Last week, U.S. President Donald Trump signed an executive order directing the Defense Department to build an “Iron Dome” missile defense shield over the United States. Almost immediately, some experts expressed skepticism, comparing it to former President Ronald Reagan’s unrealized “Star Wars” plans in the 1980s and questioning whether it would be possible to design a perfect missile shield over such a large country.
But Trump is right. A U.S. homeland missile defense system is both technically possible and necessary to defend the country from 21st-century threats.
The bipartisan consensus on U.S. homeland missile defense policy for the past several decades has been focused on a system that can defend against limited threats from North Korea and, in the future as the ranges of its missiles increase, possibly Iran. As such, the United States has deployed 44 ground-based interceptors (GBIs) in California and Alaska. The interceptors are designed to crash directly into enemy offensive missiles in a technological feat that has been likened to hitting a bullet with a bullet.
Forty-four interceptors may be sufficient for dealing with small salvos from rogue states, but they would be easily overwhelmed by a larger attack. Moreover, the current system is designed for ballistic missiles and not a wider range of 21st-century threats, which now includes conventional and nuclear-armed cruise and hypersonic missiles.
Washington has long ruled out missile defenses against great powers like China and Russia, arguing that it should instead rely only on nuclear deterrence to prevent attacks from these peer adversaries. Proponents of this view argue that accepting mutual vulnerability creates “strategic stability” as both sides understand they have too much to lose from a major war. They contend that deploying strategic missile defenses could be “destabilizing.”
Adversaries fearing that U.S. missile defenses could stop their nuclear deterrent might race to build enough missiles to overwhelm U.S. defenses. Worse, they might fear that a strong defense gives America a first-strike option, tempting adversaries to actually launch a preemptive attack first in a crisis or war before their missiles are wiped out.
Unfortunately, this approach of simply leaving the U.S. homeland vulnerable to adversary strategic attack has not led to stability. On the contrary, backed by nuclear coercion, Russia has launched the biggest land war in Europe since World War II. Meanwhile, China has embarked on the biggest nuclear arms buildup since the height of the Cold War, harasses U.S. allies and partners in the Indo-Pacific daily, and continues to threaten military force to take over Taiwan.
In addition, Moscow and Beijing apparently did not get the memo that building missile defense systems is destabilizing; they have both built and are now modernizing air and missile defense systems to protect their homelands from attack, including from the United States.
At the same time, both powers are building a range of advanced offensive missiles that pose a vital threat to the United States. In sum, the current approach is not working, and Washington needs to take action to protect itself and to restore strategic deterrence globally.
The need for missile defense becomes clearer if one imagines a great-power war over Taiwan. Take this scenario: China invades Taiwan and the United States mobilizes forces to come to the defense of the island. China then launches two dozen conventional hypersonic and cruise missiles at U.S. bases and cities in Guam, Hawaii, California, and Texas.
Given that the current U.S. system was designed for limited ballistic missile threats, most, if not all, of these missiles would get through and hit their intended target. Washington’s ability to project power forward in the defense of its allies would be degraded, and a U.S. president might decide to simply back down rather than risk any further loss of American life.
But it does not make sense to leave the homeland vulnerable to this kind of attack as a matter of policy. After all, the first and most important vital interest of any U.S. president is to defend the homeland.
Developing an Iron Dome for the United States could defeat this kind of attack.
Building a perfect system that could stop a large-scale attack with hundreds or thousands of Russian or Chinese nuclear-armed missiles may be impossible—for now—but Washington should still design a more limited system to protect key sites, such as military bases, critical infrastructure, and the national capital region. Such a system would take America’s juiciest targets off the table for an enemy attack.
Such a defense would also help deter an enemy attack in the first place. If China and Russia know that a limited attack would likely be shot down, then they would face a choice between going big or going home. Going big, by launching a massive attack on the United States, could escalate into a major nuclear war—one that would threaten their leaders, nuclear forces, militaries, and war-supporting industries, giving U.S. adversaries good reason not to attack at all.
In addition to defense and deterrence, an Iron Dome for the United States would contribute to the assurance of allies. South Korean officials and experts, for example, have asked me whether the United States—as it becomes more vulnerable to missile threats—may be less willing to defend Seoul in a crisis.
Lacking assurance from the United States, South Korean leaders could choose to take matters into their own hands, including doing things that would be contrary to U.S. interests, such as building their own nuclear weapons and sparking a nuclear arms race in Asia. A U.S. Iron Dome system, on the other hand, would assure allies that Washington can help in their defense and protect its homeland at the same time.
The logic for a U.S. Iron Dome is so strong, it is becoming the new bipartisan consensus. The 2023 final report of the 12-person, bipartisan Congressional Commission on the Strategic Posture of the United States (a commission on which I served) unanimously recommended that “[t]he United States should develop and field homeland IAMD [integrated air and missile defense] capabilities that can deter and defeat coercive attacks by Russia and China.”
For decades, critics have argued that missile defenses do not work, but the facts have changed. Missile defense technology has greatly improved in recent years. The world has witnessed the remarkable success of Israel’s Iron Dome system, which successfully defended Israel against massive Iranian salvos of missiles and drones in two attacks in April and October of last year.
In tests, the United States’ current GBIs have a roughly 50 percent success rate. Moreover, it is possible to shoot multiple interceptors at each incoming missile, bringing the chance of a successful interception closer to 100 percent.
A homeland missile defense system does not need to be perfect to be effective. If there were a missile headed for my house, I would take a 50 percent chance of a successful defense over the 0 percent chance without a missile shield. And again, even an uncertain chance of success would contribute to the deterrence of adversaries and the assurance of allies.
Designers of the new U.S. Iron Dome architecture should pursue a layered defense to maximize its effectiveness. As my colleague Rob Soofer writes in a new Atlantic Council report, this should include an expanded set of interceptors, perhaps to 100 or so. They can be reinforced by an underlayer of SM-3s (a missile currently used in U.S. Aegis theater missile defenses), Terminal High-Altitude Area Defense missiles, and cruise missile defenses.
Finally, U.S. missile defenses should move to space. Trump’s new order directs the Pentagon to develop and deploy “proliferated space-based interceptors.” The laws of geometry and physics mean that it is easier to intercept an incoming missile from space than from the ground.
A ground-based interceptor must attempt to hit an incoming missile in its midcourse or descent phase, when the missile is moving fastest and where it can potentially maneuver and release decoys to confuse the defender. A space-based interceptor, on the other hand, can target a missile in its most vulnerable boost phase as it struggles slowly upward on a predictable trajectory to escape Earth’s gravitational pull.
Reagan and his advisors understood this in the 1980s, prompting them to envision the original Star Wars system. They were ahead of their time, but technology has caught up. Elon Musk’s SpaceX has drastically slashed the cost of space launch, rendering a proliferated system of space-based sensors and interceptors feasible and affordable. You cannot hit what you cannot see, and a space-based sensor layer, along with ground-, sea-, and air-based radars, would provide the best chance to detect incoming enemy missiles.
It was Soviet fears that Moscow could not keep pace with Washington’s planned Star Wars system that helped lead to the peaceful conclusion of the first Cold War, and the United States is positioned to outmatch China or Russia in a missile defense competition in the second Cold War.
Critics will argue that an Iron Dome for the United States will risk kicking off a new destabilizing arms race with China and Russia. The truth is China and Russia are already racing—producing new offensive and defensive missiles—as Washington sits on the sidelines.
Yes, building an American Iron Dome will be costly, but it will be less expensive than a future Chinese or Russian strategic attack on the U.S. homeland.