Can the US protect the Persian Gulf if Iran wants to target tankers?

The Explainer

Tensions between the United States and Iran are rising due to a rash of attacks on a half-dozen oil tankers traveling through the Persian Gulf region over the past several weeks.

Most recently, two tankers in the Gulf of Oman were struck by explosions on June 13. President Donald Trump has blamed Iran for the incidents, and the Pentagon released grainy video footage it says shows Iranian forces removing a limpet mine from the side of one of the ships. Iran denies any role in those attacks or the damage done to four other ships in May.

The exchange comes amid the standoff over the United States’ withdrawal from the Iran nuclear deal – the landmark 2015 pact between Iran and six world powers that curtailed Iran’s nuclear program in exchange for lifting sanctions. Mr. Trump, who had been very critical of the deal, unilaterally pulled the U.S. out in May 2018. He then began a “maximum pressure” campaign against the Islamic Republic, imposing crippling sanctions in a long-shot bid to force Iran to accept a more restrictive nuclear deal with the U.S.

What makes shipping in the Persian Gulf vulnerable to attack?

The key factor is the narrow confines of the Strait of Hormuz, an ocean chokepoint that connects the Persian Gulf to the Indian Ocean. About one fifth of the world’s oil is transported through the strait, which is bordered by Iran and the United Arab Emirates.

The strait tapers to only 21 miles across at the slimmest point, where shipping lanes in both directions shrink to just two miles wide, largely because the water is too shallow for ships with deep drafts. The V-shaped strait requires tankers to make a sharp turn at a predictable point – making them easy to target with mines, small surface ships, or shore-based missiles or aircraft.

How does the U.S. maintain security in the Gulf?

The U.S. Navy’s Fifth Fleet, headquartered in Bahrain, maintains a constant presence in the Persian Gulf using patrol vessels, guided-missile destroyers, and mine countermeasures vessels. It is part of a combined maritime force that brings together Gulf partners as well as European and Asian allies. The U.S. also monitors the region with satellites and aerial drones to identify threats.

Yet despite the continual U.S. and allied patrols, more precise reconnaissance is required to prevent what experts view as the main threat to the shipping lanes: mines.

“The biggest threat is the mine threat. Not the limpet mines, but distributing mines in the water. Countermine operations are very difficult for any navy. It’s a painstaking process,” says Dr. Mike Connell, an expert on Iran and the Middle East at CNA, a research organization in Arlington, Virginia.

Preventing the placement of mines in the water or directly on ships would ideally involve maritime patrol aircraft. “The problem is they can’t be everywhere,” says Dr. Connell. “To get that level of precision is difficult. The amount of area to cover takes a lot of reconnaissance assets.”

How could the U.S. bolster Gulf security?

One option is for the U.S. Navy to escort convoys of merchant ships to help defend them from attack. From its current fleet, the U.S. Navy would employ destroyers or cruisers for this job. “A convoy would assemble at a designated place to let the number of available naval escorts spread their defenses across the maximum number of vessels,” says James Holmes, J.C. Wylie Chair of Maritime Strategy at the Naval War College. The warships would provide protection against gunfire and missiles aimed at the tankers.

The U.S. Navy provided such escorts during the 1980s Tanker War, when Iraq and Iran were attacking each other’s merchant ships. The escorts could go hand-in-hand with mine-sweeping operations aimed at detecting and clearing mines from shipping lanes.

However, the U.S. Navy has only a limited number of suitable warships available for such escort duty, making it difficult to sustain for long periods. “That’s a hole in the force structure that cries out to be filled,” says Professor Holmes.

In the meantime, U.S. allies could provide additional warships for escorting merchant ships. Saudi Arabia has stepped up security around oilfields, while the United Arab Emirates is working with shipping companies to provide increased protection, according to Reuters.

For their part, shippers do not always view convoys and naval escorts as the best solution to the security threats. Convoys cause delays, inefficiencies, and transaction costs for their business. As a result, shipping firms have taken unilateral steps to bolster their self-defense capabilities. Some are employing armed guards.

How could Iran disrupt shipping in the Persian Gulf?

Aware that it is no match for a direct confrontation with American military forces – U.S. defense spending is roughly 50 times that of Iran’s – the Islamic Republic has for decades developed a strategy of asymmetric warfare and spent years practicing closing the strait.

In the Persian Gulf, that means using everything from swarm attacks with hundreds of speedboats, to anti-ship missiles, submarines, and underwater drones. Iran’s Islamic Revolutionary Guard Corps (IRGC) frequently displays its capabilities in military exercises.

Such tactics have proven effective, most famously in a classified $250 million U.S. war game in 2002. In a coordinated assault with swarming boats and missiles, the “enemy” team “sunk” 16 American ships, including an aircraft carrier, before the exercise was suspended.

U.S. strategists have since updated their tactics. But Iran, too, has stepped up its capability, proclaiming the use of high-speed torpedoes and stealth technologies. Yet the core of its tactics in the Persian Gulf are mines, speedboats, and missiles, one official news agency reported last September.

“The IRGC has a successful record in using those techniques, which is why it is directing all its capacities to boosting them,” it said. 

How far can this game of Persian Gulf brinkmanship go?

Both the U.S. and Iran explicitly state that they don’t want war. But the White House portrayed the deployment of a U.S. Navy carrier group to the Middle East in May as pushback against Iran and vowed “unrelenting force” should Iran attack.

Likewise, after adhering to the terms of the nuclear deal for a year after the U.S. withdrew, Iran has started to increase its rate of uranium enrichment and declared it will breach agreed limits on June 27 if nothing changes.

That is one part of Iran’s reaction, while a second is in the Persian Gulf, says Nasser Hadian, a political scientist at Tehran University.

“Tension is going to rise,” says Mr. Hadian. “Iran is certainly not going to close down the Strait of Hormuz; they will ... concentrate on oil and petrochemical ships. They are going to stop them. They are going to inspect them. They are going to create all sorts of problems, and that’s in response to the U.S. policy of sanctions.”

Any actual attacks would be “open and transparent,” he says, and not shrouded in secrecy as the latest tanker explosions were, to make any message of deterrence clear. Pressure will grow too on U.S. allies the United Arab Emirates and Saudi Arabia, which take a hard line against Iran.

The coming weeks may therefore see a sizable Iranian military deployment along the Persian Gulf and into southwestern Khuzestan province, Mr. Hadian says, to “send a strong signal that our threats are credible.”

“My guess would be, as soon as Iran deployed forces, it doesn’t need to do anything else,” says Mr. Hadian. “That would be good enough to increase tension, thus increasing the oil price, thus changing the calculus of Trump.”