Rebuilding U.S. Missile Inventory: A Multiyear Project

Source: CSIS

The 39-day bombing and air defense campaign against Iran depleted inventories of key U.S. munitions stockpiles, as a previous CSIS analysis detailed. The United States has enough munitions for any plausible scenario in the Iran war, but the depleted inventories have created a window of vulnerability for a potential Western Pacific conflict. The time needed to rebuild those inventories has thus become a major concern.

Defense Secretary Pete Hegseth stated that it will take “months and years . . . depending on the weapon system” to replenish U.S. inventories. CSIS analysis supports the secretary’s assessment. Table 1 shows replacement times for seven key munitions heavily used during the Iran War that would also be needed for a Western Pacific war. Under the current delivery projections:

• Land Attack Missile (TLAM), Terminal High Altitude Area Defense (THAAD), and Patriot—heavily used in this war—will take three or more years from today to return to prewar inventory levels.
• Standard Missiles (SM-3 and SM-6) will take around two years. These naval missiles were not used as heavily.
• Joint Air-to-Surface Standoff Missile (JASSM) and Precision Strike Missile (PrSM) will take several months to a year to replace. The prewar PrSM inventory was low because the system had just begun production. JASSM, though heavily used, will see large deliveries from recent procurements.

Table 1: Key Munition Stockpiles and Timelines to Rebuild

	Estimated use in Iran War	FY 2027 request	Deliveries in FY 2026	Annual production capacity (Current maximum rate / framework agreement goal)	Estimated return to prewar inventory
SM-3	130–250	214	52	156 / 250	Early 2029
Patriot	1,060–1,430	3,203	172	2,000 / 2,000	Mid-2029
SM-6	190–370	540	125	239 / 500	Late 2028–early 2029
Tomahawk	1,000+	785	207	600 / 1,000	Late 2030–early 2031
PrSM	40–70	1,134	70	680 / 550	Late 2026
JASSM	1,100+	821	484	860	Mid-2027
THAAD	190–290	857	92	96 / 400	Mid to late 2029

Note: Current maximum production rate represents the surge capacity achievable with existing facilities. The Trump administration has signed multiyear framework agreements with industry that, in most cases, expand production capacity beyond the current surge level. Production capacity does not equate to actual production rate because budgets may not fund production to capacity. No new capacity target has been announced for JASSMs. SM-3 target capacity is estimated based on FY 2027 budget materials as press releases on the framework agreement do not specify a quantity. This table combines variants of a given missile system—SM-3 Blocks IB and IIA are reported together; so are PrSM Baseline and Increment 2.

Source: Authors’ calculations based on FY 2027 and past Department of Defense (DOD) budget materials. The technical note at the end of this commentary details the methodology for estimating delivery timelines. Estimated expenditures and inventories are discussed in Mark F. Cancian and Chris H. Park, “Last Rounds? Status of Key Munitions at Iran War Ceasefire,” CSIS, May 28, 2026.

ampaigns against Iran and its proxies—and, for Patriot interceptors, aid to Ukraine—have made the problem more acute. Alongside replenishing its own stocks, the United States also has to fulfill orders from allies and partners. Decisions on how to allocate new production have already created bilateral friction, and this friction will continue for the next few years as demand outpaces supply.

The Trump administration understands the urgency. Large munitions procurement in the president’s $1.5 trillion FY 2027 defense budget reflects these magazine depth concerns. A war supplemental for additional munitions funds is expected as the DOD seeks to replace what was expended in Operation Epic Fury and then build inventories above the prewar levels. The administration has also signed a series of framework agreements with industry to expand munitions production capacity, which could expedite future deliveries.

The figures in this article illustrate the deliveries of the seven key munitions to U.S. stockpiles in the coming years.

• The red bars show cumulative additions to U.S. inventories each quarter, according to the latest budget justification books. The bright red bars indicate when the FY 2027 orders are projected to arrive. The slow deliveries for most munitions stem from the relatively low level of funding in prior years.
• The gray bars indicate current inventory levels, with shaded areas representing the delta between low and high estimates.
• The green line shows the maximum potential rate of inventory growth. It assumes that (1) industry achieves capacity goal targets set in the framework agreements, (2) industry then produces at that level, and (3) all deliveries go to U.S. inventories rather than to those of allies. It illustrates how the delivery schedule could improve as production capacity increases.
• The black line represents missile inventories before the 2026 Iran War. Where the black line crosses the stacked bars is when missile deliveries equal prewar inventories.

