Trump’s missile shield pledge amid rising global threats

Just before Donald Trump became the Republican nominee, the party outlined its foreign-policy objectives: “Prevent world war three, restore peace in Europe and the Middle East, and build a great Iron Dome missile-defence shield over our entire country”. The latter has become a central promise of Trump’s campaign. In his acceptance speech, he vowed that an American missile shield would ensure “no enemy can strike our homeland”, adding it would be “built entirely in the USA”.

In today’s era of wars, weapons proliferation, and nuclear threats, missile defence is more relevant than ever since Ronald Reagan’s 1980s space-based systems. It’s not just MAGA supporters who are keen; Ursula von der Leyen, president of the European Commission, recently pledged support for “a European Air Shield”.

Conflicts in Ukraine and the Middle East have tested new projectiles—from small drones to long-range hypersonic missiles—and the technologies designed to counter them. As this article was published, Israel, with its allies, was prepared to counter another large-scale aerial attack by Iran, following its April launch of 300 projectiles at Israel. On August 10th and 11th, Russia struck Ukraine again using North Korean missiles and Iranian-designed drones.

Trump vows in his next term to “build a great Iron Dome defense shield” even though it would be completely useless because the US isn’t threatened by short-range rockets pic.twitter.com/y8m8IOTLw9

— Aaron Rupar (@atrupar) July 28, 2024

Missile defences have been tested and performed well, encouraging those who wish to develop more ambitious shields. However, missiles are evolving, becoming more manoeuvrable and harder to track. China is expanding its missile arsenal, and proliferation is putting advanced weapons in the hands of non-state actors like Houthi rebels in Yemen. This necessitates a new generation of sensors and interceptors, with a substantial price tag.

Air and missile defence involves interlocking systems. Sensors, typically radars, detect targets like drones and missiles. Computers process the data to determine their paths. This information is passed to guns or interceptor missiles, usually on the ground or sometimes on planes, which then attempt to neutralise the threat by colliding with it or exploding near it.

Each component has a specific role. Anti-drone guns cannot take down ballistic missiles; interceptors designed for nuclear-armed intercontinental-range ballistic missiles (ICBMs) in space cannot handle small drones. Therefore, defences are layered to address threats of different ranges, speeds, and trajectories.

The concept of an Iron Dome over America is impractical. The Israeli system intercepts small, short-range rockets fired by militants in Gaza and Lebanon, which are irrelevant to America (“unless Wisconsin plans on rocketing Chicago,” notes Jeffrey Lewis, an expert). America employs point defences at key areas. One such system has protected Washington, DC, for almost 20 years, intercepting planes and cruise missiles from a range of about 40km.

Trump likely refers to the more ambitious task of detecting and intercepting nuclear-armed ICBMs aimed at America. This is challenging. The missile is vulnerable during its slow “boost” phase after take-off, but this requires a quick response on enemy territory. It’s easier to hit during the “midcourse” phase, but by then it has cooled down while hurtling through space without boosters, making it hard to track with infrared sensors. Intercepting the warhead on its final approach is difficult due to its speed of about 7km per second.

Counter-ICBM defence has been controversial. After George W. Bush withdrew from the US-Soviet Anti-Ballistic Missile (ABM) Treaty of 1972, America spent over $67bn on the ground-based midcourse defence (GMD) system, which relies on 64 interceptor missiles in Alaska and California, guided by large radars on land, at sea, on destroyers, a repurposed oil platform, and sensors in space. This system is meant to protect against countries with small nuclear arsenals, primarily North Korea, which tested a missile capable of reaching major American cities in 2017. Critics argue the system is flawed—nine out of 21 intercept tests since 1999 have failed—and that it has spurred an arms race with Russia and China, who claim it undermines their deterrents and incentivises them to develop more and different missiles to bypass it.

Advocates respond that the four most recent GMD tests, the last in December, succeeded. Some want to expand it further. Bob Peters of the Heritage Foundation, a pro-Trump think-tank, suggests that Russia or China might launch a dozen or so “low-yield” nuclear weapons against US military targets, assuming America would hesitate to retaliate massively for fear of further strikes against its cities. Peters believes America should build defences capable of intercepting “upwards of 100 inbound threats”, forcing adversaries to launch many more missiles to succeed—a risky strategy. This idea horrifies most arms-control advocates. Only America has the resources to consider such a shield seriously. Most missile defence focuses on more modest, largely non-nuclear threats: conventional missiles fired over hundreds of kilometres, rather than nuclear ones fired across oceans.

Recent wars provide encouraging evidence. Last year, Israel conducted the first-ever interceptions of Iranian ballistic missiles, fired from Yemen, using its Arrow 2 and 3 systems, which handle long-range threats. The latter achieved the first wartime interception in space. On April 13th, Israel, America, and other allies shot down 99% of the 550-plus projectiles fired by Iran and Hizbullah in one night, the largest missile barrage in history, according to Israel’s armed forces.

