National missile defense is not a new idea, but in a world of expanding threats and technological advances, many argue it’s one whose time has come. There’s a case to be made that the Cold War deterrence paradigm of mutually assured destruction (MAD) is no longer valid in the face of rogue-state nuclear proliferation, and that Israel’s Iron Dome and related systems demonstrate the potential for such defenses at achievable costs.
President Donald Trump can be counted among those making that case. He signed an executive order in January directing the secretary of defense to submit a plan outlining architecture, requirements, and an implementation plan for a next-generation missile defense shield. This “Iron Dome” for America should defend the United States from “ballistic, hypersonic, advanced cruise missiles, and other next-generation aerial attacks,” according to the White House, which called such attacks “the most catastrophic threat facing the United States.”
Detractors argue that a comprehensive defense is not technically feasible without exorbitant cost, and that even if it were feasible, it would result only in creating strategic instability, potentially engendering a new arms race while providing only fleeting advantages. Weighing arguments on both sides of the debate requires a basic understanding of the technologies and theories involved.
Missile defense 101.
Missile defense systems are designed to locate, track, and destroy incoming missiles by intercepting them before they reach their targets. To destroy a ballistic or hypersonic missile, the missile must be defeated in its boost, mid-course, or terminal phase. It’s most vulnerable in the boost phase, when its path is relatively slow and predictable. A missile in mid-course transits through space, which presents targeting challenges. And a missile in its terminal phase travels at high speeds and steep trajectories leaving very little time in which to intercept it. The U.S. has deployed interceptor missiles, consisting of a booster rocket and a “kill vehicle” that either collides with or detonates near an incoming missile, both overseas and in the homeland. Kill mechanisms, the means of destroying missiles, can be kinetic, e.g. using missiles or other projectiles, or non-kinetic, using cyber technology or directed energy such as lasers. The executive order also directs the Department of Defense to explore options for destroying missiles before they even launch, methods that would presumably include cyber and sabotage.
In addition to kill mechanisms, countering objects crossing continental ranges at high speeds and/or low altitudes requires complex detection, tracking, and command-and-control systems spanning the globe to enable continuous tracking and instantaneous coordination between multiple theaters and layers of command.
Defenses must also address two distinctly different types of missile threats. Ballistic missiles, on the one hand, follow a computable trajectory. Defending them requires putting sensors and interceptors between the launcher and the target and then shooting at the missiles along their flight path.
Hypersonic and cruise missiles, however, (including uncrewed aerial systems and, loosely, stealth aircraft) can maneuver and approach a target from any direction and altitude. Stopping these missiles requires defensive systems capable of sensing and firing in any direction or at very long ranges. The impracticality of protecting an entire continent from threats approaching from any direction and altitude has led to an emphasis on “terminal” defenses capable of defending specific areas, such as densely populated cities.
Responses to increasing missile threats.
The list of unfriendly countries that can threaten the United States with missiles or bombers is short but significant. Russia has about 540 strategic delivery systems, and China around 300. North Korean missile numbers are harder to come by, but probably track closely with their 50 or so nuclear warheads. Iran’s missile arsenal can threaten Europe but, so far, not the U.S.
Effective missile defense is a relatively new phenomenon, even if the idea of limiting attacks is not. The United States and the Soviet Union signed the Anti-Ballistic Missile Treaty in 1972, under which each side was allowed one missile defense site. President George W. Bush withdrew from the treaty in 2002 in the face of increasing worldwide missile threats and the futility of differentiating between increasingly sophisticated anti-aircraft technology and anti-missile systems.
Current U.S. missile defense efforts are overseen by the Pentagon’s Missile Defense Agency, which traces its roots to President Ronald Reagan’s Strategic Defense Initiative (SDI). It is tasked with overseeing all missile defense development efforts, and coordinating with allies and partners for national defenses as well as defenses in specific theaters of operations.
Coordination with global allies is useful not just to fulfill treaty commitments, but also because they can provide prime locations for key missile defense components. Pituffik Space Base in Greenland, for example, is situated to provide early warning in the event that Russia launches a missile toward the U.S. over the North Pole.
