In the wee hours of Nov. 17, as Americans slept, the U.S. Navy and the Missile Defense Agency successfully shot down an intercontinental-range ballistic missile using the Navy’s Standard Missile SM-3 Block IIA interceptor launched from a Navy destroyer. This was a spectacular success for national defense for multiple reasons.

Until now, the United States has only tested its ability to defend the homeland from incoming missile attacks with the Ground-based Midcourse Defense system. This system consists of 44 ground-based interceptors deployed in Alaska and California, poised to intercept incoming missiles in their midcourse phase as they fly through space before reentering the atmosphere.

It is U.S. policy to defend the homeland from rogue threats—such as North Korea, which is aggressively advancing its nuclear forces to threaten the United States, and potentially Iran, which continues to improve both its nuclear and ballistic missile capabilities.

Gen. Terrence O’Shaughnessy, former commander of U.S. Northern Command, certified to the U.S. Senate earlier this year that the Ground-based Midcourse Defense system can defend against the North Korean threat today—but the future is less certain. Two main factors drive this uncertainty.

First, the North Korean threat is visibly advancing. One need only recall the North Koreans’ recent display of their new “monster” intercontinental-range missile in a parade last month. But we don’t know much beyond that. How big will North Korea’s long-range missile force be in five years? At what point can North Korea overwhelm our fleet of 44 ground-based interceptors?

Second, the fate of the Ground-based Midcourse Defense system is uncertain. The Pentagon is pursuing the Next-Generation Interceptor program to both increase the capacity of our missile defense system to 64 interceptors and eventually replace our current interceptors, which are old.

The Missile Defense Agency aims to begin fielding the Next-Generation Interceptor by 2028, but it would be naïve to assume such an acquisition program would be free from risk of delay.

Enter the SM-3 Block IIA interceptor. In its 2020 budget request, the Pentagon proposed development of a homeland defense “underlay”—a second layer of interceptors that can take a shot at incoming missiles if our Ground-based Midcourse Defense system’s interceptors miss. The SM-3 Block IIA interceptor can launch from Aegis-equipped Navy destroyers or from Aegis Ashore missile defense systems, and is designed to intercept theater-range missiles.

The Missile Defense Agency and the Navy accomplished a remarkable feat with this intercept, marking the first use of a theater-range, ship-launched interceptor to shoot down a long-range missile. The Heritage Foundation was one of the first to recommend the use of the SM-3 against ICBMs back in 2011.

If SM-3 Block IIA interceptors can defend against ICBMs, then the United States can potentially deploy them as a ‘hedge’ against impending uncertainty in homeland defense. Tuesday’s successful test marks the first step toward operationalizing this capability.

Having cleared this first test with a simple ICBM target, the Missile Defense Agency can proceed with a test against a more complicated ICBM target, potentially armed with decoys or other missile-defense countermeasures.

The next administration will then have many questions to answer about the employment of the SM-3 interceptor to defend the homeland. Its use can be as simple as maintaining the ability to deploy Aegis ships armed with these interceptors to the Pacific in the event of brewing North Korean aggression.

In addition to providing an extra defense of the American people against a North Korean attack, the presence of these ships can boost deterrence. By lowering the probability that an attack will succeed, the presence of U.S. missile defenses complicates an adversary’s attack calculus, forcing countries like North Korea to think twice before pushing the nuclear button.

The next administration could also pursue a series of Aegis Ashore deployments across the United States to establish a permanent SM-3 Block IIA intercept capability.

This longer-term option would require more resources and a concerted effort from the Pentagon. The onus will be on the Pentagon  to “show its math” to members of Congress, who will need to know how many Aegis Ashore systems would need to be built, and where.

This test may provoke blowback from the Russians and Chinese, who claim that advancing U.S. missile defenses will threaten that strategic stability with the United States set by the doctrine of mutually assured destruction. Such accusations must be dismissed as folly.

Despite what they will charge, an underlay of SM-3 interceptors simply cannot defend against Russia’s and China’s advanced arsenals, whose sizes alone can overwhelm U.S. homeland defense. Especially as Russia and China hypocritically advance missile interceptors of their own, the United States must not let Russia and China have a say in our pursuit of an underlay to improve defense against North Korea.

As preparations take place for the next administration and a new Congress, homeland missile defense must remain a top priority. With the success of this test, pursuing the SM-3 Block IIA interceptor as an additional means of homeland defense is now a potential path toward a stronger homeland defense.