Many Years to Replace

Tomahawk

Tomahawk procurement averaged 86 missiles in the past 10 fiscal years (FY 15–FY 26), with most orders coming from the Navy. While Raytheon’s goal is to have the capacity to make more than 1,000 Tomahawks per year, the recent annual production rate is less than 200 because of small past orders. Existing orders will begin replacing the 1,000+ Tomahawks expended during the Iran War, but will not be enough to fully restore inventories to prewar levels.

The Navy requested 785 Tomahawks in the FY 2027 budget—a huge increase from prior years. Based on current DOD delivery projections, these missiles will start arriving in U.S. inventories in March 2030, after 34 months of production lead time. U.S. inventory will replace TLAMs fired against Iran by late 2030.

Figure 1: Tomahawk, U.S. Inventory

Note: “Deliveries (past procurement)” includes TLAMs procured in FY 2022 onward. Missiles procured in prior years have already been delivered.

Source: Authors’ calculations based on FY 2027 DOD budget materials.

Allied orders also need to be fulfilled. The 400 missiles due to Japan reportedly may be delayed as the DOD prioritizes refilling U.S. stockpiles, even as a Japanese destroyer recently completed the requisite modifications. Australia also purchased more than 200, and the Netherlands, 175.

THAAD

The large procurement request in the FY 2027 budget reflects the urgency of rebuilding the THAAD inventory after high operational use in Operations Epic Fury and Midnight Hammer.

Previous years’ budget documents projected zero deliveries to the United States between August 2023 and April 2027, after which missiles purchased in FY 2021 would begin to arrive. Updated schedules in the FY 2027 materials show earlier orders already being delivered, with FY 2025 procurement scheduled for delivery throughout 2026. To cope with the near-term shortfall, deliveries were apparently re-sequenced to prioritize U.S. needs over those of allies and partners.

The Army has requested 857 THAAD interceptors in FY 2027. Their deliveries, projected to start in mid-2029, will complete the replacement of Iran War usage by the end of calendar year 2029.

Figure 2: THAAD, U.S. Inventory

Note: Because THAAD deliveries have been re-sequenced, the prewar inventory estimate is revised to 452, up from 360 in the “Last Rounds?” analysis. “Deliveries (past procurement)” includes THAAD interceptors procured in FY 2025 onwards. Missiles procured in prior years have already been delivered.

Source: Authors’ calculations based on FY 2027 DOD budget materials.

The delivery timelines in the budget documents imply that THAAD production is at the current surge rate of 96 interceptors a year. With additional facilities and tooling, Lockheed Martin plans to expand production capacity to 400 a year, a needed increase to fulfill large U.S. procurement orders and those of allies. The allied backlog includes a Saudi order of 360 interceptors in 2017, which has been partially fulfilled, and a 2022 Emirati purchase of 96 missiles. Additional orders can be expected because Saudi Arabia and the United Arab Emirates expended a large portion of their inventories defending themselves against Iranian missiles in the initial campaign.

Patriot

Patriot deliveries pose a dilemma for the United States because of the need to replenish its own inventories, help Ukraine defend against Russian missile attacks, and meet the needs of 17 other countries that use the interceptor. Current production of the latest variant—PAC-3 Missile Segment Enhancement (MSE)—is around the baseline rate of 650 interceptors per year, with half the deliveries going to the United States and the rest to allies and partners. The surge annual production rate with existing tooling and facilities is 2,000. Lockheed intends to scale up to this level.

Because U.S. procurement in the last decade has averaged 225 missiles per year, deliveries from prior years will not be enough to fully replace expenditures. For that, the United States will need to wait for the 3,203 Patriot missiles requested in the Army’s FY 2027 budget. These are projected to start delivery in May 2029.

Figure 3: Patriot, U.S. Inventory

Note: “Deliveries (past procurement)” includes Patriot interceptors procured in FY 2023 onwards. Missiles procured in prior years have already been delivered.

Source: Authors’ calculations based on FY 2027 DOD budget materials.

