In his recent address to a joint session of Congress, President Donald Trump reiterated his desire to build an air and missile defense system for the entire United States. Invoking Ronald Reagan’s Strategic Defense Initiative or “Star Wars” vision of 1983, Trump said that we now have the technology to do what Reagan intended but was unable to achieve. There is at least partial evidence to support Trump’s goal: Ukraine has intercepted large fractions of the cruise missiles, ballistic missiles, and drones that Russia has unrelentingly bombarded its cities with since 2022, and Israel’s Iron Dome aided by American defense systems largely neutralized huge Iranian attacks against Israel in both April and October of 2024. Remarkably, even though some 500 objects of various types were shot at Israel, and the attacks were generally expected (allowing greater vigilance by defenses), casualties and damage were minimal.
Inspired by these successes, the Trump administration issued an executive order on the subject within a week of its inauguration, on January 27, and asked the Department of Defense to come up with a detailed architecture within 60 days to kickstart the budgetary process. The order directed that the defense system should include improved space-based sensors as well as defensive weapons in space and on Earth, here in the United States but also near possible adversarial launch sites for “boost-phase” defense—and with an eye toward defeating threats not just from small extremist states like North Korea but also peer and near-peer competitors (read: China and Russia).
Trump is right that the technology for missile defense today is much better than before, but his ambitions will need readjustment. An advanced country like China or Russia could deploy countermeasures to fool many types of possible defenses or simply build more offensive nuclear weapons to overwhelm them. Quite apart from the possibility that a huge missile defense deployment could kindle an arms race (recall that Russia used to have five times as many nuclear weapons as the nearly 6,000 it possesses today, and it could build more again), the size and scale of the defense architecture being proposed is daunting.
An American Iron Dome isn’t the answer
Yes, Israel has an Iron Dome. More specifically, it has three main layers of defense throughout its territory, especially in the populated coastal, central, and northern regions. But its land area is only a bit more than 8,000 square miles; that of the United States is almost 4 million square miles, or more than 450 times greater. Indeed, the Iron Dome typically only shoots at incoming weapons around 10 miles away; tens of thousands of defensive batteries would be required to defend the whole United States with similar coverage. Moreover, at present, Israel has no nuclear-armed adversaries, whereas the United States does. Our Iron Dome—or the “Golden Dome,” as Trump calls it—would therefore need to have even higher confidence levels of a successful missile intercept.
Luckily, we don’t need to worry too much about short-range rockets being fired at our cities from nearby locations or American soil itself. The current American national missile defense system, more of an “iron mesh” than an iron dome, includes 44 long-range interceptors based in California and Alaska—positioned there for maximum effectiveness against nuclear-armed North Korea, which has tested several long-range intercontinental ballistic missiles (ICBMs) over the past decade and could perhaps field a few dozen. We do not really know if North Korea could deliver a nuclear warhead that would survive atmospheric reentry and detonate on American territory; based on what is publicly known about Pyongyang’s testing history to date, the odds are modest at best. (The existing West Coast defense system is not optimally positioned to address a possible Iranian threat to the United States—but at present, there is no such long-range missile threat from Iran, nor an Iranian nuclear weapon to place atop any such missile.)
Yet Russia has more than 1,000 long-range warheads on its missiles, and soon China will, too. Even though no country has actually tested a real nuclear warhead at the end of a long-range missile flight, countries with the science and technology capacities of Russia and China have ways to simulate the effects of launch and atmospheric reentry. Therefore, for decades, we have wisely assumed that either of those countries could indeed strike American territory—and in the case of Russia, could either saturate any defenses we deployed or use decoys to foil them. Both sides might well overrate the possible effectiveness of enemy defenses while underrating their own, providing grist for an offense-defense arms race. That was the logic that led to the Anti-Ballistic Missile Treaty of 1972, which sharply curtailed allowable defenses. The United States withdrew from the treaty in 2002 but interestingly never deployed a defense system that would have violated the treaty’s numerical limits on interceptors.
One more key piece of the puzzle: we have hundreds of interceptor missiles deployed on ships or on mobile land-based batteries that were originally designed to handle short-to-medium range air and missile threats but may now be capable of helping defend the country against long-range ICBMs or submarine-launched ballistic missiles (SLBMs), if properly positioned. So, if Trump wished, he could fairly quickly construct an improvised missile defense system that would complement and deepen the capability provided by the dedicated system in California and Alaska. (Indeed, the first Bush administration had a similar concept in mind with its Global Protection Against Limited Strikes system that, back in the 1990s, would have placed radars and interceptors at half a dozen inland sites in the United States—though it was eventually deemed not quite worth the estimated $100 billion price tag.) But Trump is thinking much bigger than that, as noted, and most strikingly, he wants to put weapons in space.
Weapons in space?
Here’s the problem with that idea: weapons based in low-Earth orbit (within a few thousand kilometers of Earth’s surface), as they must be to have adequate range and power to reach ICBMs or SLBMs in flight, move around constantly. That means you need up to several dozen at various places around the Earth to be sure that one will be in the right place when the time comes. This “absentee ratio” problem makes costs exorbitant if the system is designed to counter a large-scale synchronized attack.
Futurists, however, find perennial appeal in a system of orbiting space-based lasers. So, imagine a space-based laser that can fire 20 shots with its fuel supply (quickly pivoting from shot to shot and homing in on its prey with uncanny pointing accuracy). And assume that the absentee ratio is 20-to-1 (that’s pretty good, actually; absentee ratios can be even higher). In that case, a country would need 20 satellites in space to be assured of having one within lethal range of nuclear-tipped enemy missiles at the right moment—and thus of being able to fire 20 good shots at threatening objects. If the enemy can shoot hundreds of threatening objects at you—let’s say 500—that means you would need 500 space-based lasers (of which about 25, each with the capacity to shoot down 20 threatening objects, could be expected to be in the correct position to defend). With each one effectively the equivalent of at least a Hubble Telescope in technology and cost, given that it needs a huge mirror to focus and direct the beam (in addition to the laser itself, and its fuel supply), we are looking at perhaps a $500 billion price tag for a comprehensive space-based missile defense. Secretary of Defense Pete Hegseth hopes to free up $50 billion a year in the defense budget for new purposes; even if he is able to find such savings and devote them all to such a missile defense system, it would take a decade just to build the space-based part alone.
Alternatives to consider
Star warriors need not despair: there are many more modest and worthwhile ideas to consider, generally not involving weapons in space. Rob Soofer and his team at the Atlantic Council propose a system that would provide limited defense for key military sites and some cities, deepening the protection that the current California-Alaska system can provide today. Such a system couldn’t handle a massive Russian or Chinese strike but could protect against accidental, unauthorized, or “rogue state” launches or limited strikes intended to coerce the United States into some kind of capitulation without provoking an all-out nuclear response. It would also run less risk of provoking an all-out arms race, given its limited capabilities. And in a world of proliferating drones, launched from a nearby country, ship, or even American soil, it may make sense to think about modest-scale defenses not only against ballistic or cruise missiles but short-range smaller airborne threats as well.
Moreover, with Russia and China increasingly in strategic cahoots and China building up its nuclear arsenal, the United States and its allies will need to think about an appropriate response. Some will advocate a big offensive nuclear weapons buildup. It may be a better investment, however, to think about a limited national missile defense.
So, as long as Trump doesn’t take his Iron Dome vision too literally, he may just spark a useful debate about future American territorial defense in the modern age.