Ukraine’s record is more inconsistent. Between May and October 2023, Ukraine intercepted 73% of Russian missiles, according to the Wall Street Journal. Over the next six months, this dropped to 46%. However, Ukraine claims that American-made Patriot batteries have intercepted 40% of Russia’s advanced air-launched Kinzhal missiles, which, if true, is impressive. Countries often exaggerate their defence success. However, Patriot and similar European systems have undeniably prevented heavy casualties and significant damage. In Israel, “thousands of lives have been saved,” estimates Moshe Patel of Israel’s Missile Defence Organisation.

The defenders’ task is becoming tougher. Precision guidance is now ubiquitous. Scuds fired by Iran and Iraq in the 1980s, or by Iraq against Israel in the 1990s, were inaccurate terror weapons, only good for hitting cities. Today, Iran and its militia allies fire weapons with pinpoint accuracy. More projectiles must be intercepted now than a decade ago, as more would hit their targets otherwise, risking quicker exhaustion of interceptor batteries.

Missile trajectories are also changing. Previously, missiles fell into two categories: cruise missiles, which are manoeuvrable, fly close to the ground, making them harder to track but slower; and ballistic missiles, which follow predictable parabolic trajectories, making them easier to spot early. The complication is the emergence of weapons blurring these categories, designed to confound American defences.

Some new weapons are fast, low, and erratic: aeroballistic missiles like the Kinzhal and North Korea’s KN-24 spend more time within the atmosphere after re-entry and can manoeuvre during flight. Hypersonic glide vehicles (HGVs) like China’s DF-ZF are launched on rockets but then glide through the atmosphere like cruise missiles. Small suicide drones challenge radars designed for larger, faster threats.

Old threats are also re-emerging. China has tested a Fractional Orbital Bombardment System (FOBS), essentially a nuclear-armed satellite that plunges to Earth before completing an orbit, last used by the Soviet Union in 1983. These threats are combining in complex ways: “Future threats will include missile-drone combinations, spaceplanes, aeroballistic missiles, and other hybrids that strain simple categorisation,” argue Tom Karako and Masao Dahlgren of the CSIS think-tank. Israel appears to have used small quadcopters to distract Iranian air defences in April before using a sophisticated air-launched ballistic missile to destroy a radar.

Intercepting these threats economically is another challenge. In the 1980s, Paul Nitze, Reagan’s arms-control negotiator, established the Nitze criterion: a missile-defence system must be “cost effective at the margin”, so adversaries cannot overwhelm defences with cheaper missiles. Today, the ratio is often unfavourable: Ukraine and America have both used expensive interceptors to destroy cheaper Iranian-made drones.

Missile defence advocates counter that any calculation must consider the cost of failing to intercept the missile: the loss of critical infrastructure in Ukraine or the disruption to Red Sea shipping. “On April 14th”, the day after Iran’s barrage, notes Mr Patel, “the stock exchange in Israel continued to work and people went to work on that day.” Nonetheless, the expense is significant. Mr Karako estimates that building layered defences for Guam, a strategically important American island in the Pacific Ocean, would likely cost around $5bn.

🚨Update: US has NO air defenses over our country!! Trump says if elected ‘we will build a great Iron Dome over our country!’ And finally protect the homeland like Biden protects Ukraine and its borders. pic.twitter.com/Jcp1pHXnPd

— US Civil Defense News (@CaptCoronado) June 22, 2024

Cheaper systems often entail greater risk. Wes Rumbaugh of CSIS highlights the USS Gravely’s destruction of an Iranian-made anti-ship cruise missile in the Red Sea in January. The ship used 20mm bullets from its Phalanx cannon—cheap but could only engage the threat once it was dangerously close, within 2km of the $2.5bn ship. The good news is that interceptor costs are decreasing. Between 2018 and 2023, the cost of navy SM-6 missiles—first used in combat in the Red Sea against Houthi drones in December—fell annually in real terms. Lasers, which intercept threats at the speed of light without expending ammunition, are also promising.

More or cheaper interceptors are not the sole issue. “Missile defence is fundamentally a sensing problem,” argues Mr Dahlgren. It is impossible to shoot down what cannot be tracked. However, the same technological advances aiding missile-makers are also helping defenders. Hypersonic gliders are harder to spot because they fly lower and lack bright rocket plumes during their glide phase. One solution is to use falling space-launch costs to place numerous sensors in orbit. Improved infrared sensors might detect the glider heating up from air resistance; radio-frequency sensors might detect the charged plasma created as the glider cuts through the air. It is also becoming easier to process sensor data, says Mr Dahlgren, citing how the North Warning System, a set of American and Canadian radars, has been enhanced with artificial intelligence. International cooperation, such as between Israel and its Arab partners, will become crucial for data collection.

Despite the optimism of Trump and other politicians, no missile shield will ever be impenetrable. Success with short- and medium-range missiles in Ukraine and Israel does not guarantee success against ICBMs. As missiles become cheaper, more accurate, and distributed to smaller countries and armed groups, the threat will grow. Countries will have to choose between protecting civilians, critical infrastructure, military bases, and frontline troops in wartime. The race between missile and interceptor is entering a new and uncertain era.