The Case for U.S. Homeland Ballistic Missile Defense Against North Korea

The United States has long maintained that it can defend the homeland against limited North Korean intercontinental ballistic missile (ICBM) strikes. The 2022 Missile Defense Review (MDR) reaffirmed that the United States “will continue to stay ahead of North Korean missile threats to the homeland” through homeland missile defense, missile defeat, and “the credible threat of direct cost imposition through nuclear and non-nuclear means.” While “missile defeat” destroys North Korean ICBMs before they are launched, homeland ballistic missile defense (BMD) defends the U.S. homeland by intercepting ICBMs after they are launched. Given North Korea’s recent ICBM expansion – it tested the Hwasong-18 in December 2023 – and its policy that places its nuclear forces on “trigger” alert and promotes preemptive nuclear weapons use in response to threats, the need for homeland BMD should not be understated. While some argue that homeland BMD is ineffective and costly and upsets strategic stability with Russia and China, it is necessary to defend against the evolving North Korean threat to the U.S. homeland. 

How Homeland BMD Works

The U.S. homeland ballistic missile defense system is the Ground-based Midcourse Defense (GMD) system that protects all 50 states from limited ICBM strikes. GMD integrates data, via fire control (GFC) and communications systems, from global sensors on land, sea, and space to intercept incoming missiles during their mid-course of flight using the Ground-based Interceptor (GBI). Sensors and satellites detect the incoming missile and send a message to ground-based radar in Alaska, which discriminates between the missile warhead and decoys. The GFC system then sends a message to launch the GBI through secure communications. The interceptor launches, and the Exoatmospheric Kill Vehicle (EKV) separates from the interceptor. The EKV uses sensors to track the incoming missile, and data updates the direction the EKV travels mid-flight. The EKV then physically collides with the incoming missile and destroys it upon impact. Sensors and data finally verify the hit.

There are currently 44 GBIsnited States – 40 at Fort Greely in Alaska and four at Vandenberg Air Force Base in California. The Department of Defense will augment the GBIs with 20 Next Generation Interceptors (NGIs) – advanced technology with multiple kill vehicles atop each interceptor – around 2028.

The Case for Homeland BMD Against North Korea

Homeland BMD augments the credibility of the U.S. nuclear deterrent against North Korea by adding denial to threats of punishment. Homeland BMD prevents limited North Korean ICBM strikes from reaching the U.S. homeland, which adds to the threat of “cost imposition” should North Korea launch a nuclear weapon. Deterrence is strongest when the United States can deny and punish North Korean aggression.

First, homeland BMD protects U.S. cities from limited North Korean ICBM strikes. While experts estimate that North Korea has between 20 and 60 total nuclear weapons, it lacks the ICBM numbers to threaten U.S. nuclear forces. So, it threatens U.S. cities. Estimates suggest North Korea has at most 11 Hwasong-17 ICBMs, based on a February 2023 parade. Using this number, with 44 GBIs, the United States currently has a four-to-one interceptor to ICBM ratio. When the United States adds 20 NGIs to its GMD system in 2028, this ratio will become nearly six to one. Given these favorable ratios, the United States can prevent North Korean ICBM strikes from reaching the homeland. Moreover, the GMD system has proved to be effective. All three GMD tests since 2017, including most recently in December 2023, successfully intercepted ballistic missiles with the Capability Enhanced-II (CE-II) Block I EKV. This demonstrates the improvements made in the GMD system, as only half of all tests before 2017 were successful. Just like any other product in any other industry, research and development pays off.

Second, because the GMD system is effective, homeland BMD complicates North Korean planning by introducing uncertainty about the success of a strike on the American homeland. North Korea’s limited capabilities are highly unlikely to penetrate the GMD system, and this uncertainty deters it from launching a first strike because its strike will be futile (its missiles will not hit the United States) and fatal (the United States will respond overwhelmingly). The 2022 Nuclear Posture Review (NPR) stated that “there is no scenario in which the Kim regime could employ nuclear weapons and survive.” The uncertainty of strike success combined with the certainty of destruction enhances deterrence vis-a-vis North Korea.

Third, homeland BMD prevents “cheap shot” coercion by raising the threshold for North Korean nuclear use. Because the GMD system prevents limited strikes from reaching the U.S. homeland, it increases the number of missiles – likely above what North Korea possesses – needed for a successful strike. This raises the threshold for nuclear conflict, which negates the credibility of a North Korean threat to launch one or two missiles (“cheap shots”) that hit the United States and then threaten to launch more if the United States does not succumb to North Korean demands. The first couple of missiles simply will not penetrate the GMD system, so North Korea cannot coerce the United States with limited strikes.

Fourth, homeland BMD reassures allies that the United States will fulfill its global security commitments. Not only does the GMD system demonstrate physical capability, but it also signals American resolve and commitment to maintaining its deterrent at home and abroad. The 2022 MDR makes it clear that the GMD system offers “a visible measure of protection for the U.S. population while reassuring allies and partners that the United States will not be coerced by threats to the homeland from states like North Korea.” Because the United States takes steps to protect itself and reduce its vulnerability to ballistic missile strikes, it may instill confidence in allies and partners that the United States will run risks on their behalf to protect them from coercive threats. Japan and South Korea should feel protected from North Korean coercion, knowing that the United States has the capability, resolve, and freedom of action to defend them. Indeed, North Korea would not want to strike Japan or South Korea, knowing that the United States will respond overwhelmingly.

