An animation from the U.S. Missile Defense Agency shows the steps involved in intercepting and destroying and intercontinental ballistic missile.

Earlier this week, during the 8th congress of the Workers’ Party in Pyongyang, North Korea, as reported by North Korea’s Central News Agency, Kim Jong Un referred to the U.S. as “our biggest enemy” and outlined plans to upgrade the country’s nuclear forces, develop hypersonic weapons and solid-fuel intercontinental ballistic missiles, and build the ability to strike targets out to 15,000 kilometers, which would encompass the entire United States.

The Party meeting culminated with North Korea unveiling a new submarine-launched ballistic missile, which it termed the “world’s mightiest.” This is on the heels of a parade last October, when North Korea unveiled a new ICBM — its largest ever.

We shouldn’t be surprised. These development efforts are consistent going back to at least December 2011, when Kim Jong Un succeeded his father as the leader of North Korea.

The ballistic missile threat to our homeland is real, and we need a continual dialogue on how to address it, including a layered approach. How much missile defense should we pursue when, as a department, we have many defense requirements and are faced with a flattening budget? This will be an important discussion in the coming year, as in the fiscal 2021 National Defense Authorization Act, Congress has directed the Defense Department to develop and report requirements for a proposed layered homeland defense architecture.

As a young naval officer during the Cold War, in studying my profession, I learned basic naval tactics including defense in depth. In every warfare area, it is best to establish defenses against any threat at extended ranges to give you multiple opportunities to defeat it all the way through point defense — the last-ditch effort before you suffer significant damage.

The more complex the threat, the more advanced options you wanted at your disposal to counter it. It would be irresponsible if leaders did not strive for some defense in depth, particularly if the lives of U.S. citizens are at stake. This is especially true in homeland missile defense, when the missile threat is growing in number and capability.

While we are confident we can defend the homeland against today’s missile threats from North Korea, the future threat foretold by Kim Jong Un this month is dynamic and, when you factor in Iran, unpredictable. Launch after launch, test after test, these potential adversaries are learning, adapting and improving their capabilities. Iran is gaining valuable information and learning from its space-launch program, which contributes directly to an effort to develop an ICBM, should it choose to do so.

See a US warship shoot down an ICBM

See the U.S. Missile Defense Agency and Navy sailors aboard the destroyer John Finn intercept and destroy a threat-representative ICBM target with an SM-3 Block IIA missile.

Just as adversaries are adapting their missile capabilities to suit their objectives, we too must adapt our missile defense posture to stay ahead of the threat, address potential aggression and diminish any perception that a strategy based on the threat of long-range ballistic missiles could succeed.

If we do not adapt, we become vulnerable to coercion by the mere threat of attack, which would significantly complicate our relationships and credibility with allies and partners, and limit our options during a crisis. Stronger, reinforced defenses give us leverage that enables our leaders and diplomats to more effectively negotiate disputes.

A number of programs are in various stages of maturity and progress to stay ahead of the threat now and in the future. Today, the United States has 44 Ground-Based Interceptors, which undergo regular testing and performance upgrades to ensure they are reliable and can pace an evolving and more challenging ballistic missile threat consisting of countermeasures, like decoys. The Next Generation Interceptor, when fielded between 2028 and 2030, will introduce at least 20 more capable missiles to enhance the defense of the United States.

To augment Ground-Based Interceptor capabilities and provide a complementary layer of protection between now and 2028, the Missile Defense Agency recently conducted a successful intercept test with an SM-3 Block IIA — originally designed to engage medium- or intermediate-range threats — against an ICBM-class threat; a wonderful and important achievement by the MDA and the Navy. As the SM-3 IIA missile can be ship- or land-based, the United States now can explore options for it to supplement the homeland defense mission, adding defense in depth. The benefits to this potential addition are extremely important.

By adding capability and depth, U.S. missile defense becomes more effective and therefore more credible, adding a level of uncertainty to any adversary’s calculus of a successful attack, which has a deterrent value. This added credibility is also an insurance policy should diplomacy and deterrence fail — read “North Korea” — thereby strengthening diplomatic leverage. And it addresses any perception by regional players that any form of appeasement may be required to mitigate the threat. This is the complex nature of any deterrence construct.

Where do we go from here? We should consider testing an upgraded version of the Army’s Terminal High Altitude Area Defense missile system, or THAAD, to determine if it can also contribute to the mission (likely in the important terminal phase of a ballistic missile’s flight). The threat is only becoming more stressing and complex, and we need to gain a deeper understanding of, evolve and maximize the capabilities in our current systems. This is in fact true for all mission areas, but particularly for the most stressful areas like ballistic missile defense. It is also prudent in an era of flattening budgets.

