The U.S. Fifth Fleet insisted June 30 that it would not allow Iran to "shut" the Strait of Hormuz following a thinly veiled threat June 28 by Maj. Gen. Mohammad Ali Jafari, commander of Iran's Revolutionary Guard Corps, to do just that. This back-and-forth rhetoric makes it worthwhile to examine Iran's military capability along this vital international waterway. The Strait of Hormuz is 21 miles across at its narrowest. The shipping traffic corridor itself is a mere 6 miles wide, with 2 miles each for incoming and outgoing traffic, separated by a 2-mile buffer. More than 90 percent of all oil exported from the Persian Gulf, or nearly 17 million barrels per day (bpd), transits this outgoing lane. This is nearly two-fifths of the world's oil supply. If the strait were closed, only about 3 million bpd of that could realistically be redirected through Saudi Arabia via a trans-Arabian pipeline.