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Assessing the Iranian Threat to the Strait of Hormuz

Original Article By: Caitlin Talmadge
International Security Fall 2008 vol 33 no 1
Major Topic: Politics
Minor Topic: Security


         By preventing oil transport through the Strait of Hormuz, Iran could keep one quarter of the world's oil production from reaching the market. A full closure or even the threat of conflict would cause a massive price and supply shock.

         The author seeks to answer six questions:

         1) Does Iran have the capability to close the Strait of Hormuz?

         2) What could cause Iran to act?

         3) What are Iran's capabilities for fighting in the Strait of Hormuz?

         4) What is a likely campaign scenario?

         5) What can the U.S. do to counter Iran?

         6) What would be the costs and the outcome for the U.S.?

         Concerning these questions, analysts are all over the place. The author, however, believes that Iran cannot truly block the strait. Further that if it tries, the U.S. reaction would eventually secure the strait but the U.S. would not defeat Iran quickly.

         Iran can disrupt shipping with mines, missiles, aircraft and smaller boats. It could, therefore, take weeks possibly months for the U.S. to clear the strait.

         Mine clearing would result in a greatly increased chance of escalation as the U.S. would seek to eliminate threats against its mine counter-measures (MCM) ships. These threats include anti-ship missiles, their targeting radar, the Iranian air force and navy. In any conflict Iran has certain geographical advantages such as several islands in the strait, a long coastline with many naval bases, air-defense and missile sites and a dozen ports.

         Iran is unlikely to want to firmly close the Strait because its own oil is shipped through the Strait of Hormuz. However, Iran may try to close the strait if its nuclear instillations were attacked, if it suffered a nuclear attack, if it is on the verge of collapse or defeat in an invasion.

         The author believes that the best hope Iran has for a limited victory involves creating a trap for U.S. forces where it can bring all its assets to bare. Initially Iran would mine the strait. Then the U.S.'s mission would be to clear those mines; whereupon Iran's goal would be to interfere and raise the costs to the U.S.

         Iran has three weapon types that would interfere with the American efforts: mines, anti-ship missiles and air-defenses.

         In the case of mines, the key question is: how many mines could Iran lay before being detected and forced to stop?

         Iran has many platforms that could be used to lay mines including hundreds of ships, several submarines and scores of helicopters. The author seems to think that Iran has about 2000 mines.

         Various calculations have concluded that it would take about 2000 to 3000 mines to close the Strait of Hormuz. Although Iran has the lower limit, The power of mines to affect behavior comes from the fear they create rather than a true risk analysis. Therefore even if Iran did not succeed in laying all its mines, shipping and insurance companies may be more risk averse and stop or limit shipments in a partially mined strait.

         The author's calculations suggest that Iran could, at most, lay 693 mines before being forced to stop by a U.S. intervention. This intervention would likely be a part of Iran's overall strategy.

         The American's first mine clearance task would be to create a Q-route. The author defines a Q-route as: “an initial passage through a minefield in which the chance of hitting a mine is believed to be reduced to 10 percent or less and through which essential traffic can flow, including the MCM vessels themselves.” therefore a Q-route would need to clear about 70 mines.

         The author considers several mine clearing operations to estimate the length of time needed to clear a minefield. These include the British at Gallipoli (1915), The U.N. At Wonsan (1950), operation Earnest Will (1987), operation Candid Hammer (1991) and the effort to clear the Khor Abd Allah water way during operation Iraqi Freedom (2003).

         Considering the data from operation Candid Hammer and the estimate of 693 mines, the author believes it would take 3.9 days to clear a Q-route and 31.2 days to clear 80% of the mines.

         Considering the data from operation Iraqi Freedom the slightly improved estimate is: 3.6 days to clean a Q-route, 28.4 days to clear 80% and 35.5 days to clear all the mines.