To be clear, I am not advocating to integrate Aegis ships and THAAD as primary players in national missile defense. Their primary mission will always be in support of the joint force forward conducting the full spectrum of day-to-day and contingency operations. However, when the U.S. homeland is threatened, they could function as an important supplement, adding depth, improving deterrence and, should deterrence fail, increasing the probability of a successful defense.

Critics will claim that U.S. efforts to diversify its homeland missile defenses are destabilizing and will cause an arms race with China and Russia — a critique routinely echoed by officials in Beijing and Moscow but not supported by basic mathematics. Sixty-four interceptors is not nearly enough to counter the hundreds of advanced ICBMs (carrying more than 1,000 nuclear warheads) that Russia maintains, nor China’s rapidly growing inventory of intercontinental-range systems expected to grow to 200 by 2025. But it could be enough to mitigate a less capable threat like North Korea and potentially Iran, if supplemented by other systems such as the SM-3 Block IIA.

These facts, however, do not prevent Beijing and Moscow from engaging in disinformation campaigns to pursue their national interests, fuel missile defense critics, and discourage cooperation in our alliances and partnerships. While China and Russia claim duplicitously that U.S. missile defenses are destabilizing, both countries are currently building their own missile defenses against a range of threats.

For example, Russia is upgrading its ballistic missile defense system around Moscow — whose 68 interceptors are nuclear-tipped, unlike U.S. conventional interceptors. China is also developing its own indigenous missile defense systems for defense of its homeland; and as stated in its 2019 Defense White Paper, the People’s Liberation Army Air Force is “improving its capabilities for strategic early warning, air strikes, [and] air and missile defense.”

In this photo taken from undated footage distributed by Russian Defense Ministry Press Service, an intercontinental ballistic missile lifts off from a truck-mounted launcher somewhere in Russia. (Russian Defense Ministry Press Service via AP)
In this photo taken from undated footage distributed by Russian Defense Ministry Press Service, an intercontinental ballistic missile lifts off from a truck-mounted launcher somewhere in Russia. (Russian Defense Ministry Press Service via AP)

It is obvious that Russia and China believe that cheap and relatively easy disinformation campaigns against U.S. missile defenses have the chance of producing sizable benefits: stirring up U.S. public dissent, dividing alliances and ultimately leaving the U.S. homeland more vulnerable to their missile-based coercive strategies. But the United States will not abandon its most fundamental duty: to defend its citizens from the threat of foreign attack.

Layered homeland missile defense represents the opportunity to support diplomacy and deterrence — and, should both fail, provide for an effective defense. As the threat continues to grow and evolve, we should continue to pace it by maximizing the variety of our systems that can contribute to defeating it. Ultimately, the United States must strive for credible missile defense options across the threat trajectory, from launch, boost, midcourse and through the terminal phases.

Let me conclude with one fairly recent real-world example to place the importance of homeland missile defense in proper context. I was living in Hawaii on Jan. 13, 2018, when many in the state received a text message: “Emergency Alert: Ballistic missile threat inbound to Hawaii. Seek immediate shelter. This is not a drill.” Recall that during the preceding months from August through November 2017, North Korea tested a number of high-performance ballistic missiles, two of which flew over Japan and landed in the Pacific Ocean, so there was already an element of anxiety on the islands.

The emergency alert was a mistake caused by the inadvertent pressing of a button at the Hawaii Emergency Management Agency. But in the 38 minutes before word was finally put out about the mistake, residents were scrambling to take shelter amid a general feeling of helplessness, while some Navy ship commanding officers were preparing to get their ships underway to keep them safe at sea during the attack. Had our Aegis destroyers been armed with the SM-3 Block IIA, they would have been able to do more than just avoid the attack: The ships already at sea could’ve provided a significant layer to the defense of Hawaii, which is our homeland.

The successful SM-3 Block IIA test — which was a “defense of Hawaii” scenario — demonstrated that we are not and should not be complacent. We should continue to do more to responsibly add defense in depth of our homeland against today’s and tomorrow’s rogue ballistic missile threats. A secure U.S. homeland is the most powerful foundation on which we can build toward a more peaceful and less risky future for the American people.

Vic Mercado is the U.S. assistant secretary of defense for strategy, plans and capabilities.