What If the War Lasts Longer Than the Stockpile?
- Wars begin with plans. They do not necessarily end according to them.
The war with Iran has raised an uncomfortable question about American military preparedness. The United States possesses extraordinarily sophisticated missile-defense systems. But even the most advanced interceptor can be fired only if one is available. Interceptors can be consumed in hours or days; replacing them may take months or years.
This is not primarily a question of whether the United States should simply have manufactured more missiles. Nor is it an attempt by an outside observer to second-guess operational decisions made with information that is not publicly available. The more important question concerns an assumption underlying every calculation of military endurance: time.
How long did American decision-makers expect the war to last? And, more importantly, what allowance was made for the possibility that it would last considerably longer?
Military endurance depends not simply on the size of a stockpile, but on the relationship among three variables: the inventory available when hostilities begin, the rate at which weapons are consumed, and the rate at which they can be replaced.
In peacetime, continuing production can create an impression of continuity. Missiles are manufactured, contracts are expanded, and inventories are replenished. In a high-intensity war, however, the arithmetic changes. Consumption can accelerate dramatically while production remains constrained by manufacturing capacity, supply chains, specialized components, and long lead times.
The experience of the 12-day Israel-Iran war in June 2025 had already illustrated the problem. A CSIS analysis of U.S. missile-defense inventories reported that, in addition to Israel’s own use of Arrow and other defenses, the United States employed more than 150 THAAD interceptors and approximately 80 ship-launched SM-3 interceptors during that conflict. CSIS concluded that THAAD expenditure was particularly concerning and emphasized the limits imposed by production capacity and long delivery schedules.
The underlying lesson is simple. A factory continuing to produce interceptors throughout a war does not mean that wartime expenditure is being replenished. If weapons are being consumed much faster than replacements can be delivered, the stockpile is still disappearing.
That is why assumptions about duration matter so much.
An inventory entirely adequate for a campaign lasting several days may become strained if the conflict lasts several weeks. If it continues for months, the same inventory may become a strategic constraint. Ongoing production cannot solve the immediate problem when the time required to manufacture sophisticated weapons is radically different from the time required to expend them.
The difficulty is that the duration of a war is not controlled by one side.
The United States can decide when to attack. It can determine which targets to strike and what forces initially to commit. It cannot determine with comparable certainty how long an adversary will continue fighting, how rapidly that adversary will adapt, or how much ammunition will ultimately be required to defend American forces and allies.
Missile defense makes this asymmetry particularly visible. An adversary does not have to defeat an interceptor technologically to create a strategic problem. It can impose costs simply by forcing the defender repeatedly to use a scarce resource. Every successful interception protects lives and infrastructure, but it also removes an interceptor from an inventory that cannot necessarily be restored during the conflict.
Israel provides a parallel illustration within the same confrontation. Its multilayered missile-defense system is highly sophisticated, yet its endurance in a prolonged Iranian missile campaign is not entirely autonomous. During the June 2025 fighting, the American THAAD and SM-3 interceptors described above were expended largely in defense of Israel, as documented in the same CSIS assessment. The same arithmetic therefore operates on both sides of the alliance: defensive missiles can be expended far more rapidly than they can be manufactured. In Israel’s case there is an additional variable — the continuing availability of American stocks that Washington must also weigh against the requirements of its own forces and other potential theaters.
This makes the adequacy of American inventories more than a logistical question.
More importantly, the danger of a prolonged war does not appear to have been discovered only after hostilities began. On February 23, 2026, before the United States entered the war, The Washington Post reported that Gen. Dan Caine, chairman of the Joint Chiefs of Staff, had warned President Donald Trump and other senior officials that shortfalls in critical munitions would add significant risk to a major military operation against Iran. The report said that U.S. stocks had already been depleted by support for Israel and Ukraine, and that a former defense official had suggested that a major campaign against Iran’s missile program could require strikes on hundreds of targets — a figure that could expand into the thousands, and extend for weeks or months, if the objective broadened.
