During the Iran-Iraq war of the 1980s, the United States "reflagged" a number of Kuwaiti oil tankers passing through the narrow and dangerous Strait of Hormuz.  The confidence inspired by that action encouraged other tankers to make the trip, and the U.S. Navy was the guarantor of millions of barrels of oil.  Today the question of security for tankers in the Strait arises again, with Iran threatening to block the waterway. 

How might Iran accomplish this, and what resources could the U.S. bring to counter what would be understood internationally as an act of war?  (The Egyptian closure of the Straits of Tiran in May 1967 was the act of war to which Israel responded in June -- the Six-Day War.)

Iran-watchers lean heavily on the argument that Iran will not mine or otherwise damage the Strait because then Iranian oil won't be able to pass through either.  They posit that the Iranians are unlikely to take an approach that costs them oil revenue, particularly now.  But there is another possibility -- Iran can pose a threat not to the physical passageway, but to passing tankers and their crews.  And the United States Navy is not in a position to protect them.  Under that circumstance, Iranian ships could pass, but the ships of other Gulf countries could be deterred/dissuaded from trying.  The result would make Iranian oil more valuable as others withheld their supplies.

Iran could be in the catbird seat while Western navies, including the U.S. Navy, are at a considerable disadvantage even with aircraft carriers and nuclear submarines.

Over the past decade Iran has built up a naval capability that, while not "heavy" in terms of firepower, is nonetheless stealthy and dangerous.  The stealthy part comes from Iran's submarine fleet, divided into two classes -- Kilo-class diesel electric submarines from Russia, and home-built mini submarines based on a North Korean/former-Yugoslavian design.

The U.S. Navy is one of the few submarine-equipped navies in the world that does not have diesel electric subs; all U.S. submarines are nuclear-powered.  Nuclear-powered submarines are larger than conventional diesel electrics and can go farther, which is normally a plus for American forces.  But the Persian Gulf is not that big, and nuclear submarines don't have any natural advantage over diesels in this case.  Diesels can be, and are, pretty quiet when operating only on batteries, so tracking them is a challenge.

Iran has four Kilo submarines and seventeen mini-submarines known as the Ghadir.  Ghadirs are said to be equipped with a super-cavitation torpedo called the Hoot (or Whale), based on or a copy of the Russian Shkval (VA-111) torpedo.  These torpedoes are at least three times faster than conventional ones.  No oil tanker could evade them, and this type of torpedo also poses a threat to military ships.  Ghadirs, especially if all of them are deployed, may not be easy to find.  Until the threat is eliminated, oil tankers will stay away.

Adding to the problem is a large number of smaller, fast ships such as the ten Houdong-class patrol boats, or the 12 Sina class missile boats.  These ships carry C-802 sea-launched anti-ship missiles and 30mm canons.  They are fast-moving, and many of them can be used together in a fight against a larger ship.  This is a phenomenon known to naval experts as "swarming boats."

For some time now experts have been worried about the possibility of light, fast "swarming boats" stuffed with explosives in suicide attacks, overwhelming an adversary and attacking from multiple angles.  A suicide attack would be nearly impossible to stop because the firepower on most NATO ships is insufficient to knock the swarming boats out of the water.  But a swarming attack that combined light fast boats stuffed with high explosives with fast missile boats is a threat to even large American and NATO warships, including aircraft carriers.

And, while there has been a lot of talk on the subject, not much has been done either tactically or technologically to offset the threat.  In fact, the lack of firepower on U.S. ships is a very real concern in the context of protecting critical shipping lanes, especially the Strait of Hormuz.

Despite intelligence and warnings, the latest U.S. naval vessel, the Littoral Combat Ship (LCS), is equipped to do just about anything except combat.  Equipped with an undersized, unproven short-range gun and a few missiles, the LCS is outclassed by its Iranian adversary.  It is a good thing that the LCS is not ready for prime time and won't play any role in the current crisis.

For the U.S. to respond under current conditions and protect shipping lanes, it needs a lot of help from the allies in Europe, who -- despite a generally lagging ability to contribute military capabilities to a situation -- have firepower appropriate for this problem in the form of modern frigates, corvettes, and missile boats; mine-hunting ships; and plenty of good helicopters.  The allies have good submarine assets (Germany, France, the U.K., and Italy) and have long played a role in protecting sea lines of communication in the Mediterranean.

If the Iranian threat materializes, it is extremely important to assure full cooperation from NATO in order to keep the Strait open.  This requires pre-planning and coordination, but in light of the fact that our European friends are more dependent on Persian Gulf oil than is the United States, there is reason to believe that cooperation will be forthcoming.

If, in the end, Iran does try to prevent oil tankers from transiting the Strait, and if in the end the U.S. is unable to offer direct protection to ships that desire transit, there are other ways to force Iran to desist.  It would likely be ugly, and it is not to be desired, but Iran and Iran-watchers would be foolish indeed to doubt America's retaliatory capability after an act of war.

Dr. Stephen Bryen, president of SDB Partners, LLC, was deputy undersecretary of defense and the first director of the Defense Technology Security Administration.  Shoshana Bryen is senior director of the Jewish Policy Center and has more than 30 years experience as a defense policy analyst.