What are the current capabilities?
As of today, nine nations have credible anti-missile systems either deployed or in advanced stages of development. None of these could be called truly national defense systems, with the possible exception of Israel’s simply because, with a land mass about the size of Maryland, it’s small enough to fit under the umbrella of both tactical and theater interceptors. The U.S. Ground Based Midcourse Defense provides limited homeland defense with fewer than 50 interceptors in Alaska and California. The system uses ground-based interceptors carrying exoatmospheric hit-to-kill vehicles that are directed to incoming missiles using ground radar and onboard sensors. The system, which has cost about $63 billion to develop and deploy, has had 12 successful tests out of 22 attempts, and is presented as an effective defense against a limited strike. The Pentagon’s 2024 budget request for missile defense was $10.9 billion, about 80 percent of which was earmarked for research and development.
Most nations’ systems are land-based, but there are some sea- and even air-launched capabilities. Many are designed as both anti-missile and anti-aircraft systems, and almost all use kinetic kill mechanisms. Directed energy systems are in development with a few limited deployments, but still considered a nascent capability. That’s because such systems require enormous amounts of energy to function and are susceptible to environmental factors like clouds, because the target needs to be within line of sight. On the plus side, since the “projectile” is merely a beam of highly concentrated energy, magazines are virtually unlimited and the cost per firing is minuscule compared to the missiles being intercepted.
National missile defense today would either take orders of magnitude more gear than we have now, or an acknowledgement that “national” really means defending a limited set of targets. Trump’s executive order tacitly admits this fact by placing the initial focus on defending civilians and infrastructure rather than military targets.
Missile defense theory v. practice.
While it’s not surprising to hear defense companies and politicians with facilities in their districts advocate for national missile defense, serious strategic thinkers and organizations also present credible arguments in its favor. The primary argument for national missile defense is that the government’s first and foremost duty is to protect the homeland and its citizens. Although mutually assured destruction may be an outmoded idea, a credible missile defense can also have a deterrent effect on an adversary’s strategic calculus by decreasing its odds of success and increasing the odds of a retaliatory response. And as with the space program, advanced missile defense would likely result in spinoff technologies with immense potential for military and commercial applications.
Thoughtful arguments against missile defense largely come from organizations that trace their lineage to Cold War arms control advocacy, based largely on cost and technology. Undoubtedly, it will be expensive. Costs are impossible to estimate without knowing what recommendations the Pentagon will make, but will almost certainly range into the hundreds of billions of dollars. Even if a national umbrella is possible—a point detractors are unlikely to concede—and no matter how many of an adversary’s missiles can be stopped, an enemy may be able to produce more missiles to overwhelm the system at less cost than creating a system to defend against them.
The way forward.
As Trump’s executive order seems to acknowledge, missile defense systems cannot credibly defend the entire United States now or even in the near- to mid-term. Several challenges must be overcome for missile defense to become “national.”
First, for missile defense to become affordable the cost per intercept must radically decrease to far less than the cost of an incoming missile. Directed-energy weapons present opportunities here and are advancing, albeit with significant technical and operational challenges. Next, while we can currently detect and track intercontinental or theater ballistic missile launches, maneuverable hypersonics and uncrewed systems require radically enhanced surveillance capabilities, to include high- and low-altitude detection along the entire U.S. border at a minimum. Finally, terminal defense cannot be the primary focus. There are simply too many points on a continent (plus Alaska, Hawaii, and Guam) to defend. Anti-launch, boost, and mid-course options are required. These may include forward deployed systems, space-based systems, and cyber operations, among other options.
The late Israeli leader Shimon Peres said, “If a problem has no solution, it may not be a problem, but a fact—not to be solved, but to be coped with over time.” The problem of how to defend America from missiles may not present a ready solution, at least in the near term. But there are ways to strengthen existing defense systems and essentially create new facts. The question will be where the incremental benefits are justified by the incremental costs.