The concern about duration was reported independently. On the same day, Axios reported that Caine had specifically warned senior officials about the risk of the United States becoming entangled in a prolonged conflict.
The significance of these reports lies not in proving exactly what advice was given behind closed doors; the public cannot know that. It lies in establishing that both the possibility of a prolonged campaign and the pressure on critical inventories were being considered before the decision for war.
The central question is therefore not whether American military planners understood that interceptor inventories were finite. They almost certainly did. Nor is it whether they understood that industrial production could not immediately replace wartime expenditure.
The question is what followed from that knowledge.
If a stockpile is sufficient for a short war but inadequate for a prolonged one, and production cannot close the gap while the war is being fought, then the judgment that the stockpile is sufficient necessarily incorporates an assumption about how long the war will last.
That assumption deserves particular scrutiny, particularly because the conflict subsequently produced the kind of sustained munitions expenditure that the prewar warnings had contemplated.
A CSIS assessment of key U.S. munitions at the ceasefire found that during 39 days of intensive operations the United States had consumed a substantial portion of several critical inventories. The assessment estimated that more than half of the prewar THAAD inventory may have been expended, together with a large share of Patriot interceptors and other precision munitions.
The important point is not that the United States literally ran out of missiles. It did not. The more serious strategic issue is what such expenditure does to the margin available for another contingency.
The same CSIS analysis concluded that, although remaining stocks were still sufficient for plausible scenarios involving Iran, the scale of depletion created a window of vulnerability in the Western Pacific. Rebuilding some of the affected inventories to prewar levels would take years rather than months.
That distinction matters. A stockpile does not have to reach zero before depletion becomes strategically important. Weapons reserved for one theater are unavailable for another, and an interceptor expended in the Middle East cannot simultaneously protect American forces facing a different adversary elsewhere.
None of this establishes that the decision to go to war was wrong. Nor does it prove that defense officials failed to prepare for contingencies that remain classified. There may have been reserves unavailable to public observers, alternative defensive measures, carefully calculated priorities for interceptor use, or strategic considerations that justified accepting the risk.
But it raises a legitimate question about strategic judgment.
If senior decision-makers knew beforehand that a prolonged campaign would place serious pressure on critical inventories, and if those inventories could not be replenished on anything approaching the timescale of wartime consumption, then uncertainty about the duration of the war should itself have been treated as a major strategic variable.
History offers more than enough examples of wars expected to be short that proved otherwise. The reasons vary: an adversary proves more resilient than expected, political objectives change, initial military success fails to produce the anticipated political result, or escalation creates new objectives and new demands. What begins as a limited operation becomes something considerably larger.
The issue therefore extends well beyond Iran.
The United States maintains military commitments across several theaters. Interceptors required in the Middle East are also relevant to the protection of American forces elsewhere and to contingencies involving adversaries with far larger missile arsenals. An interceptor expended today is not automatically replaced tomorrow merely because another has been ordered or is somewhere in a production process.
Industrial capacity is therefore part of strategy, not merely procurement.
Increasing production is an obvious response, and efforts to expand manufacturing capacity are important. But production alone cannot eliminate the underlying problem. No economically realistic stockpile can insure against every conceivable duration and intensity of war. At some point, strategy must confront uncertainty itself.
Before entering a conflict in which critical defensive resources may be consumed far faster than they can be replaced, decision-makers should therefore ask not only whether available inventories are sufficient for the war they expect.
They must also ask whether those inventories are sufficient for the war they might actually get.
This may be one of the more important lessons of the war with Iran. Military superiority is usually discussed in terms of technology, firepower, intelligence, and the ability to strike an adversary. But endurance is also a form of military power.
A strategy that works extraordinarily well for ten days but becomes progressively less sustainable by the thirtieth is not necessarily a bad strategy. Governments sometimes have compelling reasons to accept substantial risks. But the risk should be recognized for what it is.
When weapons can be consumed in days while their replacements require months or years, the decisive assumption may not concern the capability of the weapon at all.
It may simply be the assumption that the war will end in time.