CSIS: US Precision Munitions Stockpile 45–50% Depleted After Seven Weeks of Iran Conflict
A Center for Strategic and International Studies analysis published 22 April 2026 finds that US air-defence interceptors, surface-to-surface ballistic missiles, and cruise missiles have been drawn down by up to half during the Iran war — and that replenishment will take three to five years at current industrial rates.
Technical Summary
A Center for Strategic and International Studies (CSIS) analysis published on 22 April 2026, authored by retired US Marine Corps Colonel Mark Cancian, estimates that US Department of War precision-guided munition (PGM) stockpiles have been depleted by between 45 and 50 percent across multiple critical categories during the first seven weeks of combat operations against Iran. Cancian sets a replenishment timeline of three to five years for most affected systems — an interval that extends beyond the duration of most contemporary conflicts and exceeds the planning horizon of most NATO surge-production models.
Sean Parnell, the Pentagon spokesman, disputed the analysis publicly but declined to release contrary figures. The classified nature of absolute inventory data means CSIS percentages are the clearest open-source indicator available to NATO planners. The 50 percent draw-down figure for endo-atmospheric interceptors is materially higher than the 20 percent draw-down reported for exo-atmospheric interceptors — a distinction that aligns with known engagement-rate differentials between Iranian short-range and longer-range ballistic threats.
Analysis of Effects
The CSIS data covers six precision-munition families. Each performs a distinct tactical role and draws on a distinct production chain.
| Munition | Role | Warhead | Depletion |
|---|---|---|---|
| Precision Strike Missile (PrSM, M1147 Inc 1) | Surface-to-surface SRBM, HIMARS/M270A2 | Unitary HE ~90–100 kg NEQ | ≥45% |
| THAAD interceptor | Exo/terminal phase BMD | Hit-to-kill (no HE) | ≥50% |
| Patriot PAC-3 MSE | Endo-atmospheric air defence | Hit-to-kill + lethality enhancer | ~50% |
| Tomahawk Block V | Sea-launched cruise missile | WDU-36/B ~450 kg NEQ | ~30% |
| JASSM-ER (AGM-158B) | Air-launched stealth cruise | WDU-42/B ~450 kg penetrator | >20% |
| SM-3 / SM-6 | Ship-launched BMD / AAW | SM-3 kinetic; SM-6 HE-FRAG | ~20% |
Hazard-division classification across the suite is mixed. All-up rounds in magazine configuration are typically Hazard Division (HD) 1.1 (mass-detonating). Where rocket motors are separately accessible, solid-propellant grains are typically HD 1.3. The PrSM and Tomahawk families carry the largest unit Net Explosive Quantities (NEQ) in the study — sustained production increases will concentrate demand on insensitive-munition-compliant fills (IMX-101, IMX-104, or PBXN-class compositions) and on the limited pool of qualified filling lines.
Industrial Base and Replenishment Constraints
Cancian states that replenishment will take "one to four years" for most inventories, with expansion beyond current levels requiring "several years after that." Three structural constraints determine whether that timeline is achievable:
- Solid rocket motor (SRM) throughput. PrSM, PAC-3, THAAD, SM-3, and SM-6 all rely on propellant grains cast at a narrow group of US facilities (Northrop Grumman Elkton and Allegany; Aerojet Rocketdyne Camden). SRM capacity, not airframe or seeker, is the binding constraint on interceptor replenishment.
- Energetic-material supply. RDX and HMX production for unitary HE warheads is bottlenecked at Holston Army Ammunition Plant. The October 2025 Accurate Energetic Systems fatality event in McEwen, Tennessee — 16 fatalities, TOSHA-assessed $3.13 million in penalties on 16 April 2026 — remains the contemporary benchmark for industrial risk when energetics production is accelerated without corresponding safety-case reinforcement.
- Qualified workforce. Certified munitions-production technicians, AQAP-2110 quality assessors, and Duty Holder-qualified supervisors cannot be generated on compressed timescales.
Personnel and Safety Considerations
Any accelerated production surge authorised to close the CSIS gap must be reconciled with NATO Allied Ordnance Publication (AOP) safety frameworks, NATO AQAP-2110 quality assurance for munitions, and national ordnance-safety regimes — the UK Defence Safety Authority’s DSA 03.OME and the US Department of Defense Explosives Safety Manual DoD 6055.09-M. An As Low As Reasonably Practicable (ALARP) compliant surge cannot be achieved by relaxing hazard-quantity-distance (HQD) constraints, by increasing personnel limits in explosive workshops, or by raising transient-stock ceilings above safety-case bounds. The Accurate Energetic Systems TOSHA findings cited intentional disregard for net-explosive-weight limits in Building 602 as a proximate cause of the 10 October 2025 fatal event — a direct cautionary signal for current surge planning.
Data Gaps
- DATA GAP: Absolute inventories. CSIS percentages are relative; starting inventories and post-engagement residuals remain classified. Without absolute numbers the depletion rates cannot be reconciled to engagement data.
- DATA GAP: PrSM Increment breakdown. The 45% figure does not separate Increment 1 (unitary HE, land-attack) from Increment 2 (seeker-equipped anti-ship).
- DATA GAP: Warhead-versus-airframe stock. JASSM and Tomahawk warhead inventories may be held separately from airframe inventories, complicating production-restart modelling.
- DATA GAP: Explosive-filling bottlenecks. CSIS does not identify whether the binding constraint is energetic material, propellant, seeker, or final assembly.
- DATA GAP: European alliance stocks. PAC-3 MSE and SM-6 inventories held by NATO partners are not covered in the CSIS figures; the alliance position is therefore opaque.