Volume 17, Issue 2
March 25, 2025
In his second week in office, President Trump signed an executive order on the creation of a new approach to U.S. homeland missile defense that breaks with longstanding U.S. missile defense policy. The plan, initially titled the “Iron Dome for America” but later rebranded by the Missile Defense Agency (MDA) as the “Golden Dome,” outlines a new policy that U.S. missile defenses should be designed to defend or deter “any foreign aerial attack on the Homeland” and “progressively defend against a countervalue attack by nuclear adversaries.” When plainly read, that includes nuclear-armed, strategic missiles from adversaries such as Russia and China.
This monumental ambition is a misguided and dangerous approach to securing the American homeland that will create enormous opportunity costs at a time of strained defense resources. The fundamental problem with any plan for a national missile defense system against strategic nuclear attack is that cost-exchange ratios favor the offense and U.S. adversaries can always choose to build up or diversify their strategic forces to overwhelm a potential shield. The fantasy of a missile shield runs against a core rule of strategic competition: the enemy always gets a vote.
In 1972, the United States and the Soviet Union acknowledged this reality when they agreed to limit their strategic missile defense systems through the Anti-Ballistic Missile (ABM) Treaty. The agreement sought to prevent open-ended competition to build more or new offensive weapons to overcome defenses that the other might deploy to try to stop incoming missiles in the event of a nuclear war. It helped pave the way for bilateral treaties limiting Soviet and U.S. strategic offensive forces in the 1970s and deep reductions in offensive nuclear forces beginning in the late-1980s.
The Golden Mirage
But in December 2001, U.S. President George W. Bush withdrew the United States from the ABM Treaty, arguing that Washington and Moscow no longer needed to base their relationship on their ability to destroy each other. Bush claimed, erroneously, that withdrawal was the only path toward permitting U.S. development of defenses against possible terrorist or “rogue-state” ballistic missile attacks.
After withdrawing from the ABM Treaty, the United States accelerated research and development and testing of missile defense systems, including on a limited defense against strategic ballistic missiles, to guard against potential threats from states such as North Korea. Since then, this limited approach has been continued by subsequent Democratic and Republican administrations.
The debate about the viability and advisability of missile defenses has, nevertheless, continued. Proponents have sought to expand funding for and the scope of U.S. theater and homeland missile defense systems, while skeptics have pointed out that many of these programs are cost-prohibitive, ineffective under real world conditions, or—in the case of systems with the capability to stop long-range (i.e. strategic) nuclear-armed missiles—destabilizing.
In contrast to the new executive order, the first Trump administration’s missile defense review, issued in 2019, sought to maintain the earlier U.S. missile defense doctrine while still pushing for research, development, and testing of ever more advanced and ambitious missile defense programs, stating that:
“While the United States relies on deterrence to protect against large and technically sophisticated Russian and Chinese intercontinental ballistic missile threats to the U.S. homeland, U.S. active missile defense can and must outpace existing and potential rogue state offensive missile capabilities. To do so, the United States will pursue advanced missile defense concepts and technologies for homeland defense.”
The earlier Trump missile defense approach generally tracked with the policy adopted after the United States withdrew from the ABM Treaty. That policy was designed to satisfy two goals: provide a limited defense against a simple North Korean nuclear-capable, ballistic missile threat while reassuring Russia and China that the United States was not seeking strategic defenses that would provide an impenetrable “shield” from behind which it could coerce other nuclear powers. Even a country with a medium-sized nuclear arsenal, such as China, might not be able to ensure the ability to retaliate against the United States if an effective strategic defense could “mop-up” the surviving nuclear warheads after a U.S. first strike.
The new executive order directs the Secretary of Defense to produce a “reference architecture, capabilities-based requirements, and an implementation plan” for the new Golden Dome program in 60 days. This rapid timeline is intended to ensure that the results can be included in the next presidential budget request, which is expected to arrive at Congress’ doorstep in May. The order itself provides hints at programs that are likely to be resurrected from the graveyard of ideas discarded by the MDA at the end of the last Trump administration.
