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Imagining an Insurgency in Post-Revolutionary Iran
On 10 September 2026, the Center for Strategic and International Studies, a Washington research institute, published Imagining an Insurgency in Post-Revolutionary Iran. Andrew Faulhaber wrote it as a commentary. He asks what would happen if the United States decided that only a large boots-on-the-ground war, meaning American soldiers physically in Iran, could replace Iran's government, and if the Islamic Revolutionary Guard Corps then fought on as an insurgency. The IRGC is Iran's ideological armed force, separate from the regular army. An American family should care because of the scale he puts on the capital alone. He is illustrating what an occupation would take.
Evidence rating: MODERATE. The rating covers the troop estimate a CSIS visiting fellow published on 10 September 2026: 375,000 to 600,000 counterinsurgents to stabilize Tehran after a regime-change war, drawn from published estimates he links in his text.
What the article says
Faulhaber opens with a question. What if Iran overplays its hand, and the United States decides that regime change through a large ground operation is the only way to restore regional and economic stability? He writes that, beyond the cost of invading Iran, the US military would then likely face a long insurgency led by the IRGC after Iran's regular forces were defeated. An insurgency is a guerrilla war fought after the first battles, to wear an occupier down. He writes that Iran has prepared invasion defenses for decades, and that the IRGC has been arming and training Iranian citizens as young as 12 to fight an invading force. He cites Amnesty International for that age. This page did not open that Amnesty report.
He argues that Iran would try to outlast occupiers: switch quickly from a regular war to an insurgency, trade space for time in mountains and cities, arm supporters, use small attacks, hit outside the main US zones through proxies and the Quds Force, and stretch the war until American politics turn against it. The Quds Force is the IRGC arm that works with allied militias abroad. He also writes that insurgents could potentially turn nuclear material into a dirty bomb, a weapon meant to spread radiation and panic rather than a full nuclear blast. That, too, is his scenario, not a report that one has been built.
On the size of the country, he writes that Iran is nearly one and a half times larger than Afghanistan and Iraq combined, with a population of about 93 million, about 1,500 miles of coastline, and about 15 million people in Tehran. He then gives the figure that matters for an American family.
"Estimates indicate that a force size between 375,000 and 600,000 counterinsurgents would be required to stabilize Tehran."
Andrew Faulhaber, Center for Strategic and International Studies, 10 September 2026. A counterinsurgent here means a soldier whose job is to hold the city and fight guerrillas, not only to win the opening battle. He writes that the high end of that estimate would be 28 percent of the current US military, which he puts at 2.1 million, just to pacify the capital. The numbers 375,000 and 600,000 are links in his text to other published essays. This page did not open those essays.
He compares that range with Iraq. He writes that at the peak of the US occupation of Iraq, the United States had 160,000 counterinsurgents there, about 7 percent of the total force in 2007. He writes that successful stability operations in Tehran alone would likely require at least double those 2007 numbers. He writes that, without a larger force, a counterinsurgency in Iran would probably be split into regions, stabilized one at a time, and that insurgents would want exactly that, because leftover ground would be a refuge.
The italic line under the essay calls him a visiting fellow in the Intelligence, National Security, and Technology Program at CSIS. The author card on the same page says Former Visiting Fellow.
What other reporting and posts add
Another analyst's division math, six months earlier. On 18 March 2026, the economics-and-strategy account Policy Tensor posted a table of Army divisions (a division is roughly 10,000 to 20,000 soldiers) and concluded: "The US cannot occupy Iran even with a draft." It said "You need 4 divisions to occupy Tehran alone," that "Peak global strength with full draft" is 32 divisions, and that even a "super light model" of occupation needs 36, "With the light COIN model you need 60." COIN means counterinsurgency. That is one analyst's arithmetic, not a Pentagon estimate, but it points the same way as Faulhaber's range. @policytensor, 18 March 2026. (capture: twitter/t40__v480.md)
Where the 2026 plans begin. The ground plans reported in 2026 started with raids. The Washington Post reported in March that the Pentagon was preparing for weeks of raids by "a mixture of Special Operations forces and conventional infantry troops" that "would fall short of a full-scale invasion." @Ayei_Eloheichem quoting the Post, 29 March 2026. (capture: twitter/t50__v593.md) Retired Gen. Philip Breedlove was reported noting that the 2003 Iraq invasion "required more than 300,000 US troops," while "the American force now in the region number 50,000, but few are ground troops," as the World Socialist Web Site summarized his Fox interview. WSWS, 16 July 2026. (capture: twitter/t56__v668.md) Faulhaber's 375,000 to 600,000 for Tehran alone is the scale of what a regime-change occupation would add on top of that.
What it shows
A Washington think tank, six months into the war, put the force needed to hold Iran's capital alone at 375,000 to 600,000 troops, up to 28 percent of the entire US military, and at least double the 2007 Iraq peak. The IRGC, he writes, has trained Iranians as young as 12 to fight an invading force.
Numbers like these explain where the road ends. The raids and island seizures the Pentagon planned in 2026 are the first steps; an occupation on this scale cannot be filled with volunteers, which is why the ground-war math leads to the draft machinery described on Reserves, the Guard, and the Road to a Draft. See also Force-Planning Documents and Troop Math.
Check it yourself
No second source was opened for this page. The essays and reports he links, including the pieces behind the 375,000 and 600,000 figures, were not opened.
Status: Andrew Faulhaber is alive. He is the author of a hypothetical. This page does not accuse him of a crime.
Why a think-tank essay belongs here: the United States and Israel began bombing Iran on 28 February 2026, and by September the war had not ended. The Center for Strategic and International Studies (CSIS) is one of Washington's largest defense and foreign-policy think tanks; its analysts brief Congress and the Pentagon. When a CSIS fellow sketches how many American soldiers it would take just to hold Iran's capital, that is a number a family can measure against the size of the whole US military.
Research captures: twitter/t40__v480.md, twitter/t50__v593.md, twitter/t56__v668.md
Last Updated: 2026-09-26