Iran would respond to an attack by closing Strait of Hormuz

If the United States or Israel attacked Iran, the restraint that previously characterized Iranian behavior in the strait might evaporate. Indeed, in 2006 Iran’s supreme leader, Ayatollah Ali Khamenei, cautioned that although Iran would not be “the initiator of war,” if the United States punished or attacked Iran, then “definitely the shipment of energy from this region will be seriously jeopardized.” The Iranian oil minister made similar comments, hinting that “if the country’s interests are attacked, we will use all our capabilities, and oil is one of them.” One can imagine other events that could bring Iran to the same point of desperation—for example, if it were losing a conventional war with any of its neighbors and wanted to open another front as a punitive measure or a distraction. Short of the extreme case in which the United States preemptively destroys much of Iran’s military, there is an intermediate range of scenarios in which Iran is deeply threatened yet parts of its military are still intact and functioning. It is in this context that threats to block the strait could become reality.

Yet another way Iran could drive up oil prices is by threatening free passage of oil through the Straits of Hormuz or by engaging in naval mining in the Gulf (by its surface fleet of fast boats or with its smaller submarines) and other key locations (as it did in the late 1980s). Iran has already deployed anti-shipping missiles at Qeshm, Abu Musa Island, and on Sirri Island, all of which are in range of shipping through the Strait. It has also occupied and fortified three islands inside the shipping lanes of the Strait of Hormuz -- Abu Musa, the Greater Tunbs, and the Lesser Tunbs. Given that one-fifth of the world's oil flows through the Straits (as well as roughly a quarter of America's supply of oil) and that no other nation has fortified its shores near Hormuz, an Iranian threat to disrupt commerce there would have to be taken seriously by commercial concerns (e.g., insurers and commodity markets) and other nations.

To put it briefly, the Islamic Republic has its hand on the throttle of the world's economic engine: the stretch of ocean at the mouth of the Persian Gulf known as the Straits of Hormuz, which are only 21 miles wide at their narrowest point. Through this waterway, every day, pass roughly 40 percent of the world's crude oil, including two-thirds of the oil from Saudi Arabia. By 2025, according to Energy Department estimates, fully 60 percent of the world's oil exports will be moved through this vital chokepoint.The Straits border on Iran and Oman, with the two lanes of traffic that are used specifically by oil tankers being theoretically protected by international agreement. Since 9/11, a multinational force comprising ships from the U.S., Japan, six European countries, and Pakistan have patrolled outside the Straits, in Omani waters, to make sure they stay open. But this is largely a token force. Meanwhile, the world's access to Saudi, Qatari, Kuwaiti, and Iraqi oil and gas, as well as other petroleum products from the United Arab Emirates, depends on free passage through the Hormuz Straits.The Tehran regime has made no secret of its desire to gain control of the Straits as part of its larger strategy of turning the Gulf into an Iranian lake. Indeed, in a preemptive move, it has begun to threaten a cut-off of tanker traffic if the UN should be foolish enough to impose sanctions in connection with the Islamic Republic's nuclear program. "We have the power to halt oil supply," a senior Iranian official warned the European Union last January, "down to the last drop."

Moreover, when Iran attempted to cause mischief in the strait in 1988, during the socalled tanker war, U.S. naval forces showed near-total dominance in the water, disabling six Iranian vessels and attacking two oil platforms used by Iran for intelligence monitoring. Still, Iran could take a decidedly lowtech lowtech approach to the strait, attempting at the least to raise insurance premiums on tankers traveling through it to prohibitively high levels. Raising insurance premiums (and, accordingly, the cost of petroleum products) would not require the infliction of much damage on ships, per seóit would only require that insurers become nervous that there is enough potential danger ahead that they hedge against this risk by raising premiums. Iran could attempt to use a naval version of the asymmetric warfare that the Iraqi insurgents are usingóand history indicates that if they were creative, the Iranians could cause notable damage. Such a low-tech approach would emphasize quantity, not quality, of mines. Minesweeping and detection are particularly difficult tasks, and a strategy that deployed an irregular pattern of mines would not need the use of high-tech mine-laying vessels or submarines. Mines could be dropped off the back of commercial vessels, to potentially strike oil tankers (or naval vessels) attempting to transit the strait specifically or the Persian Gulf more generally. According to Anthony Cordesman, the Iranians possessed roughly 2,000 such mines as of 2004. And during a test in July 2006, U.S. mine countermeasure vessels stationed in Bahrain were judged to have serious technical shortcomings, including dysfunctional mine warfare hardware 'hampered by cracks and leaks in equipment, damaged wires and cables, faulty indicators and exposed electrical wiring.'