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The 2026 Estimates: What Washington's Analysts Said a Ground War Would Take
Once the bombing began on 28 February 2026, the old question came back with new urgency, and the same institutions that sized an Iran ground war in 2007 and 2009 sized it again. Their answers fall on a ladder: tens of thousands to hold the Hormuz coast, half a million to secure the country after a collapse, 375,000 to 600,000 to hold Tehran alone. And Congress's own research service told lawmakers in September that "ground forces" and occupying "some portions of Iran's territory" were a live branch of the war.
Evidence rating: CONFIRMED for each quoted estimate, from the named publication.
The ladder
| Rung | Estimate | Who | Source |
|---|---|---|---|
| Hold 50–100 miles of the Hormuz coast | "low tens of thousands of U.S. troops in Iran" | Michael O'Hanlon, Brookings | podcast, 21 May 2026 |
| Secure Iran after the regime falls | "well over half a million troops, at least initially" | Kenneth Pollack, Foreign Affairs | 18 Mar 2026 |
| Stabilize Tehran alone | 375,000 to 600,000 | Andrew Faulhaber, CSIS | 10 Sep 2026 |
| Full invasion | 300,000 to 500,000, as an estimate passed on by | Gaurav Selopal, MP-IDSA (India) | 2 Apr 2026 |
O'Hanlon: "several American brigades plus the support ashore"
On a Brookings podcast on 21 May 2026, asked how big an operation to reopen the Strait of Hormuz would be, O'Hanlon said holding 50 to 100 miles of coast, and protecting the troops, means tens of thousands of soldiers, since a brigade typically holds about a 25-kilometer front:
"But I think you're gonna have to have several American brigades plus the support ashore, which means low tens of thousands of U.S. troops in Iran."
He said the operation was doable, with a risk of hundreds or more American casualties and of thousands of troops bogged down in Iran for a long time. His colleague Robert Kagan said Iran's control of the strait had reversed the balance of power (a196). In March, O'Hanlon had asked Congress to "Authorize Limited Airstrikes but Rule Out Ground Forces," noting that such a bar "would not preclude a large raid on Iran's nuclear facilities by U.S. Special Forces" (Foreign Affairs, 30 Mar 2026).
Pollack: "well over half a million"
Kenneth Pollack, former CIA Persian Gulf analyst and lead author of the 2009 Brookings study (see Which Path to Persia), wrote that it has proved impossible to remove a regime without some kind of ground force, and that a collapse would leave a security vacuum unless a large force stepped in at once. Securing Iran is "an operation that would require well over half a million troops, at least initially." He wrote that the United States was "not interested" in that job (a197).
One day later, Israeli Prime Minister Netanyahu said "you can't do revolutions from the air" and "there has to be a ground component, as well," without saying whose. See Israeli leaders on a ground war.
Faulhaber: 375,000 to 600,000 for Tehran
Andrew Faulhaber of CSIS imagined a US decision that only a large ground war could replace Iran's government, followed by a Revolutionary Guard insurgency. Iran, he wrote, is nearly one and a half times the size of Afghanistan and Iraq combined, with about 93 million people and 15 million in Tehran.
"Estimates indicate that a force size between 375,000 and 600,000 counterinsurgents would be required to stabilize Tehran."
The high end, he wrote, is 28 percent of the current US military, which he put at 2.1 million, for the capital alone. At the peak of the Iraq occupation the United States had 160,000 there (a195).
The Congressional Research Service: ground forces are a branch of this war
The Congressional Research Service (CRS), the nonpartisan research office of the Library of Congress, updated its report "U.S. Conflict with Iran" (R48887) on 18 September 2026. Listing how the war could widen, it wrote that outcomes would depend on
"whether the United States introduced ground forces or attempted to displace and occupy some portions of Iran's territory."
It named Iran's enriched uranium stockpile, Kharg Island, and the coast along the Strait of Hormuz as possible targets of a wider campaign, and warned that Iranian forces might be better able to hit closer targets such as US ground forces inside Iran (CRS R48887; a205). That is Congress's own reference material treating American ground troops in Iran as a live possibility.
An outside view: MP-IDSA, India
The Manohar Parrikar Institute for Defence Studies and Analyses, funded by India's Ministry of Defence, concluded on 2 April 2026: "Analyses agree that boots on the ground would be necessary only if objectives expanded to regime change or seizure of nuclear facilities" (a224). Both triggers then came up: Netanyahu called for a "ground component" for regime change and said of the uranium, "You go in, and you take it out." CNN reported in June that the US military rushed to prepare a ground mission for the uranium before it was paused. See Kharg Island and the uranium raid.
What the ladder shows
Each rung is bigger than the forces sent. About 5,000 Marines and a brigade of paratroopers went to the region in March. The smallest rung, holding the coast, is "low tens of thousands" in Iran. The rungs above it are the size of the entire active Army or more. A war that starts on the bottom rung has nowhere to get the soldiers for the next one without a mobilization. See troop math and Reserves, the Guard, and the road to a draft.
Related Areas
Status: Michael O'Hanlon is alive. Robert Kagan is alive. Kenneth Pollack is alive. Andrew Faulhaber is alive. Gaurav Selopal is alive. Benjamin Netanyahu is alive.
Last Updated: 2026-09-26