster its nuclear delivery capability.”
budget, the Army began funding research into hit-to-kill or
kinetic energy interceptors as an alternative—the type of
The intelligence community assesses that Iran has the
interceptor technology that dominates U.S. BMD systems
largest inventory of ballistic missiles in the Middle East.
today.
Those missiles are armed with conventional warheads; Iran
does not have a nuclear weapons capability. Most of Iran’s
In 1983, President Reagan announced an enhanced effort
ballistic missile force consists of SRBMs with ranges less
for BMD. Since the start of the Reagan initiative in 1985,
than 500 km, which it views as a tactical warfighting force.
BMD has been a key national security interest in Congress,
Iran also has a growing and significant number of MRBMs
which has appropriated well over $200 billion for a broad
capable of striking targets throughout the region, which it
range of BMD research and development programs and
views as a deterrent force. Iran does not appear to have a
deployment of BMD systems here and abroad.
dedicated 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, U.S.
well as U.S. allies and partners in the region. China’s
deployed forces, and U.S. allies and partners against
missile forces could also target U.S. naval ships in
ballistic missiles of all ranges and in all phases of flight.
Northeast Asia. Additionally, China is working on a range
The FY2023 budget request is $24.7 billion for missile
of technologies to attempt to counter U.S. and other
defense, $9.6 billion of which is for MDA.
countries’ BMD systems. China’s ICBM and some nuclear-
armed MRBM forces are intended for strategic and regional
Ballistic Missile Threats
deterrence.
After an initial powered phase of flight, a ballistic missile
leaves the atmosphere and follows an unpowered trajectory
The Major Elements of the U.S. BMDS
or flight path before reentering the atmosphere toward a
The United States has deployed a global array of networked
predetermined target. Ballistic missiles have an effective
ground, sea, and space-based sensors for target detection
range from a few hundred kilometers (km) to more than
and tracking, an extensive number of ground- and sea-based
10,000 km. Short-range ballistic missiles (SRBMs) range
hit-to-kill (direct impact) and blast fragmentation warhead
from 300-1,000 km and are generally considered for tactical
interceptors, and a global network of command, control,
military use. Medium-range ballistic missiles (MRBMs)
and battle management capabilities to link those sensors
have a range from 1,000-5,500 km, although most are
with those interceptors.
armed with conventional warheads and range less than
3,500 km. ICBMs range further than 5,500 km and are
Ground-Based Midcourse Defense (GMD)
generally considered as strategic deterrent forces.
Since 2004, the United States has deployed a force of 44
(expanding now to 64) Ground-based Interceptors (GBI) at
Most of the world’s ballistic missiles belong to the United
Fort Greely, AK, and Vandenberg Air Force Base, CA. The
States and its allies and partners; however, China and, in
GMD system is designed to destroy a limited attack in
particular, Russia also have significant numbers of ICBMs.
space from ICBMs aimed at the United States, to include
Russia continues to possess intermediate-range ballistic and
from North Korea and Iran. Although the GMD system has
cruise missiles (3,500-5,500 km), which led to the U.S.
been praised by senior military leaders, it does have a
withdrawal from the 1987 Intermediate Nuclear Forces
somewhat mixed flight test record, having failed 8 out of 18
(INF) Treaty. The 2022 Missile Defense Review
intercept attempts between 1999 and 2018.
additionally identifies ballistic missile threats from North
Korea and Iran.
Terminal High Altitude Area Defense (THAAD)
THAAD is a highly mobile, rapidly deployable BMD
system designed to shoot down incoming short- and
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Defense Primer: Ballistic Missile Defense
medium-range missiles during their final or terminal phase
Other Regional BMD Cooperative Efforts
of flight. It is designed to provide broad area coverage
Similar to the EPAA, the United States has sought since
against threats to population centers and industrial
2010 to formalize a regional cooperative BMD capability
resources as well as military forces.
both in Northeast Asia (with Japan, Korea, and Australia)
and in the Persian Gulf. Although many of the BMD
THAAD was initially proposed in 1987 and its first flight
elements of a potential cooperative system are in place in
test occurred in April 1995. It had a very poor test record—
these regions, wariness between likely foreign partners and
failing its first six flight tests—until the first successful
opposition from countries such as China have prevented a
intercept in 1999, following the program’s restructuring. In
formal agreement and participation from going forward.
recent years, THAAD’s test record has demonstrated high
effectiveness and reliability, succeeding in 15 out of 15
Cooperation with Israel
intercept attempts between 1999 and 2018. Many now
Since 1986, the United States has invested significantly in
consider it the most advanced BMD system in the world.
