Paul William Roberts provides a scenario in today's Globe & Mail. The essay is behind their subscription wall, so here's the summary of what Roberts says:
The US scenario of an attack on Iran is that their nuclear facilities would be bombed and that Iran will grimace and take its medicine.
The Iran scenario plays out differently - "the one most likely playing to thunderous applause in the corridors of theocratic poser on Qom and Tehran" -- is that Iran has already promised to retaliate and there are nearly 1000 missiles in place that could be fired at targets around the Persian Gulf such as ships, airbases, refineries and oil terminals.
Supertanker traffic through the Gulf would halt for weeks, thus stopping 25 percent of the world's oil supply.
China and Japan would be miffed, and could vent their displeasure by dumping a few billion dollars from their foreign currency reserves to offset dolar-based oil prices by forcing a week dollar even lower.
In Iraq, the resistance would increase their attacks because US planes will be busy over Iran "which may explain why US forces there have been consolidating their bases recently." Iran would have "little compunction" about sending to Iraq "killing machines much more advanced than what they currently provide...thus far they have been cautious not to send anything easily traceable...once the bombs fall, though, the gloves will come off, and we can expect to see in Iraq such weapons as .50-calibre rifles able to punch through body armour, multiple rocket launchers, and newer kinds of shoulder-fired anti-aircraft missiles..."
Iran might blockade the Straights of Hormuz with sea mines and attack boats, and by sinking ships. "Around 40 per cent of the world's crude passes through this two-mile-wide channel, where Iranian forces are already situated, ashore at the head and on heafily fortified islands...in 1999, Iran deployed its new Russian-supplied Kilo-class submarines as part of a plan to block the Straits in times of crisis. The subs were to be used to lay mines and fire advanced torpedoes at ships attemtping to enter or leave the southern Gulf." And nearly all US military supplies to Iraq are shipped through the Persian Gulf. So if the US tried to secure the Straits by a major US amphibious landing, such an effort would need somewhere around 30,000 US troops and would involve weeks of combat.
In conclusion, Roberts speculates,
What would happen though if the invasion stalled and the straits were not reopened swiftly? The emergency oil stocks utterly vital to the economy of the industrial world would begin to run out, along with supplies to some 150,000 US troops stranded in Iraq and Kuwait. It is then not at all far-fetched to contemplate history's most ignoble and empire-quashing retret through the deserts of Iraq and Jordan and into Israel, particularly if thousands of Iranian soldiers pour into Iraq to assist in the attacks on US military camps.Roberts ends the essay by noting that it should be expected that defusing the tense situation with Iran could be done through diplomacy.
These, then, are the chilling facts that have made Iranians so cocky of late...and it is hard to say why they should not feel so self-assured. It truly is a MAD scenario, son of the Cold War, thus one only a lunatic would contemplate. The risks are too grave, the benefits not at all clear.
This will be wearyingly obvious to most world leaders -- except those in Washington, where it has become increasingly difficult to distinguish between arrogance and ignorance.