When Iran's vice president, Mohammad Reza Rahimi, declared on Dec. 27 that "not a drop of oil will pass through the Strait of Hormuz" if Western countries followed through with threats of escalated sanctions over its nuclear program, the world sat up and took notice. Since then, tensions have run high in the Persian Gulf, with Iran holding naval exercises and U.S. Secretary of Defense Leon Panetta warning Iran that closing the strait would be a "red line" for the United States.
Newspaper headlines are warning of a possible conflict breaking out over one of the most important shipping lanes on the planet, through which almost 20 percent of the world's oil passes each day. Analysts and commentators can't seem to decide how seriously to rate this risk: They have generally argued that Iran's military (and especially naval) capabilities are either insignificant or extreme threats to U.S. and allied forces in the region. So which is it? Is the Iranian navy as dangerous as it claims to be? Can Iran really shut the Strait of Hormuz?
The truth is that Iran does possess a number of tools to harass, challenge, and even harm opposing naval forces, but its overall arsenal is limited, ramshackle, and untested in combat. Iran's military commanders know that their naval capabilities are ill-suited for direct engagement with U.S. forces. Iranian traditional naval vessels and aircraft are no match for their American counterparts, and Iran possess too few of both to endure any extended engagement. Unable to challenge U.S forces with equal strength and firepower, Iran's military planners have designed "asymmetric" tactics that utilize the greater speed and agility of their maritime assets. Iran's small boats and midget submarines would be central to any Iranian naval engagement, and are likely the ones that would be the most difficult to initially counter. Iran has also produced thousands of naval mines, which could be littered throughout strategic sea lanes in the Persian Gulf or employed as defensive measures around key Iranian maritime infrastructure. The United States has the capability to effectively deal with naval mines, but their use by Iran would certainly complicate maritime traffic for a period of time.
This asymmetric approach to warfare, which is borne out of Iran's longstanding technological disadvantages vis-à-vis the United States and its allies, is the military basis for its particular threat to close the Strait of Hormuz. Iran cannot compete with U.S. forces directly, but the collective marshaling of its maritime assets (mines, small boats, midget subs, etc.) could severely test the United States' ability to maintain security in the Persian Gulf. Closing the Hormuz strait -- or more likely, creating a hostile environment in the Gulf that leads to a drastic decline in maritime shipping through it -- is probably the most extreme and certainly the most politically and economically damaging act that Iran's maritime forces could achieve. While the impact this would have on Iran, the United States, and Arab states in the region, is debatable, Iran understands that few if any would like to find out. This is Iran's answer to the United States' "all options on the table," and for all of its saber-rattling and exaggerated bluster, is something its forces could accomplish.
Yet, as Chairman of the Joint Chiefs of Staff General Martin Dempsey recently stated, Iran's ability to keep the strait closed or constricted would likely be short lived. Because of the military operations that would be involved, and the damage it would do to the economies of the region, closing the strait would likely be considered an act of war against the United States and its Gulf allies. U.S. retaliation against Iran would thus be a near certainty, putting at risk much of Iran's maritime and littoral military assets. The United States could end up destroying much of Iran's navy, air force, and land based artillery just to clear the way for re-opening the strait. The United States might also take the opportunity to target Iran's nuclear sites, if not move to topple the Iranian regime altogether. Regional opinion (especially that of the United States' Arab allies) will most likely support military operations in such a context, and the international community will be hard-pressed not to support military action against an Iran that is willing to jeopardize world petroleum and gas markets for its own political purposes.
None of this means Iran's bluster should be dismissed. Iran has the capability to challenge U.S. naval forces and the ability to close the Strait of Hormuz, albeit for a limited period. There is no question that U.S. commanders take the threat that Iranian forces pose seriously. However, while Iran might have an advantage in limited, asymmetrical attacks, that advantage quickly dissipates in an open and extended conflict. A war with the United States -- especially if it included an Iranian attempt to close the Hormuz strait -- would have devastating effects on Iran's economy, military, regional relations, and international standing. Thus, initiating a conflict with U.S. forces, particularly a maritime conflict, would be a last-ditch, kamikaze act by the Iranians. Iranian leaders understand this, which is why their strategy up until now has been focused on preventing outright conflict with the United States.