As boost-phase defenses become viable, they could reduce the destabilizing effects of longer-ranged defenses on great-power relationships.
It is a curious feature of nuclear strategy that anti-missile systems that deter rogue states also destabilize relations among major powers. But new technology, combined with intensive diplomacy, may offer a way out of this trap.
Let’s start with reviewing how ABM systems are destabilizing. An ideal mutually-assured-destruction scenario — forgive the absurdity — confers no advantages to the nation that shoots first. Sure, a first strike might knock out a good number of nuclear installations, but the remaining arsenal would still be more than capable of delivering annihilation. This means decision-making under pressure is relatively straightforward: don’t fire nuclear weapons first. No matter how suspicious you are of your enemy, restraint always offers a chance for survival. A first strike guarantees your own destruction.
However, when you throw ABM systems into the mix, the situation grows considerably murkier. With sufficient defenses, a nation might just be able to stop (or at least blunt) a weakened second strike. This changes the calculus completely. If confronted with a possible enemy strike, leaders may feel they have no choice but to fire pre-emptively and take their chances at defending against a second strike: “Nuclear war should be avoided, but if you’re going to have one it’s best to shoot first.”
This logic led Nixon and Brezhnev to sign the 1972 Anti-Ballistic Missile Treaty, limiting the number of anti-ICBM missiles to a paltry 100 each. Three decades later, George W. Bush withdrew from the agreement, citing the (then-potential) threat from North Korea and (still-only-potentially) Iran. If Pyongyang could develop long-range missiles, then it could invade South Korea while threatening a nuclear strike on the U.S. mainland. Would the United States risk Los Angeles or San Francisco to come to Seoul’s aid? Bush argued that ABMs were needed to protect the United States and allies alike.
But as these systems deployed — THAAD to South Korea, Aegis Ashore to Europe, Ground Based Midcourse Defense to Alaska and California, and the Navy’s Aegis Ballistic Missile Defense on the world’s oceans — China and Russia grew increasingly alarmed. These systems may be primarily aimed at North Korea and Iran, but with enough improvement, they might eventually be used to stop (or blunt) a superpower’s second strike.
Russia’s concerns can be seen in its recent proliferation efforts. It has recently announced new hypersonic missiles that can theoretically penetrate any missile defenses and deployed 9M729 missiles on land, violating the INF treaty. China will likely also look to bolster its arsenal if it sees its nuclear forces as increasingly ineffective against U.S. missile defense schemes. So, by seeking to protect itself against smaller, hostile states, the United States is igniting an arms race among the more powerful nuclear states. Or is there another way?
Today’s missile defenses target incoming weapons in their midcourse or terminal phases, thanks largely to technical challenges that have ruled out interception during the boost phase. This phase only lasts a short time, so the interceptors must be positioned close to the launch area and ready to fire instantly.
However, with recent advances in laser technology and networked communications, viable boost-phase defense is within reach. Lockheed is slated to deliver a 60-150-kilowatt laser for integration with the Aegis system by 2020. An earlier 30-kilowatt model has shown the ability to shoot down drones and disable a truck from a mile away. Indeed, the Defense Department’s 2019 Missile Defense Review says, “Developing scalable, efficient, and compact high energy laser technology holds the potential to provide a future cost-effective capability to destroy boosting missiles in the early part of the trajectory.” Lasers have the advantage of near-instantaneous time to target and are not limited by the number and cost of interceptors. Also mentioned is the possibility of arming F-35s with interceptors, made possible by the improving network-centric coordination of targeting information across multiple platforms.
Boost-phase defenses help solve at least one tactical problem: MIRVs, or Multiple Independently-Targetable Reentry Vehicles, long the bane of ABM developers. Within a few minutes of launch, a MIRV-equipped missile can send its warheads and dummies off on different trajectories. The best way to deal with this is to hit the missile before one target becomes ten.
But boost-phase defenses offer a key strategic advantage as well. They can, and indeed must, be placed close to their targets. Their batteries would be able to intercept North Korean missiles but not launches from deep within mainland China and unlike current forward-deployed regional systems, they can have verifiably limited ranges. China is currently up-in-arms over the deployment of THAAD in South Korea, while Russia is livid about the placement of Aegis batteries in Romania and Poland. As terminal-phase and midcourse-phase systems, these are inherently long-range. THAAD interceptors have a range of over 200 kilometers, while an Aegis-fired SM-6 can fly as many as 240 kilometers. The THAAD-ER and SM-6 IIB upgrades only extend these ranges. On the other hand, a Sidewinder fired from an F-35 has a maximum range of about 35 kilometers. For the foreseeable future, atmospheric lasers will be similarly short-ranged.
This also provides a solution to China’s other gripe with the placement of THAAD: that the accompanying radar system penetrates deep into Chinese airspace. Large radar ranges are a necessary component of any midcourse or terminal-phase system. If THAAD is going to intercept a ballistic missile 200 kilometers out, then it needs to launch the interceptor long before then, and it will need to acquire the missile even further out. As such, the AN/TPY-2 radar that accompanies the THAAD system has an estimated range of at least 1,000 kilometers, which could reach from Seoul to Beijing and would allow the United States to monitor all activity in that part of Chinese airspace. However, boost-phase defenses work on the principle of targeting missiles inside a predetermined area. Therefore, they can use less powerful, more localized radars focused just on North Korean ICBM sites rather than the whole region.
But a technology change alone isn’t enough to extract the United States from its security dilemma; that will require trust and communication. U.S. officials must take the initiative to convince Russia and China that these systems are not aimed at them. Boost-phase defense provides the technical basis for this, but it must be accompanied by openness and transparency. This could include allowing inspections of missile defense installations to verify their short-ranged nature. Unfortunately, current diplomatic trust is not high, as shown by the collapse of the INF treaty. The situation is further hindered by statements such as President Trump’s words at the Missile Defense Review rollout: “Our goal is simple. To ensure that we can detect and destroy any missile launched against the United States anywhere, anytime, anyplace.”
As ABM technology improves, especially the effectiveness of lasers, the United States would do well to focus on localized, surface-based, boost-phase defenses rather than attempting to build a massive Reagan-style missile defense scheme that would serve only to destabilize the current world order. This will provide an effective defense against current and future rogue states, while maintaining the status quo among the major nuclear powers.