If Tehran crosses the Obama administration’s "red lines"—developing a nuclear weapon or blocking world oil supplies transiting the Strait of Hormuz—Washington will face a dilemma. The risks of using force are high, yet the risk of inaction may also be unacceptable. If red lines are crossed the United States must respond, but it should ponder options other than bombing.

One such option worthy of consideration: using mines around Iran's naval ports and oil-export terminals. This might create better leverage than a campaign of air strikes—without generating the death and destruction that could give Iran a cause for perpetual grievance. Mining would shut in both the Iranian navy and Iran's oil exports.

Modern U.S. naval mines are not indiscriminate weapons. They have programmable sensor-trigger mechanisms. These mines can be set to arm after a delay for a warning period, select targets based on a ship’s magnetic, pressure and acoustic signature, and they can be neutralized or cleared after a conflict.

Naval mines have advantages over air strikes. Even precision-guided weapons might well cause civilian casualties and collateral damage that cannot be undone. Air attacks against inland targets would put American pilots at substantial risk. An air campaign could not assure the complete destruction of underground targets.

Worse, mere air strikes might not provide a successful exit strategy. An exit from conflict must be based on forcing (and also enticing) Tehran to accept a political settlement ending its threatening behavior. Yet in addition to its inherent risks, a bombing campaign might cause the Iranian people to rally in support of the unpopular regime. This could further embolden Iran's leaders.

The Impact

But mining Iran's naval facilities could degrade Iran's ability to shut down the Strait of Hormuz or attack U.S. forces on patrol. Iranian minelayers, submarines and missile-armed surface ships would be trapped in their ports or unable to return to them safely.

Beyond that, mining Iran's oil-export terminals would impose considerable costs on the regime. According to the IMF, oil-export revenues account for more than 20 percent of Iran's $475 billion gross domestic product (GDP). Assuming that 80 percent of oil exports by sea can be halted by mines, and accounting only for lost oil profits, the net impact could be a loss of Iranian GDP equal to $59 billion over one year. This would be the equivalent of reducing Iran's GDP growth from today's 3 percent to around negative 12 percent.

And the impact could be even greater. Iran also imports a large portion of its refined oil products. With imports also interrupted, the total lost GDP could be in the range of $66 billion in one year. In the context of an economy that now suffers from 11 to 13 percent unemployment, this would put intense pressure on an already-divided Iranian society and its rulers.

Political decision makers and their clients in the security forces would also suffer directly. The state oil monopoly, National Iranian Oil Company, is a focal point for the governing clique's political power and patronage as well as its income. The IMF estimates that oil-export revenues account for 65 percent of total government revenues.

Pressure on the economy and on regime income would be powerful leverage for getting Tehran to the bargaining table. Mining could be extended or relaxed in response to provocation or concessions, respectively. Once an agreement was reached, Iran would likely require assistance to clear the mines. Mine-clearing assistance could be withdrawn in the case of noncompliance with terms or new provocations.

There might be other beneficial side effects. Mining only Iranian ports would leave the Persian Gulf open to other maritime traffic. Mining would stop Iran's oil exports at their source—obviating Washington's need to secure the diplomatic and financial cooperation of Iran's many trade partners. Effective American action might persuade Israel to refrain from launching its own attack on Iran (which could spark wider Middle East conflict).

The United States has allowed most of its offensive mining capability to atrophy, but it retains the ability to conduct some naval mining. Quickstrike mines are dropped from aircraft, like traditional iron bombs. They rest on the bottom in shallow waters and are activated by the signature of a vessel passing overhead. Their triggers can be optimized for selected targets, and they do not float into sea-lanes.

Better than Bombs

Mining Iran's harbors would not be a political-military panacea, and it would entail risks. Naval mines are legitimate weapons of war, but there are international conventions governing their use. Advance warning to neutral ships, partners and allies might be required. Mine-laying aircraft must be protected. As in any conflict, Iran would seek ways to retaliate, possibly with terror attacks, missiles or small craft too light to trigger mines. Similarly, in any conflict the world would need to find substitutes for Iranian oil supply. The core response to these varied objections is the same: if the United States is obliged to use force, mining naval bases and oil-export facilities may be more effective, less risky, and inflict fewer casualties than other options alone, and it might help bring Iran to the negotiating table.

Even the threat of U.S. offensive mining against Iran's ports might help the United States avoid conflict by deterring Iranian provocations.

George J. Gilboy is a Senior Fellow at the MIT Center for International Studies. He is the coauthor, with Eric Heginbotham, of Chinese and Indian Strategic Behavior: Growing Power and Alarm (Cambridge University Press, 2012).

Image: Marion Doss