A Look at National Missile Defense and the Ground-Based Midcourse Defense System

A Look at National Missile Defense and the Ground-Based Midcourse Defense System

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Nathan Voegeli

The James Martin Center for Nonproliferation Studies

Political Evolution of National Missile Defense

The United States has shown interest in developing a national missile defense since the 1950s. By the middle of the 1960s the United States was actively developing the Sentinel missile defense system.[1] This system was designed to protect a number of U.S. cities from a missile attack from the Soviet Union. After China detonated its first nuclear weapon in June 1967, Sentinel was reoriented towards a small scale Chinese attack. The system was planned to provide both a short- and long-range defense using nuclear-tipped interceptor missiles. Once the interceptor got within range of the offensive missiles, it would detonate a nuclear explosion, releasing X-rays that would destroy the attacking warheads. This program was postponed in January 1969 by the Nixon administration, which advocated Safeguard, a new variation on missile defense. Safeguard differed from Sentinel in that it was designed not to protect U.S. cities, but a battery of Minuteman intercontinental ballistic missiles (ICBMs) located in North Dakota. The Senate approved construction of the first Safeguard site in August 1969. On October 1, 1975, Safeguard became the first operationally deployed missile defense system in the United States, but it was deemed militarily ineffective by Congress the following day. One issue contributing to the decommissioning by Congress was the altered security environment in which the United States and Soviet Union found themselves at the time.

In an effort to guarantee that both countries would experience an unimaginable level of destruction in a nuclear exchange and to prevent an arms race in anti-ballistic missile systems that might jeopardize their nuclear deterrents, the Anti-Ballistic Missile (ABM) Treaty was concluded between the Soviet Union and the United States in 1972.[2] This treaty effectively limited the missile defense possibilities available. The two sides were allowed to deploy ABM systems capable of protecting two sites, the capital and one battery of nuclear-tipped ICBMs. However, these two sites had to be sufficiently distant from each other to prohibit the possibility of a regional missile defense system. The ABM Treaty further prohibited deployment of the infrastructure for a regional defense system, including a nationwide system, and testing, development, and deployment of a sea-, air-, space, or mobile land-based system. Recognizing that the security climate could continue to change, the ABM Treaty contained a clause that would allow withdrawal from the treaty if "extraordinary events" related to ABM systems and their deployment jeopardized the greater interests of the Soviet Union or the United States.

The Strategic Defense Initiative (SDI) was established in the early 1980s and researched the viability of a non-nuclear missile defense system. SDI, also known as the Star Wars program, was intended to shift the nuclear strategic security focus from a retaliatory attack to a defensive deterrent. This program laid much of the technological foundation for the current missile defense development. However, it was necessarily limited in scope because of the restrictions found in the ABM Treaty.

After the collapse of the Soviet Union and the end of the Cold War, there was renewed U.S. interest in deploying a national defense against a limited ballistic missile attack. As relations with Washington improved, Russia was no longer considered the nuclear threat that the Soviet Union presented, arguably making the ABM Treaty no longer relevant. Also, there were concerns of additional states considered hostile by the United States developing ICBMs. Starting in the early 1990s, the political climate in Washington steadily warmed to a regional missile defense system, which would protect a large area of the United States, but was prohibited by the ABM Treaty. This interest led to increased studies on the feasibility of a regional defense and steps to develop relevant technologies.

In 1998 the Department of Defense awarded Boeing a $1.6 billion contract for the national missile defense (NMD) system, the official start of the current missile defense program.[3] The intent of the contract was to allow Boeing to develop the Ground-Based Interceptor (GBI) and other component systems in order to demonstrate NMD system capabilities. Based on its performance, a decision could then be made regarding whether or not NMD would be deployed. This decision was to be based on four criteria: the ICBM threat to the United States, the technical capabilities of the system, the environmental impact, and the projected cost. Based on questions of its technical capabilities, in September 2000 the Clinton administration chose to postpone the final decision on NMD deployment, leaving it to the Bush administration.

