The Islamic Republic of Iran recently issued a blatant threat to close the Strait of Hormuz, the choke point at the southern extremity of the Persian (or Arabian) Gulf through which passes 30 percent of the world’s oil production. The warning came on the heels of poor domestic economic news, violent political unrest and dropping oil prices. The stated reason for the threat was the impact of renewed U.S. economic sanctions on Iran’s ability to maintain its share of the international oil market.

Certainly, were Iran to make good on its threat, the effect would be seen in the world price of crude oil. While much of Saudi Arabia’s crude exports could continue through pipelines to the Red Sea port of Yanbu, the export of oil from the UAE and Kuwait, for example, would likely stop. But it is useful to examine the feasibility of the threatened closure and the likely consequences for Iran.

In the first place, closing the 26-nautical-mile waterway could entail Iranian aerial attacks on civilian and military shipping. A second, and apparently favored, tactic might be to use “swarms”of small boats (Swedish-built Boghammers) that the Iranian Revolutionary Guards have in abundance. Alternatively, the Iranian military has the capabilities to attack shipping in the southern Gulf with anti-ship cruise missiles from islands on the eastern side of the Persian Gulf.

Finally, the least attractive options would be to either mine the Strait or to employ submarines and the rather small number of surface combatants in the Iranian navy — as distinct from the Revolutionary Guards. Mining the Strait would also complicate Iranian oil exports to important customers such as China. Deploying conventional naval assets to deter passage might be deemed useful to signal seriousness of intent or as a deterrent to countermeasures by the U.S., but these tactics would have short-lived and catastrophic consequences for the “regular” Iranian navy.

In fact, the problem with all of these options is that they can be trumped and defeated. The U.S. and its Arab and European allies (and perhaps even the Japanese) could quickly mount offensive operations to keep the Persian Gulf open with devastating results for Iran. Moreover, since the closure of an international waterway is a flagrant act of war, Iran may open itself to threats well beyond Hormuz. Among them might be actions to neutralize their coveted ballistic missile capabilities, and yes, their long-concealed military nuclear sites.

In any event, the ayatollahs will want to to apply their calculus very carefully before making good on their threats.

Philip A. Dur, Ph.D., is a U.S. Navy Rear Admiral (retired) and a Destin resident. He can be reached at