The United States continues to send Ukraine Patriot missiles, among other weapons and munitions. Missiles contracted under the Ukraine Security Assistance Initiative during the Biden administration are beingdelivered to Ukraine as they are manufactured. The Prioritized Ukraine Requirements List (PURL), a new mechanism under which NATO states pay for weapons in U.S. inventories, has provided a near-term bump in Patriot deliveries to Ukraine. Both delivery mechanisms may be affected by the Trump administration’s efforts to prioritize U.S. needs with future deliveries to Ukraine being pushed back in the queue.

Other allies also await Patriot deliveries. Since 2020, U.S. allies and partners have purchased nearly 1,900 MSE interceptors and more than 700 of earlier variants such as the PAC-2 and Guidance Enhanced Missile-Tactical (GEM-T).

Table 2: PAC-3 MSE, Major Arms Sales Notifications Since 2020

Country	Interceptors Purchased
Denmark	20
Germany	600
Kuwait	84
Netherlands	34
Qatar	300
Saudi Arabia	730
Spain	51
Switzerland	72
Total	1891

Source: Defense Security Cooperation Agency, U.S. Department of State.

Several Years to Replace

SM-3 and SM-6

Ship-launched interceptors, SM-3 and SM-6, have seen less use than ground-launch systems. A CNN report citing DOD sources indicated that actual Standard Missile usage in Operation Epic Fury was closer to the lower-bound estimates in the CSIS munitions inventory study. This lower use reflects the more distant location of U.S. naval assets—out in the Arabian Sea and Eastern Mediterranean—and the short range of Iranian fire, with the bulk of it against Gulf States. No warship capable of firing these air defense interceptors operated inside the Persian Gulf before the ceasefire.

Figure 4: SM-3, U.S. Inventory

Note: Includes SM-3 Block IB and IIA. The United States resumed procurement of Block IB missiles after initially suspending. “Deliveries (past procurement)” includes Block IB procured in FY 2024 onward and Block IIA procured in FY 2020 onward. Missiles procured in prior years have already been delivered.

Source: Authors’ calculations based on FY 2027 DOD budget materials.

Figure 5: SM-6, U.S. Inventory

Note: “Deliveries (past procurement)” includes SM-6s procured in FY 2023 onward. Missiles procured in prior years have already been delivered.

Source: Authors’ calculations based on FY 2027 DOD budget materials.

Both missiles have lengthy production lead times. The Missile Defense Agency and the Navy requested large quantities in the FY 2027 budget: 78 SM-3 Block IBs, 136 SM-3 Block IIAs, and 540 SM-6s. These orders will take between 36 and 39 months to begin deliveries once Congress provides appropriations. Because of the small size of past orders, inventories will not return to prewar levels until early 2029 despite the relatively low usage in the campaign.

Months to Replace

JASSM

U.S. forces began this campaign with a sizable JASSM inventory. The Air Force has procured large quantities of these long-range cruise missiles since the 2000s—on average, nearly 500 a year for the past decade. To deliver these orders, current production appears to be already at the surge rate unlike the other munitions discussed in this article. Further, the missile was not used in operations until 2018. Thus, while over 1,100 JASSMs were expended, U.S. inventories will recover fairly quickly as past orders are delivered.

Figure 6: JASSM, U.S. Inventory

Note: Figures include both JASSM-Extended Range (ER) and Extreme Range (XR) variants. ER procurement ended in FY 2025; XR procurement began in FY 2024. “Deliveries (past procurement)” includes JASSMs procured in FY 2023 onward. Missiles procured in prior years have already been delivered.

Source: Authors’ calculations based on FY 2027 DOD budget materials.

In the past five years, U.S. allies have ordered nearly 1,200 JASSMs, including 821 missiles by Poland and 120 by the Netherlands.

Precision Strike Missile

The PrSM inventory was small at the beginning of this campaign because the Army received approval for full production and deployment only last July. Accordingly, use has been limited—though highly effective—and replacing expenditures will take only a few months.

Figure 7: PrSM, U.S. Inventory

Note: “Deliveries (past procurement)” includes PrSMs procured in FY 2023 onward. Missiles procured in prior years have already been delivered.

Source: Authors’ calculations based on FY 2027 DOD budget materials.

The large procurement orders in the last few years—and the anticipated FY 2027 buy—keep production at the projected surge capacity. All deliveries will go to the U.S. inventory for now. While the baseline PrSM has been approved for export to Australia and the United Kingdom, no foreign sales announcement has yet been made.