The Bush administration gave notice of its planned withdrawal from the ABM Treaty in December 2001, effective June 2002, due to a "profoundly different" atmosphere of security.[4] Threats from "weapons of mass destruction and their delivery means wielded by terrorists and rogue states" were primary concerns in the new security environment.[5]

In January 2002 the Ballistic Missile Defense Organization, which was a new name for the SDI Organization originally established in 1983, was itself renamed the Missile Defense Agency (MDA). Despite the name changes the organization continues its oversight of a variety of missile defense programs with the goal of developing a non-nuclear missile defense. MDA has been funded at a level over $7 billion per year since fiscal year 2002, and over $3 billion has been allocated for the midcourse intercept program alone in fiscal year 2006. While the system cost for midcourse defense is not currently available, the life-cycle expense through FY2026 was estimated to be $44.5 billion by the Clinton administration.[6]

Groundbreaking for the Ft. Greely, Alaska, interceptor site took place in June 2002 and the first interceptor was installed July 22, 2004.

What is NMD?

Missile defense is based on the idea that ICBMs can be intercepted and destroyed along the trajectory to their target. There are three distinct stages of ICBMs–the boost, midcourse, and terminal phases. The boost phase consists of liftoff and powered flight of the rocket out of the atmosphere. The warhead then separates from the booster and continues on an exoatmospheric trajectory, where atmospheric drag is minimal, towards its target during the midcourse phase. After re-entering the atmosphere, the warhead follows its trajectory in a freefall towards the target. This is the terminal phase. The midcourse phase is by far the longest in duration, lasting approximately 20 minutes.

The ballistic missile defense system, which addresses all of these phases, is referred to as a layered defense. This type of defense is able to provide distinct layers, or systems, that address the specific problems encountered in each phase of ICBM flight. The concept underlying this approach is that multiplicity of the systems should provide more chances for a successful kill of the warhead.

The United States is currently developing systems for each stage of flight, such as the Airborne Laser for the boost phase, and the Patriot Advanced Capability-3 (PAC-3) system as a terminal phase defense. The mid-course phase intercept program, which included the GBI system, and NMD were used interchangeably by the Clinton administration. In 2002 NMD was changed to the Ground-Based Midcourse Defense (GMD) program. (NMD and GMD will be used interchangeably throughout this brief.)

During the midcourse phase of its flight, a warhead is not powered, but falls through space along a predetermined path. GMD attempts to counter this type of attack with the launch of interceptor missiles, which include a kill vehicle as their payload. Once set on a general intercept trajectory for the warhead, the exoatmospheric kill vehicle (EKV), which is able to provide powered corrections to its flight path, drives itself into the offensive warhead. The resulting collision is supposed to destroy both the warhead and the EKV. This interception process has proven to be a technological challenge involving a large amount of interaction and coordination between radar systems, control systems, the interceptor rocket, and the EKV.

Why Develop and Deploy GMD?

There are several reasons for developing a midcourse defense. Perhaps the most commonly cited is the threat of rogue states. Rogue states, sometimes specified as North Korea or Iran, could develop or acquire ICBM capabilities. A commission assessing the ballistic missile threat to the United States (chaired by Donald Rumsfeld and therefore referred to as the Rumsfeld Commission) reported to Congress in July 1998 that ballistic missiles could be deployed with virtually no advanced warning for the United States.[7] Clarifying their March 1998 annual report and the update memorandum released in October of the same year, an unclassified estimate by the National Intelligence Council (NIC) in 1999 expressed confidence that the intelligence community could predict development of ICBMs, but not necessarily their performance.[8] These findings represented a new sense of vulnerability to an ICBM attack for which the United States had no effective national defense. The Rumsfeld Commission recommended that U.S. policies and practices be revised to reflect this new reality.[9] Development and activation of NMD was advocated in order to protect the United States as soon as possible, given that there may be no warning of a nation's ability to deploy ICBMs.

Another concern raised by the Rumsfeld Commission is that the political decision-making of rogue states cannot be predicted, nor can a development pattern be identified for these missile programs.[10] The United States, it is argued, can no longer rely on a set pattern of testing before a system is deployed. It is possible, and indeed has happened because of the international exchange of technology, for a country to develop and deploy a ballistic missile system after a single successful test flight.[11] This being the case, there might not be enough time for the United States to deploy an NMD capability after learning of a missile test flight. According to NMD proponents, the United States would be left vulnerable to a missile threat while playing catch-up on a defense against such a risk.

