WASHINGTON -- In his televised 9/11 address, President Bush said that we must not ``leave our children to face a Middle East overrun by terrorist states and radical dictators armed with nuclear weapons.'' There's only one such current candidate: Iran.

The next day, he responded thus (as reported by Rich Lowry and Kate O'Beirne of National Review) to a question on Iran: ``It's very important for the American people to see the president try to solve problems diplomatically before resorting to military force.''

``Before'' implies that the one follows the other. The signal is unmistakable. An aerial attack on Iran's nuclear facilities lies just beyond the horizon of diplomacy. With the crisis advancing and the moment of truth approaching, it is important to begin looking now with unflinching honesty at the military option.

The costs will be terrible:

Economic. An attack on Iran will likely send oil prices overnight to $100 or even to $150. That will cause a worldwide recession perhaps as deep as the one triggered by the Iranian revolution of 1979.

Iran might suspend its own 2.5 million barrels a day of oil exports, and might even be joined by Venezuela's Hugo Chavez, asserting primacy as the world's leading anti-imperialist. But even more effectively, Iran will shock the oil markets by closing the Strait of Hormuz through which 40 percent of the world's exports flow every day.

Iran could do this by attacking ships in the Strait, scuttling its own ships, laying mines or just threatening to launch Silkworm anti-ship missiles at any passing tanker.

The U.S. Navy will be forced to break the blockade. We will succeed but at considerable cost. And it will take time -- during which time the world economy will be in a deep spiral.

Military. Iran will activate its proxies in Iraq, most notably, Moqtada al-Sadr's Mahdi Army. Sadr is already wreaking havoc with sectarian attacks on Sunni civilians. Iran could order the Mahdi Army and its other agents within the police and armed forces to take up arms against the institutions of the central government itself, threatening the very anchor of the new Iraq. Many Mahdi will die, but they live to die. Many Iraqis and coalition soldiers are likely to die as well.

Among the lesser military dangers, Iran might activate terrorist cells around the world, although without nuclear capability that threat is hardly strategic. It will also be very difficult to unleash its proxy Hezbollah, now chastened by the destruction it brought upon Lebanon in the latest round with Israel and deterred by the presence of Europeans in the south Lebanon buffer zone. Continued...