Mines, missiles and kilometers of coastline: this is what gives Iran the advantage in the Strait of Hormuz

Iran’s threats and attacks on vessels in the Strait of Hormuz have increased the transit risk to the point of halting almost all traffic through this narrow waterway.

The Strait of Hormuz has been effectively closed for nearly four weeks – throwing global oil markets into chaos – and there is no clear end in sight.

Iran’s threats and attacks on ships in the Gulf have increased the risk of passage to the point that almost all traffic has stopped in this narrow maritime corridor, which is the main route for about 20% of the world’s oil and natural gas, as well as fertilizers essential for global agricultural production.

As the energy crisis worsens, US President Donald Trump has highlighted diplomatic efforts to end the blockade, while moving forward with sending thousands of additional troops to the Middle East and weighing the possibility of US Navy escorts for oil tankers.

But Iran continues to have the advantage in many respects — in part because of its unconventional warfare methods, including cheap drones and sea mines, and in part because of its geography. Together, these factors make it more difficult for the United States or other countries to defend vessels or militarily guarantee the security of the strait.

And maintaining control is profitable for Iran. Iranian authorities said they will continue to charge fees for the safe passage of some oil tankers through the strait, after Lloyd’s List Intelligence reported on March 23 that at least two ships paid large sums to cross.

Why does geography favor Iran?

The Strait of Hormuz is about 39 kilometers long at its narrowest, according to maritime analysis firm Vortexa. And virtually all traffic passes through two even narrower main shipping lanes.

“It’s described as a choke point for good reason. There are several choke points in the world, but it could be argued that this one is particularly challenging because there are no alternatives,” said Nick Childs, an expert on naval forces and maritime security at the International Institute for Strategic Studies (IISS).

The Strait of Hormuz is just 24 miles wide at its narrowest point

The Strait of Hormuz is located between Iran and Oman, with their exclusive economic zones in between. The narrowness makes Iranian attacks easier, as ships have little room to maneuver or time to react to threats.

Part of the challenge for vessels and any escort operations is the extreme limitation of maneuver.

“In the open sea there is always the option of diverting course; in a chokepoint this is impossible,” explained Kevin Rowlands, editor of a magazine for the think tank Royal United Services Institute. “That means Iran doesn’t necessarily have to look for its targets. You can just wait.”

In practice, it creates a “kill zone,” he said, where the warning time before an attack can be just seconds.

Furthermore, Iran has around 1,600 kilometers of coastline from which it can launch anti-ship missiles. These batteries are mobile, making them more difficult to eliminate, and the Gulf’s extensive coastline means Iran can strike far beyond the strait itself.

“On the Iranian side, it is not a plain. There are hills, mountains, valleys, urban areas and coastal islands. All of this makes it difficult to detect threats and makes it easier to hide mobile weapons systems,” explained Rowlands, who is also the former director of the United Kingdom’s Royal Navy Center for Strategic Studies, told CNN in an email.

What threats do ships face in the Strait of Hormuz?

Analysts say Iran’s ability to damage commercial vessels through its offensive arsenal has been reduced since the war began.

“However, it is almost impossible to reduce the risk to zero, and we can expect ships to face a residual level of threat for some time from some or all of these systems,” Rowlands said.

Iran has implemented a multi-layered offensive strategy to control the strait.

The Iranian strategy has effectively closed the Strait of Hormuz, and the US is considering naval operations to secure the route. Here are the biggest threats facing civilian vessels in the strait.

The complex threats mean that any operation to escort vessels will likely need to go well beyond a traditional convoy of warships ahead and behind the tankers, according to Rowlands.

“A naval mission is more likely to utilize a layered defense approach, with surveillance from satellites, patrol aircraft and aerial drones. Ships may follow a specific route previously cleared of mines,” he added.

The US has managed to degrade many of Iran’s conventional naval capabilities, Childs said. But the biggest threat continues to come from Iran’s unconventional arsenal, such as drones, small fast attack craft and even unmanned boats loaded with explosives.

“If the Iranians decide to lay mines, they can launch them from a seemingly innocent dhow,” Childs explained. “Although the US has likely accounted for Iran’s main submarines, there are still possibly ‘midget submarines’ to consider,” he added, referring to small submarines that can operate in shallow waters.

US allies, including the United Kingdom, France and Bahrain, are also working on actionable plans to protect international shipping on the route.

What is the current situation?

Iran has attacked at least 19 vessels near the Strait of Hormuz, the Persian Gulf and the Gulf of Oman.

Analysts note that Iran does not even need to destroy the ships to achieve its goal of disrupting global energy trade. As long as the threat remains high enough, shipping companies are unlikely to risk resuming transit. Some vessels linked to Iran, China, India and Pakistan managed to cross the strait.

Iran has stated that “non-hostile vessels” can cross the strait if they coordinate with Iranian authorities. Lloyd’s List Intelligence indicated that at least 16 vessels passed successfully, including one believed to have paid a $2 million fee, as well as several “zombie” tankers that used false identities of dismantled vessels. CNN was unable to independently verify the report.

Even if all tanker traffic resumes, it will take time to clear the congestion: nearly 2,000 vessels are stuck inside the Persian Gulf, according to the International Maritime Organization.

Iran has strong capabilities to attack civilian ships in the Gulf

Iran has attacked at least 19 vessels since the start of the war, according to the Institute for the Study of War. Even so, several ships linked to Iran, China, India and Pakistan will have passed safely.

The Trump administration has been highlighting what it considers to be diplomatic progress. Iran, for its part, claims it is not in negotiations with the US, although it has acknowledged that there has been an exchange of messages through mediators.

Trump’s speech on negotiations comes against the backdrop of thousands of US Marines and sailors heading to the Middle East.

Two US officials told CNN earlier this week that the 11th Marine Expeditionary Unit and the Boxer Amphibious Ready Group are on their way. And US officials previously told CNN that the Marine Expeditionary Unit (MEU) from the assault ship USS Tripoli was being sent to the Middle East, without revealing exactly where it would be deployed or what operations would be carried out.

These MEUs have typically been used for missions such as evacuations and amphibious operations that require ship-to-shore movements, including raids and assaults. That has increased speculation about possible ground operations, although the Trump administration has so far said it has ruled out ground operations in Iran.

Military analysts have indicated that the US may be counting on the fact that just bringing the USS Tripoli and other Marine assets to the region as a threat could be enough to change Iran’s calculations.

Trump also threatens to target more sites linked to the Iranian oil trade if he continues to block the Strait of Hormuz. Last Friday, the US army attacked military facilities on Kharg Island, which handles around 90% of the country’s crude exports. Sites related to the oil trade on the government-controlled island were not hit, but Trump warned they could be the next targets, which would represent further escalation.

CNN’s Brad Lendon, Hanna Ziady, Helen Regan, Haley Britzky and Zachary Cohen contributed to this report