The United States is also vulnerable to an unauthorized or accidental launch of an ICBM or ICBMs from Russia in the absence of an NMD shield. While it is generally acknowledged that there is no longer an immediate threat from a massive intentional ICBM launch by Russia, there remains great concern about the possibility of an unintentional or accidental launch.[12] Most scenarios predict a limited number of ICBMs being launched at the United States due to Russian missile early warning and command and control problems. Possibilities could include mistaking a U.S. test launch for an attack, a simple software problem that incorrectly indicates a U.S. attack, or a rogue Russian commander. In theory, NMD would have the capability to protect against most, if not all, of the incoming missiles, thereby eliminating, or at least mitigating, the devastation that would otherwise fall on the United States.

As China continues to develop, increase its regional influence, and expand its nuclear arsenal, it could present a more substantial ICBM threat to the United States than it has in the past.[13] China currently has a rather small ICBM arsenal (estimated to be around 30) of missiles capable of reaching the United States. NMD diminishes the threat these missiles would pose to the United States if China were to become hostile. Uncertainty about the future of China and the situation with Taiwan make it prudent, according to some advocates, for the United States to develop the technologies necessary for its own protection. The United States has long supported autonomy for Taiwan and has planned to protect it in case of aggression from mainland China.

If a rogue state developed an ICBM capability from which the United States has no defense, advocates fear the political repercussions that could result. These can be summarized in three words: deter, constrain, and harm. These potentialities are generally acknowledged in the NIC report, the report of the Rumsfeld Commission, and expressed by Senator Jeff Sessions, chairman of the Strategic Forces Subcommittee of the Senate Armed Services Committee.[14] ICBMs could be used to deter the United States from becoming involved in regional conflicts, or lessen the extent to which Washington would be willing to involve itself. Being held hostage to the ICBM threat could constrain U.S. policy alternatives. If the United States was not intimidated and did decide to become involved in a regional conflict, ICBMs could present a viable means to exploit the U.S. vulnerability to missile attack and inflict considerable harm on the United States or its forces. This introduces even more uncertainty into U.S. policy making, which would now have to decide whether U.S. interests in a region are worth the risk posed by an ICBM attack on the United States. Advocates argue that without an NMD capability, U.S. foreign policy would be subject to the threats and intimidation of any country with an ICBM, even if these threats were never made explicit. Uncertainty about the reaction of an ICBM-capable country could limit U.S. involvement in regional affairs.

Given the end of the Cold War and the proliferation of missile and weapons of mass destruction (WMD) technology since that time, the United States is confronted with the fact that these programs are a political outgrowth of the fundamental interest some states have in acquiring these technologies.[15] Nonproliferation efforts are unlikely to be effective in the future, just as they failed to prevent India and Pakistan from conducting nuclear and ballistic missile tests. The Rumsfeld Commission notes that these tests are not a singular failure, but could be considered the future norm.[16] This new reality allowed Lieutenant General Henry Obering, director of the MDA, to proclaim "…let's face it, we are the ultimate in arms control."[17] Fielding a functional, continually evolving NMD capability projects strength and, it is argued, would encourage arms control, since strength discourages other countries from investing in WMD technology. If arms control did fail, however, GMD gives the United States a last defense against ICBMs.

Finally, advocates such as Senator Sessions point out that any defense against ICBMs is better than no defense.[18] If there is no protection from ICBMs, then there is no chance that the United States can protect itself from an attack. Any NMD capability that the United States can put into operation, whether it has a "better-than-zero" or "much, much better than zero" chance at intercepting an ICBM, is an improvement over the alternative.[19]


Technological Inabilities

The issue of NMD remains a point of contention and there are several concerns expressed by those who oppose the current NMD system. Frequently, NMD is criticized as being ineffective due to technological reasons, which include the inability to overcome countermeasures, inability to defend against a chemical or biological weapon delivered by ballistic missile, uncertainty due to lack of testing for interceptors, and uncertainty due to testing that is considered biased.

The NIC report stated that a country capable of fielding an ICBM would be capable of developing countermeasures.[20] A Union of Concerned Scientists/ Massachusetts Institute of Technology (UCS/MIT) report that focused on relatively unsophisticated countermeasures concluded that these countermeasures would have a significant impact on the effectiveness of GMD.[21] Rather than focusing on making decoys resemble a warhead, they considered countermeasures that would disguise the warhead to make it look like a decoy, which would be a simpler prospect. Also, the warhead could be covered in a liquid nitrogen-cooled metal shroud, which would make it more difficult for the EKV to find the warhead in time to maneuver into its path. These two types of countermeasures require the EKV to be highly proficient at not only detecting a warhead, which may be disguised or hidden, but also distinguishing it from decoys that are specifically designed to fool it.