Likely Missile Defense Program Additions and Challenges The Trump executive order names several missile defense programs that the Department of Defense must expand or initiate. Beyond these, there are also programmatic actions we can anticipate based on the MDA’s past budgetary requests and the current state of U.S. missile defense forces. Several of these programs are likely to face challenges – technical, financial, or operational. The executive order explicitly endorses two satellite programs, the Hypersonic and Ballistic Tracking Space Sensor (HBTSS) and the Proliferated Warfighter Space Architecture (PWSA). The HBTSS program was launched by MDA in 2018 to develop satellites capable of providing fire-control-quality missile tracking data for interceptors. As the name indicates, the program is designed to augment the U.S. military’s ability to defeat hypersonic threats. The first two HBTSS satellites were launched in February 2024, and more are planned for deployment in 2025. The PWSA is the Space Development Agency’s broader multi-purpose military space constellation program, which envisions hundreds of smaller sensing (“tracking”) and information relay (“transport”) satellites in low-earth orbit working to support the Department of Defense’s Joint All Domain Command and Control (JADC2) system. The executive order states that the PWSA should also deploy capabilities to perform the “custody” function – keeping track of enemy targets with enough precision for them to be destroyed by friendly forces. This function has historically been performed by the Air Force, the National Reconnaissance Office, or other agencies. The executive order also endorses the creation of an “underlayer and terminal-phase intercept capabilities.” The term “underlayer” denotes a supplemental missile defense system that can “underlay” a higher-level defense, such as the Ground-Based Midcourse Defense (GMD) system, providing additional interceptor shots at a target. In 2020, the MDA proposed allocating defense funds toward integrating the sea-based Aegis ballistic missile defense system and the land-based Terminal High-Altitude Area Defense (THAAD) system with GMD. Those proposals were trimmed by Congress in the fiscal 2021 and 2022 defense authorization bills, but may return this year. The MDA might also propose an increase in the number of U.S. Army THAAD units, land-based deployment of Aegis in the continental United States as recommended by the Atlantic Council report, or an increase in the production rate of interceptor missiles. The GMD program itself may also be expanded, although the number of GMD silos and sites was already increasing before the executive order. The Biden administration continued the first Trump administration’s plans for both a new GMD interceptor and for an increase in the number of silos in Alaska, some 20 of which have recently been completed. In the fiscal 2025 defense authorization act, Congress also tasked the MDA with establishing a third GMD site on the east coast of the United States by 2031, over the repeated objections of the Biden administration. These investments continue despite the lack of progress in overcoming an important challenge for midcourse intercept: distinguishing an incoming warhead from decoys—a task known as discrimination. According to Michael D. Griffin, a former undersecretary of defense for research and engineering in the first Trump administration, the United States is not “much better at that than we ever were.” On more uncertain ground is the executive order’s call for the development and deployment of space-based interceptors capable of boost-phase intercept of ballistic missiles. Historical plans for space-based interceptors have foundered on cost and practicality concerns. In 2004, a report sponsored by the American Physical Society estimated that the number of space-based interceptors needed to ensure intercept of just one rogue-state solid-fueled ballistic missile would be in the low thousands, with exact numbers varying with requirements and assumptions. While space-launch costs have significantly declined over the last decade, the cost of placing an interceptor constellation in space would still be high. The American Enterprise Institute’s Todd Harrison recently calculated that an interceptor constellation of 1,900 satellites would cost between $11 and $27 billion to develop, build, and launch. But Harrison warned that, “the cost of a space-based interceptor system scales linearly with the number of missiles it can intercept in a salvo.” An updated analysis released this year by the American Physical Society’s Panel on Public Affairs took into consideration the evolution of the North Korean intercontinental ballistic missile (ICBM) threat, and calculated that 16,000 space-based interceptors would be needed to defend against a ten-salvo launch of the Hwasong-18, a newer solid-fueled missile that is not even the most advanced ICBM North Korea is developing. Griffin, the former undersecretary of defense for research and engineering, emphasized at a March 19 webinar that, “it is not worth spending your money on a space interceptor constellation that is targeting the boost phase.” If the administration were to choose to demonstrate a bare-minimum technical capability to execute a space-based intercept of a simple missile threat in boost-phase, it would likely encourage U.S. rivals to plan for the worst while delivering little real added security to the nation. Finally, the executive order calls for the development and deployment of “non-kinetic” interceptor technologies, which can include directed-energy weapons such as lasers. The MDA hosts a Directed Energy Demonstrator Development technology maturation program that has received Congressional funding support above levels requested by the Biden administration. While this program and other laser research efforts within the department may be expanded under the second Trump administration, laser technology for strategic missile defense remains far from deployment. The American Physical Society’s 2024 report concluded, after surveying current research efforts, that lasers capable of intercepting ICBMs would not likely be feasible before 2035. A recent Atlantic Council report, largely favorable to investments in laser technology, describes them as a “long term” prospect. |
Accelerating the Arms Race
But beyond specific programs, the new executive order also heralds a stark shift in the underlying U.S. approach to missile defense, legitimizing an ambitious new vision of America’s strategic posture that has not gone unnoticed in Moscow and Beijing. While proponents of missile defense argue that costs and technologies are both trending in favor of the development and deployment of defense systems once thought fanciful by technical experts, the strategic challenges associated with missile defense have not gone away.
