When Iranian Foreign Minister Abbas Araghchi said Tehran had spent two decades studying US wars to build a system that could keep fighting even if the capital was bombed, he was describing more than resilience; he was outlining the logic of Iran’s defence doctrine.

At the centre of that doctrine is what Iranian military thinkers call “decentralised mosaic defence” – a concept built on one core assumption: that in any war with the United States or Israel, Iran may lose senior commanders, key facilities, communications networks and even centralised control, but must still be able to keep fighting.

That means the priority is not simply defending Tehran, or even protecting the supreme leadership itself. It is preserving decision-making, keeping combat units operational and preventing the war from ending with a single devastating strike.

In that sense, Iran’s military was not built for a short war. It was built for a long one.

What is mosaic defence?

“Mosaic defence” is an Iranian military concept most closely associated with the Islamic Revolutionary Guard Corps (IRGC), particularly under former commander Mohammad Ali Jafari, who led the force from 2007 to 2019.

The idea is to organise the state’s defensive structure into multiple regional and semi-independent layers instead of concentrating power in a single command chain that could be paralysed by a decapitation strike.

Under this model, the IRGC, the Basij, regular army units, missile forces, naval assets and local command structures form parts of a distributed system. If one part is hit, others keep functioning. If senior leaders are killed, the chain does not collapse. If communications are severed, local units still retain the authority and capacity to act.

Advertisement

The doctrine has two central aims: to make Iran’s command system difficult to dismantle by force, and to make the battlefield itself harder to resolve quickly by turning Iran into a layered arena of regular defence, irregular warfare, local mobilisation and long-term attrition.

That is why Iranian military thinking does not treat war primarily as a contest of firepower. It treats it as a test of endurance.

Why did Iran adopt this model?

Iran’s shift towards this model was shaped by the regional shocks that followed the US invasion of Afghanistan in 2001 and Iraq in 2003.

The rapid collapse of Saddam Hussein’s regime appears to have left a deep mark on Iranian strategic thinking. Tehran saw what a highly centralised state looked like when confronted with overwhelming American military power: The command structure was struck, the system fragmented and the regime fell quickly.

Rather than making its military more dependent on central control, it moved towards diffusion. Rather than assuming it could match US or Israeli conventional superiority, it focused on surviving it.

Iran’s doctrine assumes that any invading or attacking force will have far superior conventional technology, air power and intelligence capabilities. The answer, in Iranian thinking, is not symmetrical confrontation. It is to disrupt the enemy’s advantages, prolong the conflict and raise the cost of continuing it.

How would it work in war?

In practice, the doctrine assigns different roles to different institutions.

The regular army, or Artesh, is expected to absorb the first blow. Its armoured, mechanised and infantry formations serve as the initial line of defence, tasked with slowing enemy advances and stabilising the front.

Air defence units, using concealment, deception and dispersal, try to blunt enemy air superiority as much as possible.

The IRGC and the Basij then take on a deeper role in the next stage of conflict. Their task is to turn the war into one of attrition through decentralised operations, ambushes, local resistance, disruption of supply lines and flexible operations across varied terrain, including urban centres, mountains and remote regions.

This is where the Basij becomes especially important. Originally founded by order of Ayatollah Ruhollah Khomeini, the force was later more tightly integrated into the IRGC’s wartime structure. After 2007, its units were folded into a provincial command system spanning Iran’s 31 provinces, giving local commanders wider room to act according to geography and battlefield conditions.

Advertisement

That local autonomy is central to the doctrine. It means war can continue from below even if leadership from above is degraded.

Beyond the land battle, naval forces play their part through anti-access tactics in the Gulf and around the Strait of Hormuz. Their mission is to make free movement dangerous and costly through fast attack craft, mines, antiship missiles and the threat of disruption in one of the world’s most sensitive energy corridors.

Missile forces, especially those controlled by the IRGC, serve as both deterrent and deep-strike capability, aimed at imposing costs on enemy infrastructure and military targets.

Then comes Iran’s wider regional network: allied armed groups and partner forces across the Middle East, whose role is to widen the battlefield and ensure that any war with Iran does not remain confined to Iranian territory.

Instead of allowing the enemy to isolate one front and destroy one command structure, Iran seeks to spread the war across time, geography and multiple layers of conflict.

Why time matters

One of the clearest expressions of this doctrine is economic as much as military.

A Shahed drone, for example, is widely estimated to cost tens of thousands of dollars to manufacture. Intercepting it can cost vastly more once interceptor missiles and integrated defence systems are taken into account.

That asymmetry matters because it turns time into a strategic weapon.