If the EKV is designed to address only some of these countermeasures, then, opponents argue, GMD remains vulnerable. Indeed, NMD must take into account all possible countermeasures that could be developed and deployed on an ICBM.[22] The entire system will remain vulnerable to a missile attack unless it can guarantee that any conceivable countermeasure that could be developed can be successfully distinguished and overcome by the EKV. It becomes a question of whether the United States can feasibly develop a system that must be deployed prior to an attack, therefore leaving it vulnerable to countermeasures that are specifically designed to overcome it.

The effectiveness of NMD to defend against missile launches by Russia or China is argued to be null.[23] Russia has indicated it will deploy countermeasures to overcome NMD, thereby thwarting its effectiveness against an unintentional or unauthorized Russian launch mentioned by advocates. Similarly, China is assumed to have many countermeasures available that would decrease the effectiveness of GMD.

The UCS/MIT report further argues that NMD is incapable of guarding against a biological or chemical weapon ballistic missile attack.[24] The reason for this is due to the difference in delivery between these types of weapons and a nuclear weapon. Whereas a nuclear warhead is a single unit, biological and chemical weapons would more effectively be distributed in the form of tens or hundreds of bomblets, a possibility recognized by the Rumsfeld Commission.[25] Once the booster has burned out, these bomblets would be released, effectively forming a crowd of projectiles. Each bomblet would have a separate trajectory ensuring that the agent would be spread over a greater area. The likelihood NMD could intercept all of them would be very low. Even if only one ICBM was launched with this configuration, there are only enough interceptors available to destroy a small fraction of the bomblets.

A 2005 GAO report covering missile defense raises concerns about the performance of GMD.[26] The report finds that tests conducted as part of GMD demonstrate that the system is basically functional. Five of 10 total tests since 1999 have resulted in successful intercepts according to the MDA, though the final two failures were a result of the booster failing to launch. The GAO report points out that while these five tests were successful, they used artificial means, such as the use of GPS on the reentry vehicle and hardware and software that are not the same as those used in the deployed NMD system.[27] There are still questions of whether the interceptors installed at Ft. Greely will perform successfully with the EKV since these two systems have never been tested together. The report concludes that while components have met their individual testing requirements, this is no guarantee that the complete system will perform effectively.[28]

The last two tests conducted in December 2004 and February 2005 do not prove that a warhead cannot be intercepted, but they do indicate that complex systems can be thwarted by simple problems. According to General Obering, the boosters failed to launch due to a software problem and a corroded hinge, respectively.[29] It is reasonable to assume that a fully integrated system may present similar "technical glitches," which, while relatively minor, have profound effects on the effectiveness of an intercept attempt. The more complex the system, the more difficult it becomes to anticipate all potential problems, major and minor, that could result in a failure of the system.

Political Realities

Critics of NMD often point out that the United States is much more likely to face a threat from much simpler delivery methods, a threat that is not addressed by NMD, and advocate directing funds to thwart these attacks rather than a potential ICBM attack. There are several alternative threats acknowledged by the NIC report, which admittedly lack the prestige and coercive diplomacy concurrent with recognized ICBM capabilities.[30] Relatively simple means of weapon delivery, such as the use of a ship or truck to transport a crude nuclear weapon, would be cheaper, more covert, more reliable, more accurate, and completely avoid missile defense systems.

The fielding of an NMD system, it is feared by opponents, will lead to another arms race. In the case of China, for example, it could force China to develop larger missile forces and better countermeasures to maintain its perceived threat to the United States. Just as the United States and Russia relied on their nuclear arsenals to temper each other's international ambitions, China has an incentive to maintain U.S. susceptibility to an ICBM attack in order to develop and maintain regional superiority. The UCS/MIT report proposes cooperation as the best way to meet the missile threats from Russia and China.[31] NMD could decrease the effectiveness of nonproliferation regimes, and increase U.S. vulnerability to WMD attacks.

Fielding NMD would alter not just the way other countries relate to the United States, but it undoubtedly would have effects on how the United States relates to the rest of the world. If U.S. politicians believe that they have an effective shield against an ICBM attack, it could be manifest in their actions. This could cause the United States to treat a rogue state or regional crisis with less tact than is due the situation. The United States may react much more belligerently if it believes it has a credible defense against ICBMs than it would if it had no defense. As discussed earlier, those in favor of NMD argue that the United States should have protection from being constrained or deterred in its policy goals. Rather than treating the crisis with the consideration it would require, the United States may actually aggravate the situation by ignoring the core issues and choose instead to rely on its perceived ability to defend against an ICBM attack.