Proponents of a more ambitious missile defense effort do not have easy answers to the question of how strategic stability will be managed if the United States actually pursues the missile defense plan ordered by Trump’s Golden Dome executive order. For example, a recent op-ed by two supporters of a space-based approach to missile defense notes traditional concerns about “destabilizing and undermin[ing] nuclear deterrence,” but provides no discussion of the problem.
There are already signs that the first Trump administration’s incremental missile defense investments, such as ordering a 2020 flight test of the Aegis sea-based missile defense system against an ICBM-range target, have affected other nations’ thinking on the stability of the nuclear order. According to one analysis, Chinese experts’ “long-standing concerns about [missile defense] systems intensified in the years before Beijing began building the new silo fields.” While the ongoing Chinese nuclear build-up is probably also influenced by broader political considerations, it is evident that the small size of the arsenal posed survivability concerns.
The development by both Russia and China of hypersonic glide vehicles for potential delivery of nuclear warheads, as well as Russia’s exotic strategic weapons concepts, are likely also attempts to hedge against unforeseen breakthroughs in U.S. ballistic missile defense capabilities.
The Red Herring of a Homeland Cruise Missile Threat
A particularly unfortunate aspect of the missile defense discourse in recent years has been the bundling of cruise, ballistic, and hypersonic missile threats into calls for comprehensive homeland defense. Creeping improvements to U.S. ballistic missile defenses pose the greatest threat to strategic stability and present the greatest costs and technological challenges. In contrast, there is a debatable case for homeland cruise and hypersonic missile defense, which is technologically feasible, potentially still quite costly, but also less likely to pose risks to strategic stability.
An example of this unfortunate tendency to conflate ballistic and cruise missile threats is presented not only in the “Golden Dome” executive order, but also in the aforementioned Atlantic Council report, which argues for an expanded and layered homeland missile defense system to protect civilian and military targets from limited long-range strikes by Russia or China. These adversaries might, in the case of an all-out war with the United States, seek either to use long-range strikes to send coercive signals as part of a graduated escalation strategy, or conduct a broader campaign of strikes to disrupt the United States’ ability to wage war effectively.
There are several problems with the report’s arguments.
First, there is no particularly new or urgent threat posed by limited use of nuclear weapons against the homeland. For either country to launch a limited nuclear strike against the United States would be extremely risky and relatively high on the escalation ladder. The United States has proportionate responses to such an attack in part because it has had to think about this particular rung of the ladder for decades.
The strategic logic behind such a strike would also be faulty. A limited use of nuclear weapons to shock and fracture the NATO alliance would not be helpful to Russia if targeted at U.S. home-soil. The horror would likely commit the United States irrevocably to the conflict, rather than split it from its allies, binding them tighter in shared suffering and determination. Instead, the more important concern is a Russian limited strike against a NATO ally that would aim to heighten the fear of potential costs in the United States.
With regard to China, both the Department of Defense, in its annual reports on China’s military power, and the Strategic Posture Commission speculate that the country is most likely to violate its own no-first-use doctrine to prevent conventional defeat during an attempted invasion of Taiwan. A limited nuclear strike against the U.S. homeland would expand the conflict while inviting proportionate retaliation that would make a Chinese conventional victory even less likely.
Second, when it comes to conventional attacks on U.S. homeland targets, the vast majority of both potential adversary arsenals is composed of cruise missiles, not ballistic missiles. Land-attack cruise missiles comprise the “backbone” of Russia’s conventional long-range strike capabilities. The only potentially relevant exceptions include the Kh-47M2 Kinzhal air-launched ballistic missiles, with a reported range of up to 2,000 kilometers after launch from a bomber or fighter-jet, and the newly unveiled Oreshnik intermediate-range ballistic missile. U.S. officials have confirmed that Ukraine has shot down at least one Kinzhal using the Patriot air defense system. Similarly, the few Chinese missiles that could hypothetically target the U.S. homeland would be ship-launched land-attack cruise missiles, brought toward the U.S. coast by surface vessels or submarines. Thus, any argument making an urgent case for homeland missile defense is strongest when it addresses the cruise missile threat and weakest when it is used to justify ballistic missile defense.
