In 2017, I helped author the CSIS report “Missile Defense 2020,” a broad look at the history, status and future of the U.S. homeland missile defense system known as Ground-based Midcourse Defense. The report argued that the establishment of GMD had put the United States in an advantageous position relative to the North Korean missile threat, but this advantage would be short-lived if the United States failed to improve GMD through incremental milestones and regular testing. GMD has had some notable achievements with this strategy. The Pentagon, however, seems to be moving away from this proven approach to GMD, attempting great leaps rather than manageable steps. This riskier approach could make the United States less secure over the near and long term.

Until recently, GMD had been following a well-defined road map, with good results. After a series of flight-test failures from 2010-2013, the Missile Defense Agency began a rigorous effort to root out anomalies within the system’s Ground-Based Interceptors, or GBI. MDA carried out a successful intercept in 2014, followed by intercepting an intercontinental ballistic missile-class target for the first time in 2017. In 2019, GMD engaged an ICBM target with a salvo of two GBIs, marking another first for the system. MDA also expanded the fleet to 44 GBIs and is constructing a new Long Range Discrimination Radar in Alaska to provide the system much-needed sensor support.

These achievements were supposed to be followed by an incremental modernization of the GBIs. The plan was to incorporate a new Redesigned Kill Vehicle around the year 2020. The RKV would be similar in concept to those currently deployed but incorporate new technologies and nearly 20 years of lessons learned.

Another part of the plan was to give the GBIs a new booster, one that gave the war fighter the option of using either two or three stages, thereby providing the system more time and space to engage incoming missiles.

MDA also set its sights on a set of longer-term objectives. These goals included a space-based sensor layer for tracking missile threats, and a GBI equipped with multiple kill vehicles that would greatly expand the capacity of the GBI fleet. While the volume kill concept had great appeal, MDA recognized the need for a developmental step between the current kill vehicles and a more advanced, unproven concept. Historically, U.S. missile defense has done best when pursuing steady, achievable goals. The highly successful Aegis Ballistic Missile Defense program, for example, has consistently adhered to the mantra: “Build a little, test a little, learn a lot.”

The RKV program, however, ran into delays. Yet, rather than continue trying to fix the program, the Pentagon opted to abandon it and skip directly to a more advanced, multi-kill vehicle approach called the Next Generation Interceptor.

NGI is an ambitious, 10-plus year endeavor that carries significant risk. In the near term, it means that the president’s goal to add 20 more GBIs to the fleet will go unmet, as those GBIs were supposed to be capped with RKVs. Any expansion to the GBI fleet before 2030 will require the design and construction of a modernized unitary kill vehicle of some kind.

Absent any effort to expand or modernize the GBI fleet, homeland missile defense will likely fall behind the North Korean missile threat while NGI matures over the next 10 years. The decline will increase U.S. vulnerability to coercion by North Korean leader Kim Jong Un at a time when the U.S. military is scrambling to address Chinese and Russian aggression. Furthermore, a major delay of NGI a decade from now (or worse, a failure for NGI to materialize at all) would leave the United States with a fleet of GBIs falling rapidly into obsolescence, squandering decades of resources and effort.

To be clear, the United States should continue developing NGI. Missile threats to the U.S. homeland continue to grow at an alarming pace, in quantity and complexity. But the Pentagon and Congress should support these longer-term efforts while still investing in nearer-term options that keep U.S. homeland defenses current to North Korean missile capabilities, hedge against NGI failure and preserve U.S. investments in the GMD system.

A potential path forward may lie in the Senate’s version of the fiscal 2021 National Defense Authorization Act, which contains draft language that would require the deployment of 20 additional GBIs equipped with an interim, unitary kill vehicle by 2026.

Three years ago, we titled our study of GMD “Missile Defense 2020” because we believed that this year would be the start of a new chapter in U.S. homeland missile defense. Obviously, much has changed with the cancellation of RKV. Yet, despite all its challenges, this year may still provide the opportunity to make the kind of decisions that will strengthen our national security in the near and long term.

Ian Williams is a fellow in the International Security Program at the Center for Strategic and International Studies, where he also serves as deputy director of the Missile Defense Project.

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