Any attempt by Iran to disrupt shipping in the Strait of Hormuz would prove too costly, both economically and militarily.
Iran has options, but odds are against it in Strait of Hormuz
The Maritime Security and Surveillance conference held in Abu Dhabi at the end of January could not have come at a more relevant time.
Dealing with all issues of maritime security, from trafficking to piracy, the conference also touched upon issues of significance to the developing tension in the Strait of Hormuz.
That friction came to a head in late 2011, as Iran held the Velayat 90 naval exercises. The stated goals of the exercise were to practise (and presumably demonstrate) the ability to close the Strait of Hormuz if necessary. Since then, the EU's decision to place a six-month delayed embargo on Iranian oil exports has been countered by Tehran's repeated threats to close the strait.
The main question for those wishing to avoid such an outcome, therefore, is whether Iran does indeed possess the capabilities to close the strait to commercial or non-Iranian shipping. The answer is yes, temporarily, but the effects would be so grave that it may prove unpalatable for even Tehran.
There are two primary ways for Iran to disrupt shipping through the strait. The first is to use missiles, rockets and torpedoes to directly attack vessels transiting through the chokepoint. The second is to mine areas of the strait to make it inaccessible.
The missile threat is certainly the most aggressive. Iran showcased some of its Chinese-supplied anti-ship missiles during Velayat 90 in a suggestion that they could be used in any strait closure, and the weapons themselves are certainly capable of targeting, hitting and sinking commercial vessels within 150km of the launch platform. Those platforms could either be mobile truck-trailers on Iran's shore, or some of the hundreds of small, fast attack craft the Iranian Navy and Iranian Revolutionary Guard Corps maintain.
The problem for Iran is that a clear indication of the possibility of missiles being used may encourage the United States and allied European and Arab states to undertake a convoy system for the most strategic vessels passing through the strait.
Given that an average of 14 very large crude carriers passed through the strait per day in 2011, it is feasible that these ships, and any LNG carriers, could be grouped in a few convoy transits. Such convoys might not provide total coverage: even the missile defence systems on the US Fifth Fleet's cruisers and destroyers may struggle with several fast attack craft attacking in a swarm while shore-based launchers and artillery pieces fire further ordnance and submarines attack with torpedoes.
But a guarded convoy would offer a robust defence and, perhaps more importantly, signal the United States' determination to protect shipping. This latter point would suggest that the US navy might even undertake the kind of retributive action seen during the Tanker War in the 1980s, when Operation Praying Mantis destroyed several vessels from the Iranian navy as tensions escalated after a US frigate was crippled by an Iranian mine.
Reflagging the convoyed vessels as US ships, as happened when US warships escorted convoys in 1987 and 1988, would be an even stronger sign of intent: in international law, an attack on a ship is seen as an attack on the flag nation itself.
To avoid this direct confrontation with the United States, Tehran might prefer to lay mines throughout the strait. It certainly has enough to disrupt some shipping. Best estimates of Iran's arsenal suggest between 2,000 and 3,000 mines, which could be laid by submarines, small craft and commercial vessels.
Moreover, mines have a disproportionate effect on shipping, as just one mine can deny a large area of sea to commercial vessels that fear for their safety, while mine-clearance operations can take days, if not weeks, to open up mine-free corridors.
The problem for Iran in this strategy, though, is that mining the strait would effectively close it to Iranian shipping as well. Missiles, rockets and torpedoes discriminate in their targets; mines do not. Given Tehran's reliance on oil revenues, with up to 70 per cent of government revenue coming from oil exports, and its inability to shift oil exports to its Indian Ocean ports, this would have a severely negative effect on its already struggling economy.
Other options exist: Iran could launch a suicide small boat attack on a tanker in the strait, like the failed attack on the Japanese oil tanker the M Star in the strait in July 2010, in a bid to cause a disruptive oil spill, but that also would have the indiscriminant effect of closing the area to all shipping.
Alternatively, Iran could attack shipping further inside the Gulf and even at anchor, where vessels would be more vulnerable, and farther from the possible concentration of US and allied forces in the strait. The effects of this would be less dramatic than closing the strait, but easier to accomplish.
But in the final analysis, any attempt to disrupt shipping in the strait might prove either too costly to Tehran or too dangerous if it forced a US reaction.
Christian Le Mière is a research fellow for naval forces and maritime security at the International Institute for Strategic Studies