sentinel

The first full deployment of the U.S. Army’s new Sentinel A4 air defense radar will be in the area around Washington, D.C., also known as the National Capital Region (NCR). The A4 variant offers a significant boost in capability over preceding versions, especially for spotting and tracking lower and/or slower flying targets like cruise missiles and drones.

An Army officer discussed the capabilities of and plans for the road-mobile Sentinel A4, the formal designation of which is AN/MPQ-64A4, with Secretary Pete Hegseth during a show-and-tell at Redstone Arsenal in Huntsville, Alabama, this past weekend. Members of the media were also present. Hegseth conducted several engagements in the Huntsville area during his trip, which was primarily centered on a ceremony marking the designation of the arsenal as the new headquarters for U.S. Space Command (SPACECOM).

“The plan is to be in full-rate production [of the Sentinel A4] at the end of FY 26 [Fiscal Year 2026], sir, and our first fielding will be actually in the National Capital Region,” the Army officer told Hegseth, as can be heard in the video below. “In January, we’re sending a Sentinel A4 to the National Capital Region to start that immigration process earlier, so that when it is fielded late next year, we’re ready to go.”

War Sec. Pete Hegseth Visits The New Site For U.S. Space Command Headquarters In Huntsville, Alabama

The officer noted that the Army already has a Sentinel A4 radar in South Korea, representing an early operational capability. The deployment to the Korean Peninsula has already been providing valuable feedback for the planned full fielding of the sensor in the NCR next year. You can read more about what is known about the air defense network already in place in the NCR, which includes National Advanced Surface-to-Air Missile Systems (NASAMS) and Avenger air defense systems, as well as a wide array of sensors, in previous TWZ reporting. Existing variants of Sentinel are already regularly used in combination with NASAMS and Avenger.

In terms of the Sentinel A4’s capabilities, “what this radar does is provide 360-degree air surveillance, day or night, [in] adverse weather conditions and the most harsh environments, … [to] identify, track and classify cruise missiles, rotary-wing [aircraft], fixed-wing [aircraft], [and] UAS [uncrewed aerial systems],” the officer explained to Hegseth. It also has the ability to spot and track incoming artillery rockets, shells, and mortar rounds.

Sentinel A4: Bringing Next-Gen Radar Capability to the U.S. Army and Allies

The officer said that many of its more specific capabilities are classified. They did say that it offers a 75 percent increase in detection range over the previous AN/MPQ-64A3, and the ability to track many more targets simultaneously. Much of this is a product of the new active electronically scanned array (AESA) found on the Sentinel A4. As a general rule, AESA radars offer improvements in terms of range, fidelity of tracks, resistance to countermeasures, and overall situational awareness compared to mechanically-scanned types. Depending on how the array itself is configured, AESAs can also perform a much wider array of functions at once.

The Sentinel A4 “does have growth potential,” the Army officer highlighted to Secretary Hegseth during the event. “The current array that you see here is 60 percent populated, but we do have the ability to increase how much is in the array, which allows us to meet future threats.”

That the Sentinel A4’s true operational debut is set to be in the NCR is unsurprising, given the extreme importance of defending the skies over and around Washington, D.C. This is already by far the most heavily monitored and densely defended airspace in the United States.

At the same time, the U.S. military, as a whole, has made no secret of its growing concerns about drone and cruise missile threats, which are very much reflected in the new capabilities found on the new A4 variant of Sentinel.

There has been a particular surge in reported drone incursions over key military facilities and critical non-military infrastructure in the United States in recent years, a trend that is also being observed globally. TWZ has been the first to report on many such incidents. There are questions about the validity of a significant number of these reports, especially given the overlap with claimed sightings of so-called unidentified Aerial Phenomena (UAPs; previously referred to more commonly as unidentified flying objects). Still, the threats posed by drones, including small weaponized commercial types, are very real, and are only set to continue to expand in scale and scope, as TWZ has been calling attention to for years.

Cruise missile threats have also long been top of mind for the U.S. military, including in the context of preparing for potential attacks on the U.S. homeland. The increasing fielding of more capable cruise missiles, such as ones with stealthy features and/or hypersonic speeds, among near-peer competitors like China and Russia, as well as smaller adversaries, has further fueled those concerns.

It’s also worth noting that the NCR has seen a number of false alarm air defense scares over the years. Increased detection capability and general improved situational awareness could help with preventing, though not eliminating, such incidents in the future.

All this being said, the aerial threat ecosystem extends beyond the NCR, and the new capabilities offered by the Sentinel A4 radar will be relevant to Army operations globally. The service has plans to significantly expand its overall air defense force structure in the coming years.

It is possible that plans to send the Sentinel A4s to the NCR, specifically, also presage the deployment of other new air defense capabilities to the area. Sentinel radars are a primary sensor for the Army’s new middle-tier Enduring Shield air defense system, which currently uses the AIM-9X Sidewinder as its interceptor. The service is pushing to acquire a second interceptor option for Enduring Shield, primarily to offer increased capability against faster-flying cruise missiles. Overall, the system is analogous to NASAMS in many ways and would be well-suited to the NCR air defense mission.

The Army currently has two Enduring Shield platoons, one in South Korea and one at Joint Base Lewis-McChord in Washington State. The service is hoping to have a battalion’s worth of the systems by Fiscal Year 2027.

In general, the Army sees Enduring Shield as particularly important to reducing the immense strain on its highly in-demand Patriot surface-to-air missile systems. The service has said that Enduring Shield and Patriot could even be fielded together in composite units in the future. TWZ has been calling attention to the worrisome inadequacy of the Army’s Patriot force to meet current operational needs, let alone the requirements of any future high-end figure, for years now.

If nothing else, Army air defenders protecting the skies over and around Washington, D.C., are set to get an important boost in their ability to spot and track threats, especially cruise missiles and drones, in the coming year.

Contact the author: joe@twz.com