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Blocking the Strait of Hormuz

April 20, 2012

At least 20% of the world’s oil supply transits through the Strait of Hormuz which is, on average, around 30 miles wide.

Strait of Hormuz

Strait of Hormuz Shipping Lanes


The Wall Street Journal recently had an analysis of the military challenges in what would be an asymmetrical war, with big ships challenged by swarms of speedboats carrying anti-ship cruise missiles. This is similar to China’s current strategy for access denial in the South China Sea.

The WSJ article mentioned that Iran had over 5,000 mines, but the number is of only secondary importance.

Iran’s ability to lay a few hundred bottom mines in the Strait is crucial to any analysis, and this wasn’t discussed in any detail in the WSJ article.

A cursory look at the map shows that Qeshm, an island about two-thirds the length of Long island in New York, and larak island, are bordering the entire northern flank of the strait, while the eastern flank is bordered by Iran proper.

Not shown on this map, but a serious consideration, is that mountains 10,000 feet high rise abruptly from the Iranian shoreline. Qeshm Island is relatively flat, with cliffs and heights at the western end.

Iran’s strategic position is important since clearing bottom mines is a lengthy process involving surface ships and helicopters that will be exposed to fire from Qeshm and Larak islands and the eastern Iranian shore.

Mine warfare detachments, helicopters and ships are stationed in Bahrain, with Oman also being a probable base of operations. Most mines will be between 150 and 300 feet under water, with mud and other objects making it difficult to locate their exact positions.

The mine clearing operation consists of discovering where the mines are located using scanning arrays towed by helicopters or ships, and then using unmanned underwater vessels (UUVs) to attach explosives to the mines to destroy them.

The UUVs are controlled from the surface, either with helicopters or ships.

It will be necessary to completely neutralize Qeshm and Larak islands and the eastern shore of Iran in order to protect the mine clearing helicopters and ships. Most likely, Qeshm and Larak will need to be occupied.

Under the best of conditions, it will require months, not days, to clear a few hundred bottom mines from the strait. No official estimates have been made public, but it could easily require four to six months to clear the bottom mines from the strait.

Our strategic petroleum reserve (SPR) has been established to provide oil in the event the Strait is closed.  The SPR is designed to help offset a loss of our normal imports, but due to physical limitations, only about 5 mbd can be pumped from the SPR. This, coupled with domestic production and reduced imports, can supply our needs at high cost for about four months, but then there would be shortages.

It’s highly likely that price controls and/or gasoline rationing will be instituted when world oil prices head toward $200 per barrel or the SPR is emptied.

Obviously, the more oil we can produce in North America, the less need there will be for rationing or price controls.

Exactly how oil prices and supplies will react is conjecture, but worth taking into consideration.

It is a simple matter for Iran to lay a few hundred bottom mines across the Strait of Hormuz.

Here is one such fictional scenario occurring before hostilities actually begin.

In eight minutes, heading north from Bandar Abbas, the planes had passed over Qeshm Island and were over the Strait.

They flew side by side with three miles separating each plane. In this formation they cut a swath 20 miles wide as they headed for the shipping lanes.

Each C-130 was equipped with rails on each side of the plane’s cargo floor leading to the rear ramp and door. Mines were placed vertically on dollies that rolled along the rails with 10 mines on each side of the plane. When the rear door was opened, the mines could be rolled out the C-130. As the mines were released from the plane, a cord attached to the plane would pull out the arming plug so the mines were armed as they left the plane.

Each bottom mine weighed 2,000 pounds, and the load of 20 mines were well within the carrying capacity of each C-130 aircraft.

The crews of these planes practiced for the past three months over the interior of Iran. Using dummy mines, they had flown about one hundred feet over the ground and had become proficient at releasing the mines at one- to two-minute intervals. Flying at slightly over 100 knots, they would lay a mine every two to three miles.

Now they headed over the Strait of Hormuz to perform the mission for which they had trained.

When the lead, left most plane in the formation was five miles from the shore of Qeshm, they started to lay their mines. As each mine fell from a plane, a small drogue chute opened to help slow the mine so as to minimize any damage that might occur as the mine entered the water.

In 35 minutes, all 200 mines were laid in the Strait of Hormuz and shipping was completely blocked.

A swarm of small boats could also lay bottom mines that sit on the ocean floor waiting for a ship to pass overhead.

Blocking the Strait of Hormuz by Iran would be an act of desperation and national suicide, but whether Iran’s government is rational, in the Western sense, is a question mark.

While Iran would ultimately fail, it will take more time than many contemplate to open the Strait to shipping – and it only makes sense for us to expand our oil production to minimize the effect of any such disruption in oil supplies.

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2 Comments leave one →
  1. kakatoa permalink
    April 20, 2012 10:42 am


    Yes, it would likely be a major mess if Iran’s political leaders felt it necessary to block the straight to save their power. As almost none of the oil the US consumes these days come from their lets hope that our friends in Europe, Russia and China would be willing to pick up some of costs associated with cleaning the mess up.

    I found EM’s post on the subject of the closure to be an interesting read.

  2. April 20, 2012 11:04 am

    I hadn’t seen the referenced article, but it is very good. It covers more information than I did, since I try to keep my articles short.
    His discussion of different mine types is good, and shows there are several types that would fit the bill in terms of blocking the strait.
    Bottom line: Iran can easily block the Strait and it will be hard for us to clear the mines. It will take months, not days to open the Strait, and will probably require invading some areas to keep shore installations from attacking our mine clearing operations.
    There is also the danger of Shia uprisings in the Eastern Province which is where Saudi Aramco produces its oil. This and other asymmetrical warfare items are very possible in a war with Iran.
    One more thought:
    China has been a leader in developing mine warfare capabilities, while our Navy has been very slow to modernize its mine warfare capabilities.
    My article next Tuesday will deal with another aspect of this issue.

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