Debate over GMD remains even as the system is being deployed. Advocates view it as a legitimate and effective defense against missile attacks from rogue states, as well as ensuring that the United States will not be deterred, harmed, or constrained by an ICBM threat. Even if it were assumed that GMD will continue to develop and pass the tests designed for it, there remain many issues of concern for opponents. GMD as a defensive weapon must overcome much more complex problems than any attacking force would have to overcome. Countermeasures designed specifically to penetrate GMD, questions of test design, reliability of the entire NMD system, and inherent difficulties with complex systems present continuous and evolving technological challenges. Additionally, there are political concerns regarding possible alternative delivery methods, the effect on nonproliferation regimes, and the diplomatic consequences of fielding an NMD system. One thing is certain, the political challenges presented by GMD, one of the most sophisticated projects ever, are no less daunting than the technological challenges.


WMD411: Ballistic Missile Defense,


[1] The background information on the Sentinel and Safeguard missile defense systems have been drawn largely from information found on the project website of the Claremont Institute,
[2] US Department of State, "Treaty Between the United States of America and the Union of Soviet Socialist Republics on the Limitation of Anti-Ballistic Missile Systems," May 26, 1972, TIAS no. 8276,
[3] Boeing, Press Release, April 30, 1998, "Boeing Wins $1.6 Billion-Dollar Contract from DoD's Joint Program Office to Act as Lead System Integrator for National Missile Defense Program,"
[4] Office of the Press Secretary, ABM Treaty Fact Sheet, Statement by the White House Press Secretary, December 13, 2001, "Announcement of Withdrawal from the ABM Treaty,"
[6] Budget information gathered from the following sources: Library of Congress, Congressional Research Service, Stephen A. Hildreth, coord., Missile Defense: The Current Debate, RL3111, July 19, 2005; United States Diplomatic Mission to Italy,; Missile Defense Agency, "Historical funding for MDA FY85-05," Missile Defense Agency,
[7] House Armed Services Committee, Commission to Assess the Ballistic Missile Threat to the United States, Donald H. Rumsfeld et al., Report of the Commission to Assess the Ballistic Missile Threat to the United States, 104th Congress, July 15, 1998, p. 13, (Hereafter Rumsfeld Commission)
[8] Central Intelligence Agency, National Intelligence Council, Foreign Missile Developments and the Ballistic Missile Threat to the United States Through 2015, National Intelligence Council, (Hereafter NIC report)
[9] Rumsfeld Commission, p. 16.
[10] Ibid., p. 13.
[11] Ibid., p. 14.
[12] Ibid., p. 5.
[13] Ibid., p. 6.
[14] NIC report; Rumsfeld Commission, p. 5; Jeff Sessions, "Missile Defense: Long Way in a Short Time," Military Aerospace Technology 4 (August 5, 2005),
[15] Rumsfeld Commission, p. 11.
[16] Ibid.
[17] Wade Boese and Miles A. Pomper, "Defending Missile Defense: An Interview with Missile Defense Agency Director Lt. Gen. Henry Obering," Arms Control Today 35 (November 2005), (Hereafter Obering interview)
[18] Sessions.
[19] General Obering has stated the missile defense capabilities in such terms, citing the classified nature of the exact percentage effectiveness. See Obering interview.
[20] NIC report.
[21] Union of Concerned Scientists/Massachusetts Institute of Technology Security Studies Program, Andrew M. Sessler et al., Countermeasures: A Technological Evaluation of the Operational Effectiveness of the Planned US National Missile Defense System, April 2000, p. xxi, (Herafter UCS/MIT report)
[22] Ibid., p. xxii.
[23] Ibid., p. xxii.
[24] Ibid., p. xxi.
[25] Rumsfeld Commission, p. 4.
[26] US Government Accountability Office, Defense Acquisitions: Status of Ballistic Missile Defense Program in 2004, GAO-05-243, March 2005, p. 85, (Hereafter GAO report)
[27] Ibid.
[28] Ibid.
[29] Obering interview.
[30] NIC report.
[31] UCS/MIT report, p. xxiv.

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