What to know about seven islands forming Iran’s “arch defense”

With thousands of US ground troops reportedly heading to the Middle East, speculation is growing that they could be tasked with seizing Kharg Island—a major fuel hub in the northern Persian Gulf that handles roughly 90% of the country's oil exports. However, Kharg is just one of many Iranian islands in the gulf, and others may play a more decisive role in securing safe passage for ships and naval vessels through the Strait of Hormuz.

Seven of these islands—Abu Musa, Greater Tunb, Lesser Tunb, Hengam Island, Qeshm Island, Larak Island, and Hormuz Island—form what researchers describe as Iran’s “arch defense,” a concept highlighted in a CNN analysis.

“A hypothetical curve connecting these islands would further help to understand Iran’s strategic superiority in controlling the security” of the Hormuz Strait, Iranian researcher Enayatollah Yazdani and Chinese researcher Ma Yanzhe wrote in a 2022 paper for the Canadian Center of Science and Education, as cited by the article.

At the western end of this chain, Abu Musa, Greater Tunb, and Lesser Tunb—despite being the smallest—are especially critical for controlling the strait, the researchers noted.

Because of the relatively short distances between these islands and the shallow waters of much of the gulf, “large warships and tankers are forced to walk past” them. This makes such vessels more vulnerable to attacks from the Islamic Revolutionary Guard Corps (IRGC), including fast-attack boats, naval mines, or drones launched from the islands.

Iranian officials have even described these and other gulf islands as “stationary and unsinkable aircraft carriers,” according to Yazdani and Ma.

CNN reports that the IRGC revealed last year it had strengthened its military presence on Abu Musa, Greater Tunb, and Lesser Tunb.

“Our tactical approach dictates that we must arm and operationalize this group of islands. We have the capability to strike enemy bases, warships, and assets in the region,” said IRGC Navy Commander Alireza Tangsiri at the time.

Because these islands cannot be “sunk,” any Iranian military infrastructure on them would likely need to be neutralized to ensure safe passage for US warships—potentially including those carrying Marine Expeditionary Units—into the heart of the Persian Gulf if an operation against Kharg Island were attempted.

The islands are “strategically located to control any shipping” entering or leaving the gulf, Hawaii-based analyst Carl Schuster, a former director of the US Pacific Command’s Joint Intelligence Center, told the outlet.

According to CNN’s analysis of what a ground operation could look like, deploying forces onto these islands would likely occur either by air or sea.

“The US Navy ships carry landing craft, including LCACs [Landing Craft Air Cushioned] that can slide up onto beaches to disembark troops and their equipment. But getting them inside the gulf could be a problem as their motherships would have to get past possible Iranian defenses on islands earlier in the curve—Hormuz, Larak, Qeshm and Hengam—as well as on the Iranian mainland,” the article notes.

A situation report from the Institute for the Study of War recorded earlier, that US and/or Israeli warplanes had already begun targeting Iranian military infrastructure—including aircraft hangars, ports, and warehouses—on Abu Musa, Greater Tunb, and Lesser Tunb. Such strikes, Schuster noted, would likely precede any amphibious assault.

However, capturing the islands would only be part of the challenge. Maintaining control could require an occupying force of around 1,800 to 2,000 troops to prevent Iran from reusing them, Schuster said.

That scenario could leave US forces exposed to continued threats.

“Controlling any of these territories will also require US forces to prevent drone, missile, and artillery attacks from the Iranian mainland, potentially embroiling the US in a longer-term, unpopular engagement on Iranian territory, accompanied by escalating US casualties,” the New York-based Soufan Center warns, as cited by CNN.

By Nazrin Sadigova