Israel’s missile defense programs and systems designed to
The United States has delivered seven THAAD batteries to
protect against missile and rocket attacks. The United States
the U.S. Army. U.S. THAAD batteries are now deployed in
also provided a THAAD radar to Israel in 2008. Between
Guam, South Korea, and the Persian Gulf. THAAD radars
FY2006 and FY2021, the United States provided about $7.6
are exceptionally powerful and are currently deployed in
billion for Israeli BMD programs, which include the Arrow
Turkey, Israel, and Japan. Any future THAAD batteries
systems designed to counter short- and medium-range
produced will be for Foreign Military Sales.
ballistic missiles, Iron Dome (to counter short-range
rockets), and David’s Sling (designed to counter longer-
Aegis BMD
range rockets).
The Aegis BMD program gives Navy Aegis cruisers and
destroyers a capability for providing regional defense
Legislative Issues
against short- and medium-range ballistic missile attacks.
BMD has broad support across the political spectrum and
Under the FY2023 budget submission, the number of
within the military as evidenced by the high degree of
BMD-capable Navy Aegis ships is projected to increase
funding support for the program regardless of which party
from 44 to 50 at the end of FY2023. Aegis BMD ships and
controls the White House and Congress, especially since
Aegis Ashore (land-based) capabilities in Romania (and
the early 2000s.
Poland by 2023) contribute to NATO’s territorial defense
mission. Aegis BMD succeeded in 40 out of 49 intercept
Where Congress has cut programs tends to fall in three
attempts between 1999 and 2018.
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.
mobile, transportable system designed to defend areas such
CRS Products
as military bases and air fields from advanced aircraft,
CRS In Focus IF10472, North Korea’s Nuclear Weapons and
cruise missiles, and tactical ballistic missiles. Patriot works
Missile Programs, by Mary Beth D. Nikitin and Samuel D.
with THAAD to provide an integrated and overlapping
Ryder.
defense against attacking missiles in their final phase of
CRS Report R42849, Iran’s Ballistic Missile and Space Launch
flight.
Programs, by Steven A. Hildreth.
Foreign BMD Participation
CRS Report RL33745, Navy Aegis Ballistic Missile Defense (BMD)
Program: Background and Issues for Congress, by Ronald
The United States has missile defense cooperative programs
O'Rourke.
with multiple allies. MDA actively participates in NATO
activities to develop an integrated NATO BMD capability.
Other Resources
Patriot systems have been purchased by allies, acquisition
Defense Department. 2022 Missile Defense Review. October
of THAAD is in various stages of contract negotiation and
2022.
acquisition, and countries such as Japan have acquired
Aegis BMD capabilities. The Kingdom of Saudi Arabia is
on contract to receive seven THAAD batteries.
This In Focus was initially authored by Stephen M. McCall,
former Analyst in Military Space, Missile Defense, and
European Phased Adaptive Approach (EPAA)
Defense Innovation.
At the 2010 Lisbon Summit, NATO agreed to develop a
missile defense capability to protect European NATO
Kelley M. Sayler, Coordinator, Analyst in Advanced
populations, territory, and forces against the threats posed
Technology and Global Security
by the proliferation of ballistic missiles. The U.S.
IF10541
contribution to that NATO effort is the EPAA, which
includes the deployment of a THAAD radar in Turkey,
Aegis BMD ships in Europe, and Aegis Ashore in Romania
and Poland.
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Defense Primer: Ballistic Missile Defense


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