         Bear in mind that clearing speed is affected by the type of mine, the quality of the MCM assets, climate and geography. Additionally, in a conflict in the Strait of Hormuz the U.S. would not possess 6 advantages it enjoyed in the operations Candid Hammer and Iraqi Freedom. The advantages were 1) mine clearing is easier in smaller areas, however, the Strait of Hormuz is larger than the areas of the earlier operations. 2) Iran has access to more sophisticated mines than the Iraqis, thereby making clearance more time consuming. 3) In the past the U.S. had massive allied support and MCM assets readily available – this may not be true in the strait. 4) The U.S. is in the process of phasing out its dedicated MCM assets in favor of a more multi-role force. 5) The dedicated MCM teams spent a lot of time updating hydrographic maps thereby making it easier to identify possible mines. It is unclear whether this mission will be positively or negatively affected by the phase out. 6) Most importantly, the two base cases occurred in permissive and un-hostile environments which cannot be assumed in a conflict in the Strait of Hormuz.

         In short these estimates are best case scenarios and therefor give a likely lower limit to the time required to clear the minefield.

         Iran could try to attack MCM ships in the strait in two ways: 1) Small boat suicide missions like the attack on the USS Cole in 2000, but the U.S. has learned lessons from that incident and attacks of this kind are unlikely to succeed again. 2) Anti-ship missiles – these are believed to be the primary threat.

         Iran is believed to possess several hundred anti-ship cruise missiles and dozens of batteries. It is believed that these missiles can be launched from ships, aircraft and trucks.

         There are two categories in which anti-ship missiles fall: Line-of-sight targeting (LOS) and over-the-horizon targeting (OTH). The author believes that it is possible but unlikely that Iran has any OTH anti-ship missiles.

         LOS targeting missiles are easier to spot and kill. Israel showed in 2006 against Hesbollah that wiping out all coastal radar would result in each missile battery having to use its own radar system to target. This would result in its easy detection, targeting and destruction. Iran would have to trade one missile battery for every attempt to kill a ship.

         Iran is unlikely to have OTH targeting missiles due to the problem of “clobber” over long distances. The author defines the “clobber” problem as “terrain elevations that would obstruct the flight path of the low-flying missile.” (page 103) The problem is overcome by advanced hardware processing large amounts of detailed topographical data with sophisticated software which Iran apparently lacks.

         The author identifies about 16500 square kilometers of Iranian territory that is suitable for LOS missile staging areas.

         To defend, the U.S.'s first priority would be to destroy Iran's radar stations. Since radar calls attention to itself, this should be an easy task. The second priority would be to detect missile launches. American satellites, AWACS planes, Aegis warships, Global Hawks and Predator vehicles can triangulate data and determine an exact locations in minutes. It would take 5 aircraft continuously circling in patrol over the 16500 square kilometers to kill any missile launch vehicles within a maximum of five minutes of the missile launch. With 4 aircraft needed to maintain each patrol, one Nimitz class carrier should be enough. The length of this operation would depend on Iran and its launching schedule.

         Once a missile is launched, its chances of hitting a ship are small. The Aegis weapon and radar system provides extremely robust and effective missile defense.

         Iran's air force is old, decrepit and ill trained. By a wide consensus, it is no match for a modern air force. In contrast, Iran's air defenses are well funded and well maned. But there are weakness. The number of batteries is small when compared to the size of the country. In other words they are thinly spread. Furthermore Iran, long under economic sanctions, has, from a variety of nations, a variety of systems which do not always work well together. Iran's air defenses are unimpressive but still threatening. The U.S. will need to use air defense suppression assets to counter this threat.

         The author looks at the U.S. operation in Kosovo to see how the U.S. might handle the threat and concludes that since U.S. air defense suppression assets are scarce the actual number of sortie will be less than the maximum number of strikes possible.

         In sum, a full engagement between the U.S. and Iran in the Strait of Hormuz would likely last between 37 to 112 days. The U.S. would prevail but not quickly.

         There are three policy ramifications: 1) Two special capabilities needed to re-open the strait are scarce, namely MCM assets and air defense suppression assets. There should be greater U.S. procurement of both of these assets. 2) the U.S. should expand the tanker channels so as to make mine laying less effective. 3) Since detection is the single most important aspect of the strategy, The U.S. should work more closely with friendly neighboring states to monitor Iran.


Added on: 2009-04-16 22:15:02
Précis by: James Jeff McLaren
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