How Successful Has Iran’s Passive Defense Doctrine Been?

Following the air campaign launched against Iran by the United States and Israel on 28 February 2026, the passive defense infrastructure Tehran has been building for more than two decades was subjected to a comprehensive test for the first time. On one hand Iran’s deep underground facilities withstood powerful American conventional weapons; on the other, the capacity sheltered in those facilities became steadily less accessible. In short, although passive defense proved more effective than expected, on its own it could not provide an adequate security umbrella.

What is the passive defense doctrine?

The passive defense doctrine is the product of two traumatic experiences that left deep marks on Iran’s strategic memory. The first of these is the Iran-Iraq War. Between 1980 and 1988 Iraqi Scud attacks targeted Tehran directly, and the use of chemical weapons resulted in the death or injury of more than 100,000 Iranians. That war showed Iran’s leadership two fundamental realities: the resilience of infrastructure is an essential part of national resistance capacity, and a state subjected to international arms embargoes must establish its security largely with its own means.

The real turning point came in 2003. With the invasion of Iraq, American forces were deployed on Iran’s eastern and western borders. Supreme Leader Ali Khamenei defined passive defense as an existential necessity and in October 2003 had the National Passive Defense Organization (Sazman-e Padafand-e Gheyr-e Amel) established within the General Staff of the Armed Forces. Brigadier General Gholamreza Jalali of the Islamic Revolutionary Guard Corps (IRGC), who had a background in architecture and engineering, was appointed to head it. Jalali held the post for more than twenty years. The organization developed in three phases:

The first phase (2003-2009): military fortification and underground construction activity came to the fore in this period.

The second phase: under President Mahmoud Ahmadinejad, the concept of passive defense merged with the doctrine of economic resistance. As sanctions turned into a kind of “economic war,” passive defense also acquired an economic dimension.

The third phase: beginning with the Stuxnet attack of 2010, the scope of passive defense widened in this phase, and cyber defense, information control and countering soft war were brought within the framework. Accordingly, a Cyber Defense Headquarters was established within the organization in 2011.

Missile cities

The most visible investment of passive defense is the underground missile complexes, or, in the words of former IRGC Aerospace Force commander Hajizadeh, the “missile cities.” IRGC officials have claimed that there are hundreds of underground bases in the Zagros and Alborz ranges, some reaching depths of 500 metres. Since the first underground base was built in 1984 the network has expanded, and under a 1993 agreement with North Korea some 18 ballistic missile shelters were constructed.

These tunnels are fitted with automated rail transport systems, compartmentalized chambers, blast-resistant doors and side tunnels that channel shock waves. In 2018 the IRGC announced that missile factories had also been moved underground. In March 2025 — only weeks before the war — state media presented to the press the “largest underground missile city,” containing Ghadr-H, Emad, Kheibar Shekan, Sejjil and Haj Qassem ballistic missiles.

In the nuclear field the best-known case is Fordow. Built near Qom at a depth of 80 to 90 metres inside hard limestone and dolomite formed under tectonic pressure, the facility began as an IRGC missile base before being converted into a uranium enrichment plant.

Alongside hardened infrastructure, Iran has also invested in mobile missile systems and deception measures. It is assessed that before the war its inventory held some 300 to 400 mobile launchers (TELs). Some missiles, such as the Kheibar Shekan, were deployed concealed inside civilian truck chassis. Decoy launchers producing radar returns and thermal signatures were also developed. By contrast, before the war there were serious shortcomings in functional bomb shelters in Tehran and other major cities.

The function of the passive defense doctrine in the war

At the end of the war’s first month, the dimensions in which passive defense proved effective should not be overlooked. Foremost among them is the resilience the deepest underground missile cities showed against the most powerful American conventional weapons. According to a satellite imagery analysis reported in the press examining 107 tunnels at 27 underground bases, although 77 percent of the entrances were struck, the inventory inside was largely preserved. This constitutes a historical data point showing the limits of conventional air power. Despite the GBU-57, the largest conventional bomb in the world, the granite barriers of the Zagros weakened the effect of the attack.

Second, as the first month of the war has passed, Iran is seen to be still able to use its ballistic missile capacity. Of a pre-war inventory holding 2,500 to 3,000 ballistic missiles and 300 to 400 TELs, an estimated third remains usable. A scenario in which Iran was wholly disarmed has not materialized. This shows that its deterrent capacity has not been eliminated entirely.

Third, the most important success in strategic terms has been the dispersal of nuclear material. It is claimed that Iran’s stockpile of roughly 400 kilograms of uranium enriched to 60 percent was moved to different locations before the strikes, under a dispersal operation planned in advance. The Director General of the International Atomic Energy Agency (IAEA), Rafael Grossi, has stated that somewhat more than 200 kilograms of this stockpile remains underground at Isfahan, while the whereabouts of the rest are unknown. If these claims are accurate, this element of passive defense could, by the end of the war, become one of Iran’s strongest cards at the negotiating table alongside the Strait of Hormuz.