Fifth, homeland BMD provides decision-makers additional time in crisis to end conflict at the lowest level. Because global sensors increase warning time, and GBIs prevent limited North Korean ICBM strikes from reaching the U.S. homeland, the GMD system provides decision-makers additional time in crisis to consider less escalatory actions than nuclear strikes. This enables the United States to respond flexibly to end conflict at the lowest level possible.

Sixth, should deterrence fail, homeland BMD limits damage to the U.S. population. The GMD system will intercept limited North Korean ICBM strikes, but if North Korea launched 20-plus ICBMs – which it likely does not have – only a few would hit the United States rather than the entire strike force. Damage limitation protects the U.S. population, preserves American capability and freedom of action, and expands decision-making space for leaders.

Rebuttals and More Rebuttals

The most significant criticism of homeland BMD is that it upsets strategic stability with Russia and China. This belief dates back to the Cold War when scholars believed BMD sparked arms races, hindered arms control with the Soviet Union, and emphasized defense when offense was the main deterrent. Therefore, in the current age, if Russia and China feel that U.S. homeland BMD threatens their nuclear strike success, they will build more delivery systems to evade the defenses and maintain their second-strike capabilities (so, therefore, their nuclear deterrents). This is the “action-reaction” hypothesis. Some see Russia’s development of the Sarmat heavy ICBM, the Kinzhal air-launched hypersonic glide vehicle, and plans for nuclear-explosive anti-satellite (ASAT) weapons as driven by the need to evade the GMD system in Alaska and California. Others see China’s rapid nuclear build-up – estimates of 1,000 warheads by 2030 – as driven by the same motive.

There are a few counters to this criticism. First, simply put, a few dozen interceptors – 44 current GBIs and 20 more NGIs around 2028 – do not threaten Russian or Chinese ICBMs. Russia’s 1,800-plus strategic warheads, including over 1,200 ICBMs, and China’s 400-plus strategic warheads, including over 230 ICBMs, are not ineffective in the face of a few dozen GBIs. Such a massive strike would penetrate the GMD system. Second, the rationale for the first homeland BMD deployment, announced during the Johnson administration in the early 1960s, is similar to today’s rationale for a GMD system. 

Early BMD intended to protect the homeland against the limited threat from China, but not from the Soviet Union. Today, U.S. policy is clear that homeland BMD defends against rogue states (North Korea and Iran) but not Russia or China. The United States relies on strategic deterrence of Russia and China and will continue to communicate this policy. Third, homeland BMD does not, without fail, spark arms races. The largest bilateral U.S.-Russia deployed strategic nuclear arms reductions coincided with expanded U.S. homeland BMD deployment after President George W. Bush withdrew from the Anti-Ballistic Missile (ABM) Treaty in 2002. Ambassador Robert Joseph observed, “While the conclusion of the ABM Treaty in 1972 led to the largest Soviet strategic nuclear build-up in history…the United States withdrawal from the treaty 30 years later was followed by an actual decrease in Russia’s strategic nuclear arsenal.” In terms of China, its rapid arms build-up all at once does not meet the action-reaction hypothesis; if BMD drove its build-up, then China should have built up slowly to mirror the U.S. BMD build-up. 

Fourth, homeland BMD is not, again, without fail, an impediment to arms control. The United States and Russia agreed to the Strategic Offensive Reductions Treaty (SORT) in 2002 after President Bush announced the U.S. withdrawal from the ABM Treaty. Negotiations for the Strategic Arms Reduction Treaty (START I) in 1991 and New START (which superseded SORT in 2011) took place while the United States had homeland BMD. New START limited deployed strategic warheads to 1,550, a greater reduction than SORT, yet the United States still had homeland BMD during negotiations. In fact, today’s GMD system is less than one-quarter of the original interceptor limit (200 interceptors) enshrined in the 1972 ABM Treaty.

Another criticism is that homeland BMD is ineffective and costly. However, all three GMD tests since 2017 have proven the opposite. The system is effective. Moreover, in November 2020, the United States successfully tested the Standard Missile-3 (SM-3) Block IIA against an ICBM. Though part of the regional Aegis BMD system intended to intercept shorter-range ballistic missiles, the SM-3 Block IIA proved it could intercept ICBMs and provide an additional layer (“underlay”) to the GMD system. In terms of cost, the U.S. Department of Defense (DoD)  requested $28.4 billion for its missile defense and defeat programs in Fiscal Year (FY) 2025, which is about 3% of the total $850 billion DoD budget. Of that $28.4 billion, only $2.5 billion was requested for the GBI and NGI systems, which is about three-tenths of a percent of the entire DoD budget. In context, the GMD system is quite affordable.

Protection, Deterrence, and Reassurance

The U.S. homeland BMD system against North Korea is effective and affordable. It does not inevitably provoke arms races nor hinder arms control. Instead, it enhances the credibility of the American deterrent against North Korea by adding denial to threats of punishment. Homeland BMD is the best option for staying ahead of the evolving North Korean nuclear threat. 

Views expressed are the author’s own and do not represent the views of GSSR, Georgetown University, or any other entity. Image Credit: Breaking Defense