The Missile Defense Agency (MDA) is suffering from a gap between procurement and delivery of new Terminal High Altitude Area Defense (THAAD) missile defense interceptors, with missiles bought in 2021 not slated to show up in the agency’s inventory until April 2027, experts warned. “There is a projected gap between July 2023 and April 2027 of deliveries for THAAD interceptors for the United States,” said Wes Rumbaugh, a fellow at the Center for Strategic and International Studies (CSIS) Missile Defense project, in an online presentation of his recent study on the issue on Wednesday. The CSIS analysis, “The Depleting Missile Defense Interceptor Inventory” released on Dec. 5, examined not only the THAAD interceptor inventory, but also stockpiles of the Army’s Patriot PAC-3 Missile Segment Enhanced, and the Navy’s Standard Missiles-3 and -6. “You know, it used to be that they said you couldn’t hit a bullet with a bullet. Now we’re doing it so frequently, we’re afraid we don’t have enough of them,” said Tom Karako, head of the CSIS Missile Defense Project.

While exact THAAD and other missile defense numbers are classified, the CSIS study analyzed procurement data from the Defense Department comptroller and found that MDA now has a backlog of 100 THAAD missiles — missiles procured between fiscal 2021 and 2024 but not yet delivered. “As of the June 2025 budget release, this gap is not slated to end until April 2027 when MDA will receive interceptors that it obligated procurement funds for in FY 2021,” the study says. In response to Breaking Defense’s request for comment, MDA forwarded the request to the Office of the Secretary of Defense, which did not respond by press time. While the study stressed that estimating the number of missile defense interceptors of any type in Pentagon inventories is “is trickier than it might first appear” due to how budgetary data is reported and the gaps between procurement and delivery, Rumbaugh said Wednesday that he assessed the number of available THAADs in the inventory to be 534 — at least prior to June, when the US Army fired an unknown number of interceptors in Israel to help blunt Iran’s missile and drone barrage.

“The United States has fielded eight THAAD batteries, each with six launchers and eight interceptors per launcher, or 48 interceptors per battery. Under this assumption, that would mean that 384 of the previously delivered THAAD interceptors were assigned to fielded THAAD launchers, which would leave 150 for reload and spare capacity,” according to the CSIS study. That number, however, is likely quite a bit lower now, after the Army was reported to have over the summer fired anywhere from 100 to 250 interceptors from THAAD batteries in defense of Israel. Rumbaugh said today it’s unclear exactly how many, but reported ranges provide an idea. “If two batteries were deployed, they would be able to fire 96 interceptors before needing to reload. This would line up with the most optimistic estimates of THAAD use of about 100 interceptors,” the report explained. “If the reported number of 150 interceptors used is correct, that would mean using about 54 additional interceptors from the reload stockpile, about a third of the inventory previously unassigned to a launcher. That would also leave only 96 interceptors to restock the two batteries, which would leave the force without any reserve interceptors,” it added.

Restocking THAAD

CSIS stressed that while DoD has “taken some steps” to restore the THAAD inventory, doing so is more challenging than one might think. The first problem that “continued budgetary uncertainty will hinder execution and longer-term solutions,” the study said. For example, the study found that the Pentagon in May and June “reprogrammed over $700 million into the FY 2025 THAAD procurement program from previously approved Israel Security Supplemental Act funds” — or enough to cover 45 missiles at $15 million apiece. In FY26, MDA asked for 25 interceptors in its base budget request, and 12 more from the reconciliation bill, the study added, noting that there remains uncertainty about the fate of the latter request as negotiations with Congress over DoD’s freedom to program reconciliation funds continue. In any event, CSIS asserted that although “this funding provides a start, it still falls short of replacing even the most optimistic assessments of THAAD expenditures.”

The second problem in the Pentagon’s effort to replenish THAAD stockpiles is the inability of the industrial base to ramp up production due to inconsistent financial demand from the US government, CSIS explained. This isn’t because production lines at prime manufacturer Lockheed Martin have gone cold; on the contrary the company in January announced it had delivered the 900th THAAD to date MDA. “The question is, because the production line isn’t cold — the industry is making announcements about delivering additional THAAD interceptors. And so our assumption is that they’re working on something like an FMS [foreign military sales] case,” Rumbaugh said. (A Lockheed spokesperson deferred a request for comment to MDA.) The Pentagon could always insist its orders go to the front of the line, but the study warned against pulling rank. “Simply prioritizing U.S. interceptors and pushing those procurements to the front of the production line risks undercutting future international sales by creating uncertainty about previously agreed delivery schedules,” the study cautioned. “[T]he more often the U.S. jumps the production line, the likelier it is that allies and partners will search for alternative suppliers.”

A Way Ahead

Rumbaugh said that his analysis suggests DoD needs do a couple of key things to stabilize missile defense interceptor acquisition, production and ultimately inventory levels not just for THAAD, but for all of its air and missile defense interceptor types. First, it needs to address budgetary uncertainty and swings in procurement orders from year to year due to the fact that so much funding comes from supplemental monies. While often supplemental funds have been significant, the process doesn’t actually help to convince industry that continued funding is stable enough for them to invest in more capacity. Second, to overcome the problem of long lead times, Rumbaugh’s study suggested that DoD “could codify additional munitions requirements, including the need for larger stockpiles of replacement interceptors, through the Munitions Requirement Process,” Importantly, the study said, any new requirements for THAAD and other interceptors should take into account the “high deployment rate” and include both a steady stockpile to meet “the pacing challenge” as well as additional ones for contingencies.

“You got to build the ramp and build a stable ramp for industry to want to walk up that thing,” he said. Otherwise, CSIS warned bluntly, the US military will face the same problem of having to scramble to replace depleted munitions across the. missile defense sector over and over. “If every use of a U.S. air and missile defense interceptor is going to produce another round of discourse about inventories, then it is time to reevaluate either the deployments themselves or how to procure enough interceptors to avoid handwringing,” the study concluded.