Third, the focus on a new cruise missile threat makes questionable sense given potential enemy capabilities and strategic logic. Both Russia and China would find themselves with many closer-range targets for their considerable long-range strike capabilities in the territories of U.S. allies.
While Russian doctrine does outline a role for the use of conventional long-range strike to destroy critical assets in enemy rear areas, the specific threat to the United States—as opposed to NATO targets in Europe—is unclear. A 2023 assessment by RAND estimated that acquiring a stockpile of conventional long-range missiles that could satisfactorily ensure the destruction of NATO air fields in Europe alone would take Russian industry a decade of production, assuming both increased financing and improved industrial performance.
The authors of the Atlantic Council report note statements by the head of U.S. Northern Command that China seeks to “disrupt, delay, and degrade force flow” as well as “erode support for a conflict.” Nonetheless, they concede that “absent from [the Chinese literature’s] discussion of precision strikes is the explicit reference to targets in the opponent’s homeland or rear area” and that there is “some danger in overinterpreting the intent of China’s leadership from [People's Liberation Army] military capabilities.”
More fundamentally, it is not in the interests of either China or Russia to launch kinetic strikes to damage the U.S. homeland early in a crisis as this would likely draw the United States deeper into a conflict. The theory of a potential coercive strike that deters the United States from involvement seems constructed on a highly speculative model of the psychology of U.S. decision-makers.
Fourth, homeland cruise missile defense would still be costly. Estimates differ depending on which targets are to be defended, the types of sensors integrated into the system, and the choice of interceptors. A Congressional Budget Office report from 2021 presented four options ranging in price from $77 billion to $179 billion over a 20-year period. A 2022 system proposed by the Center for Strategic and International Studies came to a lower cost figure—only $32 billion over 20 years—by designating fewer targets for defense, relying on the integration of existing sensors, and preferring surface-to-air missiles for interception over fighter jets.
Given the executive order’s emphasis on protecting the entirety of the United States, and particularly its focus on defeating a “countervalue” attack, costs for a cruise missile defense system that corresponds with the president’s goals would likely be on the higher side of estimates.
Arguments for homeland cruise missile defense neglect other possible options for managing the purported threat. These might include hardening of vulnerable military bases, redundancy of key military infrastructure, deceptive practices to prevent effective strikes, and investment in rapid reconstitution of critical capabilities. Given the expense of homeland missile defense, the taxpayer deserves persuasive cost-benefit analyses and discussion of these—and other—options.
Conclusion
Over the past decades, the roughly $250 billion spent on the MDA and its predecessor organizations have bought a U.S. missile defense capability still too fragile to provide confidence in Washington, but threatening enough to drive worst-case thinking in Beijing and Moscow.
The latest edition of the annual report of the Department of Defense’s Director, Operational Test and Evaluation, concludes that the GMD system is capable only of defending the homeland from a small number of ballistic missiles with a range over 3,000 kilometers, and only when those missiles employ simple countermeasures alone. Likewise, the theater missile defense systems, represented by Aegis, THAAD, and Patriot, can defend against only a small number of medium- and intermediate-range missiles at a time.
Despite the incremental improvements in U.S. missile defense technology, the basic value proposition of these capabilities has remained the same. Investments in ambitious strategic homeland missile defense have failed to deliver, while the rhetoric backing these investments has accelerated and inflamed the nuclear arms race.
In contrast, theater missile defense has fared comparatively better, delivering notable successes such as the recent shoot-down by Aegis-equipped ships of Iranian missiles targeting Israel. But the relative success of theater missile defense is due in large part to the lower bar of the technical challenge: shorter-range missiles are typically slower and easier to intercept.
If the second Trump administration wants to pursue a maximalist vision of a “Golden Dome” to offer a mirage of strategic defense for the homeland, the president’s stated goal of engaging Russia and China in talks on “denuclearization” will become significantly more difficult to achieve. Russia has made clear in previous rounds of nuclear arms control talks that it considers strategic missile defense to be highly destabilizing to the U.S.-Russian nuclear balance of terror.
Instead of a maximalist approach that deceives America into a false sense of invincibility, the United States should adopt a “talk small, invest smart” approach to missile defense. That would mean assessing not only the technical feasibility and simple costs and benefits of missile defense proposals, but also the long-term opportunity costs and the appropriateness of alternatives such as negotiated reductions in strategic arsenals. —XIAODON LIANG, senior policy analyst