Is America’s THAAD shield strong enough for a prolonged Iran war? Decoding Pentagon's 'magazine depth'

US President Donald Trump takes a look at a Lockheed Martin THAAD anti-ballistic missile launcher. (AFP File Photo)

• US missile stockpiles face strain amid conflict with Iran
• Interceptor missiles used faster than they can be replaced
• US and Israel face supply constraints as strikes continue

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A rogue nuclear missile is heading to the US. The GBIs or Ground-Based Interceptors have failed and there is no Plan B. This is the plot of 2025 Netflix movie ‘A House of Dynamite.’ But the reel is terrifyingly close to becoming a reality as missiles fly over the Middle East after the US-led strikes killed Iran’s Supreme Leader Ayotallah Khamenei.

With the President Donald Trump admitting that there are likely to be more American casualties in this war, chances of the crisis engulfing the mainland of the US cannot be completely ruled out

Hence, the expanding military campaign against Iran is drawing attention to a critical question: does the US have enough munitions to sustain a prolonged fight while maintaining readiness elsewhere? The Wall Street Journal reported that concerns over interceptor and missile supplies were flagged to President Donald Trump before the strikes began - and those warnings are now being tested in real time. Here’s all you need to know:

Why are US weapons stockpiles suddenly a concern?

The Wall Street Journal said the US military's top general had cautioned Trump that launching a major and extended attack on Iran could strain America's munitions reserves. A key issue was the supply of air-defence interceptors - missiles used to shoot down incoming threats.

As the US works to neutralize Iran's missile and drone forces, it is simultaneously expending interceptors to defend against retaliatory strikes. Officials and analysts told the Journal that these systems can be depleted faster than they can be replenished.

How large is the US interceptor stockpile?

The precise size of the US inventory - referred to by the Pentagon as "magazine depth" - is classified, the Journal noted. However, repeated clashes with Iran and its regional proxies have already consumed significant air-defence resources positioned in the Middle East.

That ongoing drawdown has raised questions about sustainability if the conflict continues.

What is the objective of the current US and Israeli strikes?

Since early Saturday in Tehran, US and allied forces have targeted Iranian missile launchers, drones, airfields and senior leadership sites. A senior official told the Journal that striking first was intended to weaken Iran's ability to mount a large-scale retaliatory barrage.

President Trump said the "heavy and pinpoint bombing" would continue as long as necessary to achieve broader security objectives in the region.

How intense has Iran's retaliation been so far?

Iran's response has been more limited compared with the earlier 12-day conflict, when it fired more than 500 missiles and numerous drones, the Journal reported.

US Central Command said it has successfully intercepted the majority of incoming missiles and drones, though some strikes have landed in Gulf states close to Iran. Analysts caution that further exchanges remain likely.

Are specific US weapons being heavily used?

Yes. Becca Wasser of the Center for a New American Security told the Journal that the Trump administration has fired Tomahawk land-attack missiles (TLAMs) at an extraordinary pace in operations worldwide, including in the Middle East.

These missiles are crucial for infrastructure strikes and would also be in high demand during a potential conflict with China. Wasser noted that in US-China war simulations, TLAMs are often among the first munitions depleted within the opening week, highlighting production challenges.

Is the US using all of its advanced missile systems?

The Journal reported that the current campaign does not appear to rely heavily on long-range US anti-ship missiles - weapons that would be vital in a Pacific conflict. This suggests Washington may be conserving certain capabilities for other contingencies.

What role is Israel playing?

Israel has carried out strikes against Iranian military leadership, helping share the operational burden. However, the Journal reported that Israel also faces supply constraints.

A US official said Israel remains low on Arrow 3 air-defense interceptors and is also short on air-launched ballistic missiles - weapons it has used in previous regional operations.

Could the US tap stockpiles from other regions?

The Journal said the US has already moved substantial missile and interceptor supplies into the Middle East, including assets from partner countries. If the conflict drags on, the Pentagon may need to consider drawing from stockpiles in the Pacific - a move that could carry strategic trade-offs.

What is the broader strategic challenge?

Kelly Grieco of the Stimson Center told the Journal that interceptor systems can be exhausted quickly, warning that "we're using them faster than we can replace them."

The core challenge, analysts suggest, is balancing immediate operational needs in the Middle East with long-term preparedness for other potential conflicts.