Next week, people from across the missile defense community will gather at an annual symposium in Huntsville, Alabama, to consider how to adapt U.S. missile defense efforts to the challenge of renewed competition with Russia and China. A centerpiece of their discussions will be the emergence of advanced hypersonic missile threats and what to do about them.

Over the past few years, the Pentagon has prioritized the development of offensive hypersonic strike weapons, with billions of dollars in contracts already awarded for each of the major military services to acquire hypersonic strike missiles of their own.

The counter-hypersonic mission, however, received surprisingly short shrift in recent defense budgets, with progress on hypersonic defense thus far piecemeal and halting. Some leading military officials charged with procuring hypersonic strike missiles have said that defending against hypersonic missiles is too hard, so we shouldn’t even try.

That short-sighted approach is at odds with the vision of newly confirmed Secretary of Defense Mark Esper, who stated to Congress that he will advocate hypersonic missile defense, to include the development of new sensors, interceptors, and advanced command-and-control systems.

Public commentary on hypersonic threats has been somewhat hyperbolic. Yes, hypersonics are fast — five or more times the speed of sound — but that’s slower than many ballistic missiles. Aerodynamic maneuver makes for a less predictable flight path, but this also means that atmospheric friction would remove the kind of decoys that might accompany a ballistic reentry vehicle. Whether a boosted glide vehicle, a scramjet cruise missile or a maneuverable quasi-ballistic missile, hypersonics pose a complex air defense challenge, but they are not invulnerable.

The strategic significance of hypersonics is nevertheless quite real. Today’s Patriot, Terminal High Altitude Area Defense and Aegis defenses protect American carrier groups and ground forces against aerial and ballistic missile attack. Designed to go around or under those defenses, hypersonics are a more sophisticated means to hold forces at risk, and thereby undermine our broader defense goals and alliance system. Even if the United States catches up with the Chinese and Russians on hypersonic strike, our adversaries’ ability to hold U.S. carriers and forward bases at risk will push back U.S. forces. They could certainly also be used to target the American homeland, but the more urgent threat is regional. Passive defense only goes so far — ships can only go so fast, and air bases cannot be moved. Active defenses must be part of a balanced strategy.

The first priority here is a space sensor layer. Unlike ballistic missiles, hypersonic missiles fly at lower and changing altitudes, are harder to see, and travel an uncertain flight path. Current early warning satellites can detect the launch of boost-glide vehicles but are unsuited to tracking them during the glide phase. Today’s surface-based ballistic missile radars would only be able to spot a weapon once it crosses the horizon. Only space sensors can provide birth-to-death, fire-control quality tracks for hypersonic missiles.

Unfortunately, recent budget requests have been rather tepid in their commitment to space sensors. The administration’s 2020 request virtually divested the program, and for the second year in a row the Missile Defense Agency listed the space sensor layer as its No. 1 unfunded priority. Thankfully, Congress seems to be in the process of restoring $108 million to return the program to the MDA to move out on development this year.

The second element of hypersonic defense is interceptors. Although existing interceptors may well be improved, Secretary Esper has affirmed that new interceptors will have to be developed that are better suited to the mission’s stressing thermal and high-maneuver environment. The MDA’s third-highest unfunded priority for 2020 — $720 million for hypersonic defense — seems unlikely to be restored this year, but should be restored in the 2021 budget. Directed-energy weapons could potentially target hypersonic threats in their cruise phase or jam them in their terminal phase, but the mission’s complexity will almost certainly require both kinetic and nonkinetic effectors.

The most challenging element will be developing a command-and-control architecture that ties everything together. A long-range hypersonic glide vehicle of significant range could cross continents and multiple combatant commands. Even with better interceptors and an adequate sensor layer, information and fire-control solutions must be developed and rapidly passed to commanders. The Command and Control, Battle Management, and Communications network that supports the Ballistic Missile Defense System may be the foundation of such an architecture, but more dramatic upgrades will be required.

The advent of the hypersonic era is central to the efforts by Russia and China to counter U.S. power projection in the world. The Pentagon’s recent focus on hypersonic strike is necessary but insufficient. It falls now to congressional leadership and those assembling the 2021 budget to rebalance it with a more appropriate mix of hypersonic strike and defense.