The head of U.S. Indo-Pacific Command said last week his top priority is establishing an Aegis Ashore system on Guam by 2026. New air defenses will help protect U.S. citizens and forces in Guam; but as Japan’s government found, Aegis Ashore may not be the best option to protect military and civilian targets from growing and improving Chinese and North Korean missile threats.
Guam is pivotal to U.S. and allied military posture in the Western Pacific. Home to Andersen Air Force Base and Apra Harbor, it is far enough from adversaries like China and North Korea to negate the threat from more numerous short-range missiles but close enough to support air and naval operations throughout the Philippine Sea and South and East China seas.
Although the current Terminal High Altitude Area Defense battery on Guam can defend against some ballistic missiles, its single AN/TPY-2 radar is vulnerable and cannot provide 360-degree coverage. Moreover, THAAD’s focus on high altitudes makes it a poor fit to defeat lower-flying aircraft or cruise missiles that would likely be used by China’s military against Guam. The island needs a new air defense architecture.
Aegis Ashore is highly capable, but has its own limitations. Designed primarily to counter small numbers of ballistic missiles, its fixed missile magazine and radar would be vulnerable to attack and would fall short against the bombardment possible from China.
Instead of installing one or more Aegis Ashore systems on Guam, a more effective air and missile defense architecture would combine the latest version of the Aegis Combat System with a disaggregated system of existing sensors, effectors, and command-and-control nodes. A distributed architecture would also be scalable, allowing air and missile defenses to also protect U.S. citizens and forces operating in the Northern Marianas.
Guam’s geography enables longer-range sensing than would be possible from a ship or a single Aegis Ashore radar. Fixed, relocatable and mobile radio frequency sensors should be positioned around the island’s perimeter, such as compact versions of SPY-6 or Lower Tier Air and Missile Defense Sensor radars and the passive Army Long-Range Persistent Surveillance system. During periods of heightened tension, passive and active radio frequency and electro-optical/infrared sensors could also be deployed on unmanned aircraft and stratospheric balloons to monitor over-the-horizon threats. This mixed architecture would provide better collective coverage and be more difficult to defeat compared to one or two fixed Aegis Ashore deckhouses.
To shoot down enemy missiles and aircraft, the architecture should field mobile, containerized launchers for long-range interceptors like the SM-6 and SM-3 rather than Aegis Ashore’s finite and targetable in-ground vertical launch magazines. They should be complemented by medium- to short-range engagement systems to protect high-value targets such as the Patriot, the National Advanced Surface-to-Air Missile System or the Army’s planned Indirect Fire Protection Capability, as well as non-kinetic defenses such as high-powered microwave weapons and electronic warfare systems that could damage or confuse the guidance systems on incoming missiles.
Today, destroyers patrol the waters around Guam to provide ballistic missile defense capacity beyond that available with THAAD. A new distributed architecture would place more capacity ashore to free surface combatants from missile defense duty. In a crisis or conflict, the architecture could add capacity with surface action groups and combat air patrols capable of intercepting threats at longer ranges.
Instead of Aegis Ashore’s large, single C2 node, a distributed architecture would virtualize the Aegis Combat System to allow multiple facilities or mobile vehicles to serve as miniature air operations centers. The mobility of sensors, effectors and C2 nodes in this architecture would enable the employment of camouflage, concealment and deception, including decoys, to complicate enemy targeting and increase the number of weapons needed to ensure a successful attack.
INDOPACOM’s plan for implementing new Guam air defenses should also apply lessons from Japan’s aborted Aegis Ashore program, whose accelerated timeline contributed to the selection of the least expensive and technically risky option — two fixed Aegis Ashore systems — and the discounting of alternatives. Adm. Phil Davidson’s 2026 goal of improving Guam’s defenses faces a similar risk.
Bound by an iron triangle, Guam’s air and missile defenses can be good, fast or cheap — but not all three. If 2026 is held as a rigid constraint, the only solution able to meet the schedule and requirements may be the familiar, and ineffective, fixed Aegis Ashore architecture.
Compared to one or two Aegis Ashore sites, a distributed architecture may require slightly more time to develop or funds to field. But a phased approach could introduce new systems as funding becomes available and allow expanding the system’s capability to meet the evolving threat. For example, SPY-6 radars, C2 bunkers and composite THAAD-Patriot-NASAMS batteries could be fielded before 2026, quickly followed by the introduction of mobile assets.
Guam and the Northern Marianas are essential to U.S. strategy and operations in the Western Pacific. Their defenses have long been ignored, and Adm. Davidson should be lauded for charting a path forward. A disaggregated architecture, however, will be more likely to realize INDOPACOM’s vision of resilient and scalable air and missile defense.
Timothy A. Walton is a fellow at the Hudson Institute’s Center for Defense Concepts and Technology, where Bryan Clark is a senior fellow.