If one side can produce low-cost weapons in large quantities while forcing its opponent to spend far more to defend against them, then prolonging the war itself becomes a means of pressure. The point is not necessarily to win through immediate battlefield superiority. It is to make the cost of stopping every threat unsustainable over time.

That is one reason Iranian military doctrine places such emphasis on endurance, stockpiles, decentralisation and attrition. It is built around the possibility that the stronger side may eventually find the price of continued escalation too high.

The influence of prolonged war theory

Iran’s doctrine did not emerge in an intellectual vacuum. It overlaps in important ways with the theory of prolonged war most famously associated with Mao Zedong.

During the Japanese invasion of China, Mao argued that a weaker side did not need to defeat a stronger enemy quickly. It could instead survive the initial imbalance, stretch the conflict, wear down the enemy’s logistics and political will, and gradually alter the balance over time.

Iran’s doctrine is not a copy of Mao’s model. But it shares the same central premise: that war is not decided only by relative military capability at the outset. It is also shaped by time, endurance, adaptability and the ability to survive the opening shock.

That logic influenced many 20th-century conflicts, from Vietnam to Algeria to Afghanistan. It remains central to how analysts understand the staying power of weaker states and armed groups facing militarily superior enemies.

Advertisement

Who developed this thinking inside Iran?

Among the most prominent ideological figures associated with this thinking is Hassan Abbasi, a hardline strategist often described as one of the IRGC’s key theorists of asymmetric and long-duration conflict.

Abbasi’s importance lies not only in military ideas but also in the way he connects strategic concepts to ideological narrative. In Iran’s system, prolonged war is not treated purely as an operational necessity. It is also framed as a political and civilisational struggle in which society, belief and state institutions must all be prepared to absorb pressure and keep functioning.

That makes the doctrine broader than battlefield planning. It becomes a way of organising state resilience.

Mohammad Ali Jafari, meanwhile, helped translate much of this thinking into institutional form. Under his leadership, concepts such as decentralised defence, localised command, irregular response and distributed resilience became more deeply embedded in the IRGC structure.

What is the “fourth successor”?

Perhaps the clearest expression of this wartime logic lies in succession planning.

Before his killing, Supreme Leader Ali Khamenei reportedly instructed senior Iranian officials to ensure that multiple predesignated successors existed for every key military and civilian post. The reported number was as many as four replacements for each senior position. That is what gives rise to the idea of the “fourth successor”.

The point was not merely to name an heir at the top. It was to build layers of succession throughout the system so that the assassination, disappearance or isolation of one leader would not create paralysis. Even if a first replacement could not assume control, a second, third or fourth would already be in line.

At the same time, a narrow inner circle was reportedly authorised to take key decisions if communication with the top leadership became impossible.

This reflects the same logic as mosaic defence: Do not allow the system to depend on any single node. Make it possible for the state to keep operating even after severe shock.

Why does this matter now?

Because the doctrine suggests Iran was preparing for exactly the kind of war its adversaries hoped would break it quickly.

The United States and Israel have long relied on doctrines of rapid dominance, precision targeting and leadership decapitation. In that framework, destroying command centres, communications nodes and senior figures is expected to produce systemic collapse, or at least strategic paralysis.

Iran’s answer has been to design against that outcome. This does not make the system invulnerable. It does mean it was built on the assumption of severe loss and disruption, with continuity preserved through redundancy, decentralisation and organisational resilience.

That approach was shaped not only by foreign threats, but also by Iran’s own internal history. In the years after the 1979 revolution, the new regime faced violent challenges from armed opposition groups, most notably the Mujahedin-e Khalq, whose assassinations and bombings exposed the fragility of a leadership-centred order.

The Iran-Iraq War reinforced the same lesson. Eight years of attritional conflict gave the Islamic Republic experience not only in mobilisation and endurance, but in governing through prolonged war.

A doctrine built to survive shock

Taken together, all of these point to a simple conclusion: Iran’s strategy was not designed for a brief exchange of blows.

It was designed for a war in which commanders might be killed, communications severed, infrastructure hit and central authority strained – but in which the state, the armed forces and the wider security system would continue functioning.

Advertisement

That is the significance of mosaic defence. It is not simply a military tactic; it is a theory of survival.

It assumes that the enemy may dominate the skies, strike first and strike hard. But it also assumes that war can still be extended, dispersed and made costly enough to frustrate the search for quick victory.

That is where the “fourth successor” puzzle fits in. It offers a window into a broader Iranian view of conflict: that the system must be able to absorb shock, replace itself under fire and turn the passage of time into part of its defence.

By that measure, the death of a leader – even one as central as Khamenei – was never meant to mark the end of the fight. It was something the doctrine was built to outlive.