What is the Strait of Hormuz? Can Iran shut off access to oil?


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What is the Strait of Hormuz and why are people worried about it?

Iran has been threatening to shut down the Strait of Hormuz, a choke point between the Persian Gulf and the Arabian Sea. The waterway is bordered to the north by Iran, and its closure could cut off access to 20% of oil shipped around the world, sending fuel prices skyrocketing.


Why is Iran threatening to close it?

Iran has been under increasing pressure to stop its nuclear program. The European Union just approved an embargo on Iranian oil Monday to punish the country. Iran insists it is only working on nuclear power and medical research, but Western countries believe it is trying to create a nuclear weapon.

To counter that pressure, Iran has played up its power over the strait. A Revolutionary Guard commander was quoted in a Tehran newspaper saying government leaders would not ‘allow a drop of oil’ to pass through the strait if ‘our enemies block the export of our oil.’

MAP: Strait of Hormuz

Putting it even more boldly, ‘closing the Strait of Hormuz for Iran’s armed forces is really easy ... or, as Iranians say, it will be easier than drinking a glass of water,’ Iran’s top naval commander said on television in December. The country has also been test-firing missiles to show control of the strait.

Why is this waterway vulnerable?


There are a few things that make the strait vulnerable. Its narrowest point is only 34 miles wide. Oil tankers can only use one channel to come in and one channel to come out, each of them roughly two miles wide. Iran has claimed sovereignty over a few islands near the western entrance to the strait.

How would Iran close the strait?

Nobody is worried that Iran would actually put a barrier in front of the Strait of Hormuz. ‘What most people think of -- and what the Iranians would probably do -- is a combination of things that would not really close the Hormuz Strait but make traversing it very difficult and risky so that people would not go through,’ said Afshon Ostovar, a senior analyst at the nonprofit research organization CNA.

Iran could do that by using everything from mines to submarines to missiles to small boats that harass ships. Political scientist Caitlin Talmadge outlines one scenario: Iran could set mines in and around the shipping channels, then attack from the air or the coast when people try to clear them.

INTERACTIVE: The world’s oil

But Talmadge points out that the bluster from Iran makes any attempt to plant lots of mines without being detected “essentially impossible.”


Could Iran really shut down the strait?

Many experts are skeptical that Iran could or would carry out the threat. In a recent article for Foreign Policy Magazine, Ostovar dubbed it a “kamikaze act” because Iran would be devastated by an all-out war with the United States, which could be triggered by closing the strait.

Defense Secretary Leon E. Panetta called it a “red line” that would spur the U.S. to react. Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, says Iran could block traffic “for a period of time,” but that the United States could reopen it the strait. U.S. officials have said it could be done within a week.

Closing the strait would also hurt Iran. Most Iranian imports and exports come and go by sea, a report from the Institute of Near East and Gulf Military Analysis points out. And Ostovar adds that stopping traffic in the strait would also harm Asian countries that aren’t among Iran’s enemies, such as India and China.

However, a new report suggests that the Iranian threat could become more real in a decade or two. The U.S. has historically relied upon its allies in the Persian Gulf region to provide bases from which it can deploy troops and get supplies. Iran is now building weapon systems that could to stop that, possibly by threatening governments that offer bases to the U.S. military.

Deploying lots of ground forces and bombers ‘worked for Operation Desert Storm and for Operation Iraqi Freedom,’ said Mark Gunzinger, co-author of the report from the Center for Strategic and Budgetary Assessments.’We need to think through -- what if we’re not able to do that?’


If closing the strait is an extreme or unlikely step, what else could Iran do?

Iran has a wide range of other ways to use its power in the gulf, from seizing ships to raiding facilities offshore. It can also use small ships to damage or detain tankers or board merchant ships to slow down shipping, harassment that falls short of war. Those minor attacks could reduce traffic or raise insurance costs for shippers. And those attacks don’t need to be at or near the Strait of Hormuz.

“Everyone uses ‘close the gulf’ as sort of a slogan,” said Anthony Cordesman, a strategy expert with the Center for Strategic and International Studies. “But Iran has demonstrated that it would look at a whole range of different ways to put pressure on the Arab Gulf states and the West.

“It wouldn’t make any sense at all for Iran to concentrate all of its assets around one narrow point and make it extremely easy to attack them,” he added.


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-- Emily Alpert