On Estimating Munitions Deliveries: Technical Note

Munitions inventories are classified, and some delivery timelines are unavailable. Sufficient public information exists, however, to make estimates with requisite fidelity to inform the policy debate.

CSIS estimates on when procured missiles enter U.S. inventories relied primarily on two data points: rate of production and procurement lead time. The DOD provides three different rates of production in its annual budget materials:

• Minimum Sustaining Rate (MSR): The rate required to maintain a continuous production process.
• Economical Production Rate (“1-8-5”): one eight-hour shift each per day, five days a week.
• Maximum Production Rate (“Max”): surge capacity using multiple shifts with “extant or prior year tooling.”

Even if existing facilities are used, achieving surge capacity is expensive and time consuming as it requires hiring additional personnel and resolving supply chain bottlenecks. The production schedule in DOD’s P-21 budget exhibits provides a sense of where current production rates fall between the MSR and the surge rate for individual systems. Reporting inconsistencies across weapon systems complicate the analysis. The justification books also generally omit delivery timelines for missiles procured through reconciliation. This adds further uncertainty to assessing FY 2027 procurements since the bulk of missile funding is in the reconciliation request. Where data was unavailable, delivery schedules were estimated using the latest procurement lead times, cross-referenced against production capacity limits.

The framework agreements between the Trump administration and industry have set ambitious production capacity goals that could significantly increase deliveries over the next five to seven years as new facilities come online. Capacity, however, does not equate to actual production. To illustrate the potential production increase, the “maximum potential inventory, with framework surge” curve in this analysis—depicted in green—is modeled as an annual linear increase from current capacity to stated industry goals.

Procurement lead time refers to the number of months needed between Congress appropriating the funds and missile delivery. As Figure 8 shows, this time can be divided into three pieces:

• Administrative Lead Time: This measures the time between appropriation and a signed contract. After Congress appropriates funds, it takes several months for the DOD to negotiate and sign a contract with defense companies. Multiyear procurement seeks to reduce this time.
• Production Lead Time: This measures the time between contract award and first delivery. Lead time lengthens when demand outpaces a contractor’s capability or when deliveries to allies and partners are sequenced between U.S. deliveries.
• Full Lot Production Time: A given year’s procurement is delivered over several months. This measures the time between the first delivery and the last delivery, typically less than 12 months.

As an example, the JASSMs procured in the FY 2027 budget are forecasted to be put on contract six months into the fiscal year (administrative lead time). The first missile in this lot is expected to be delivered 36 months after the contract is signed (production lead time). It will take another 11 months until all missiles are delivered (lot production).

Figure 8: Forecasted Procurement Lead Time

Months

Note: Timelines in this figure are the latest DOD projections and can fluctuate based on industry capacity and allied orders. The figure includes only the administrative lead time forecasted to be needed after funds become available. Some administrative actions take place earlier, as they do not require funding.

Source: Authors’ calculations based on FY 2027 DOD budget materials.

The Future of Munitions Inventories

Funding for additional munitions began in the Biden administration and has accelerated under the Trump administration. Congress has supported this funding reflecting bipartisan agreement on the issue. As a result, the problem today isn’t money; it’s time. It takes time to expand production capacity and to build these complex systems.

Thus, there will be a window of vulnerability for several years until inventories return to their previous levels and another several years before they get to the levels that war planners desire. The DOD will need to make plans for dealing with this gap. Some munitions could be substituted, but these carry tradeoffs. Alternative ground attack munitions, for example, are short- or medium-range and increase vulnerability of the launch platforms. Alternative counter-drone systems are expensive.

The situation in the Western Pacific is not all bleak, however. The world has seen the great skill of U.S. military forces not just in the conflict with Iran but in operations against Venezuela and the Houthis. China is deeply aware that it has no recent combat experience and that it performed poorly in its last war—against Vietnam in 1979. That difference in experience may preserve deterrence until munitions inventories are restored.

Our Defense and Security Department colleagues Seamus Daniels and Wes Rumbaugh provided helpful comments to an earlier version of this article. We also thank Hunter Macdonald and Sabina Hung for the expeditious review and formatting.

This Commentary was written in support of a project funded by the Smith Richardson Foundation.

Mark F. Cancian (Colonel, U.S. Marine Corps Reserve, ret.) is a senior adviser with the Defense and Security Department at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Chris H. Park is a research associate for the Arleigh A. Burke Chair in Strategy at CSIS.