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 report highlighted the fact that main obstacle challenging the process of replenishing the depleted weaponry inventories is time, expecting a stage of US vulnerability before the munitions stocks get refilled.
“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,” the report read.
“US 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. It 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.”
“Campaigns 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 report added.
“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.”
“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.”
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, the report added.
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, according to the report.
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.”
“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.”