Fourth, Iran has been able to shift to its “mosaic defense” doctrine despite the collapse of central command. Although the killing of Khamenei and the loss of more than 40 senior officials was a major blow, Iran was able to move to a decentralized command structure. This shows that the flexibility envisaged by the passive defense doctrine has functioned to a degree. Whether it has been fully successful is debatable, but it is clear that a total collapse of the system was prevented.

Fifth, the deception measures have shown invaluable cost-effectiveness. In several instances Israel’s and the United States’ expensive precision munitions were spent on emplaced decoys. This pattern, which began with the October 2024 strike, has continued in the present war. Satellite imagery has confirmed that some of the “launchers” struck were in fact decoys. This is an asymmetric success.

Yet the paradox emerges at precisely this point. The inventory of 2,500 to 3,000 ballistic missiles and 300 to 400 TELs held before the war appears to have fallen over time to roughly 1,000 missiles and 100 to 150 usable launchers. Israel has claimed that more than 300 launchers were destroyed, of which 95 were said to have been buried under rubble when tunnel entrances collapsed. The fundamental issue is this: the concealment achieved over years disappears at the moment of use. Every launch exposes the launcher’s position to an enemy with air superiority, continuous drone surveillance and strike capacity. Accordingly, the daily ballistic missile launch rate fell by 86 percent in the first two weeks. For the basic assumption of passive defense is that it operates beneath an active air defense umbrella. That umbrella collapsed within hours.

The United States, for its part, adapted tactically in theatre. Unable to penetrate facilities at a depth of 500 metres, its strategy shifted to entrance denial and area denial. Accordingly, tunnel entrances were collapsed, ventilation shafts were neutralized, and on 26 March it was reported that anti-tank mines were scattered at the exits of missile bases.

At Fordow, the first combat use of the GBU-57 in June 2025 produced results by a method the passive defense engineers had not foreseen. Instead of penetrating by brute force, structural weak points were targeted. Twelve MOPs were guided through two ventilation shafts in a “double tap” method. The desired effect was achieved through overpressure and blast wave propagating along the open tunnels. The bomb’s void-sensing smart fuse increased effectiveness by delaying detonation when it detected an air pocket during penetration. The IAEA confirmed that almost all the sensitive equipment at Fordow was destroyed. The absence of adequate blast compartments in the long tunnels allowed a single successful penetration to spread through the entire facility.

The most conspicuous structural gap in passive defense lies in the field of civilian resilience. The organization’s remit covered energy, health, industry and food supply chains, but the greater part of twenty years of investment was allocated to military assets and civilian infrastructure was neglected. There are no functional bomb shelters in Tehran and the major cities. More critical still is food and water security. Iran’s food supply chain is still standing and functioning. But grain imports, which run through Iran’s southern ports, have come to a halt with the effective closure of Hormuz. In a country that before the war had silo infrastructure with a capacity of many tons, operational stocks are assessed to have fallen dramatically. Strikes on energy infrastructure have also created an indirect food crisis. Israel’s strike on the South Pars gas field on 18 March threatened a resource supplying 90 percent of Iran’s energy and directly affected both domestic consumption and fertilizer production. Passive defense protected the missiles, but the capacity to feed the population is at risk.

What does the picture tell us?

Although passive defense is an intelligent investment for a middle-sized power facing a technologically superior adversary, the 2026 war has revealed three realities:

First, passive defense is a mechanism that complements active air defense rather than one that substitutes for it. When the protective umbrella collapses, all the capacity beneath it is exposed. Iran’s S-300 batteries had already been eroded in earlier Israeli strikes, while the indigenous Bavar-373 system had never been tested under high-intensity combat conditions. Both systems proved inadequate against the combination of F-22, F-35 and EA-18G.

Second, the fundamental paradox of underground storage is that what is protected must at some stage be brought to the surface in order to be used. Combined with continuous drone surveillance and precision strike capacity, that moment produces a lethal bottleneck. The strategy of entrance denial and area denial has systematically turned that bottleneck into a devastating vulnerability.

Third, and perhaps most important, the most decisive passive defense success in strategic terms was also the lowest-cost element: the dispersal of enriched uranium to different locations before the bombardment began. If these claims are accurate, this element will be one of Iran’s strongest cards at the negotiating table apart from the Strait of Hormuz.

In sum, Iran’s Passive Defense Organization can be assessed as one of the most ambitious conventional survival programmes a middle-sized power could develop in the face of technological superiority. Twenty years of underground construction produced facilities capable of resisting even the most powerful conventional weapons. Yet passive defense cannot fully protect the Islamic Republic from the consequences of a devastating military offensive.

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This article was first published in IRAM on April 1, 2026.