On March 1, 2026, two days after American and Israeli strikes killed Ayatollah Ali Khamenei and dozens of senior officials, Iranian Foreign Minister Abbas Araghchi posted a message that read less like grief and more like a warning. “We’ve had two decades to study defeats of the US military to our immediate east and west,” he wrote on X. “We’ve incorporated lessons accordingly. Bombings in our capital have no impact on” Iran’s ability to fight. He was describing a doctrine that most Western planners had heard of but few had taken literally — one now being tested in real time as the war enters its eleventh day.
That doctrine is called “decentralized mosaic defense,” and it was built for exactly this moment: a war in which Iran’s supreme leader is dead, its communications are degraded, its capital is under sustained bombardment, and its military is still firing missiles at US bases and Gulf states.
Designed to Lose the Head and Keep the Body
The Islamic Revolutionary Guard Corps (IRGC) announced the model of mosaic defense in 2005 under the supervision of General Mohammad Ali Jafari — who led the Guards from 2007 to 2019. Farzin Nadimi, a defense specialist at the Washington Institute, explained that “it is designed to help the local provincial IRGC and their accompanying Basij elements to defend against an outside invading force”. Under this doctrine, the IRGC has been reorganized into 31 autonomous units — one dedicated to Tehran and the other 30 for the remaining provinces.
The logic is simple. Mosaic defense is often explained with a basic idea: “decapitation is not a silver bullet“. The goal is to keep the “body” functioning even if the “head” is struck — by building overlapping chains of command and dispersed stockpiles. Every unit effectively has a full “military” at its disposal, with its own intelligence capabilities, weapons stockpile, and command-and-control. In the provinces of the Zagros Mountains, each unit specializes in using narrow passes and cave systems. The mosaic doctrine envisions the terrain itself becoming a communication obstacle for the enemy, while local units know every path.
The doctrine was forged from trauma. Araghchi said Iran had “two decades to study defeats of the US military to our immediate east and west”. In both cases, US “shock and awe” tactics led to military control — but establishing lasting political stability in the face of decentralized insurgencies proved impossible, and the US ultimately withdrew from both theaters. Iran drew the opposite lesson from Saddam Hussein’s fall in 2003: highly centralized militaries collapse quickly once their leadership is removed.
The Fourth Successor
The deepest expression of this thinking lies in succession planning. Sources close to the late Khamenei revealed that he had outlined a four-layered succession plan for each key military and governmental role, with each position having up to four designated replacements. The concept — known internally as the “fourth successor” — was designed to ensure that no single assassination could paralyze the system. Deputy Defense Minister Reza Talaeinik stated that every position in the military chain of command has named successors “stretching three ranks down” who are ready to take over immediately.
On February 28, 2026, Ali Khamenei was assassinated in a series of airstrikes conducted by Israel and the United States. Trump boasted that “the attack was so successful it knocked out most of the candidates. It’s not going to be anybody that we were thinking of because they are all dead”. He told Fox News that 48 senior Iranian leaders were killed in the bombings.
Yet within ten days, the Assembly of Experts had convened and named a successor. Mojtaba Khamenei was named Iran’s new supreme leader, succeeding his father just more than a week after he was killed. A statement from the Assembly of Experts said Mojtaba had been selected as the third leader of the Islamic Republic. The killing of his parents, wife, and son in US-Israeli strikes made him a symbolic figurehead for pro-regime supporters and sent a firm message about the inviolability of Iran’s sovereignty.
The Doctrine’s Weakness Is Its Strength
Western analysts are divided on whether mosaic defense is genuine resilience or organized chaos. Colin Clarke, executive director of the Soufan Center, noted that “decentralized military units will be more difficult to find and finish off, but they will also be less impactful because they won’t achieve critical mass”. He added that “some of the more disciplined and elite units will be able to stay in the fight, while other, less experienced units will fall victim to confusion and disorder”.
The Strait of Hormuz offers a case study. Araghchi attributed strikes against Oman to “a mistake by autonomous units who could not be directly reached” — a statement that could reflect genuine command fragmentation or deliberate deniability. Either way, maritime chokepoints could become more unpredictable if provincial naval or missile units operate with expanded tactical authority, and even limited disruption in the narrow corridor could jolt global oil markets.
The economic asymmetry reinforces the doctrine’s logic. A Shahed drone costs tens of thousands of dollars to build; intercepting one can cost over a million. Iran relies on irregular tactics to drag out the war, primarily through economic coercion and cost asymmetry. As long as Iran can produce low-cost weapons and force its adversaries to spend vastly more defending against them, time itself becomes a weapon.
The CFR warned before the war that the most likely outcomes for leadership change in Iran are also the least auspicious for US interests — a new supreme leader drawn from Khamenei’s orbit or a shift to military leadership would likely extend the theocracy’s most destabilizing policies. That prediction has arrived. Iran’s military was not built for a short war. Eleven days in, it is being tested on those terms — and the doctrine’s designers would say that is exactly the point.
Original analysis inspired by Shady Ibrahim from Al Jazeera. Additional research and verification conducted through multiple sources.
By ThinkTanksMonitor
