Is it realistic for the US Navy to counter-block Iran’s Hormuz Strait blockade?

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LONDON – US President Donald Trump’s decision to impose a naval blockade on Iran by interdicting all ships that either come from or go to the Islamic republic provides clarity on only one point: Control over the Strait of Hormuz has now emerged as the most significant weapon in the current Gulf war.

Yet beyond that, a great deal of confusion persists over how the blockade will be enforced, and how US forces are likely to respond to its inevitable challenges.

Effectively, Mr Trump is seeking to answer a blockade with a blockade: The US President has ordered his military to start interdicting shipping in response to Iran’s initial move to close the waterway through which a fifth of all the world’s oil and liquefied natural gas passes.

The decision also came after the failure of the April 11 talks between US and Iranian officials in the Pakistani capital of Islamabad, where the question of opening the strait topped the agenda.

In his first postings on the subject on social media during the early hours of April 12, Mr Trump initially warned that the US Navy would begin the process of blockading the strait “effective immediately”. Later, however, he claimed that the blockade “will take a little while, but will be effective pretty soon”, and described it as an “all-or-none” policy.

His initial use of imprecise language prompted speculation that the US was about to stop all shipping to and from the Gulf. But this never made much strategic sense, since the US objective is not to deprive its Arab allies in the Gulf of their ability to trade, but only to prevent Iran from exporting its oil as long as the Iranians continue to prevent the Arab monarchies in the region from exporting their commodities.

It fell to the US Central Command (CENTCOM), which controls all operations in the Middle East, to clarify that “the blockade will be enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman”.

In other words, the US aim is to throttle all Iranian seaborne trade but not impede the movement of other vessels transiting to and from non-Iranian ports.

In practice, however, this may turn out to be a distinction without a difference, because the Iranians are unlikely to allow ships to get through to Arab ports if Iranian ships and cargoes are banned from crossing the same strait.

Still, what the US blockade does achieve is to deprive Iran of one major current advantage: the ability to levy fees on the tankers it allows through the strait. The shipping companies that pay such fees are already subject to listing under existing US sanctions legislation. From now on, they may also end up losing control over their vessels and their precious cargoes if they are intercepted by US ships.

Whether the US blockade is legal is a matter that will preoccupy experts for a long time; the answer largely depends on whether the US and Israeli offensive against Iran can be justified under international law. What is clear, however, is that a naval blockade against an enemy is a well-established and well-used strategy in warfare.

And it is equally clear that in practical terms, the US naval blockade signifies the end of the two-week ceasefire agreement between the US and Iran, which otherwise would have run to the end of next week.

While all hostile naval operations are fraught with danger, the challenges facing the US Navy in applying the blockade should not be exaggerated.

Retired US admiral James Stavridis, who once commanded all American troops in Europe, claims that the US will need two aircraft carrier strike groups to enforce the blockade. But the US military always wishes to over-compensate by seeking more resources.

The reality, however, is that the US has one aircraft carrier near the Gulf and another off the coast of Israel in the Mediterranean. This should be enough for the start of the operation.

Most of the blockade will take place well off Iran’s coastline, and well beyond the range of most Iranian drones. Sure, Iran can try and fire missiles at US ships, or attempt suicide missions by ramming small fast boats into US vessels. But the US Navy is more than capable of detecting and dealing with such threats, and Iran no longer has a navy to pose a sustained threat.

Nor should one exaggerate the difficulties of intercepting the slow, massive and cumbersome tankers and container ships criss-crossing the Gulf – the US will have sight of all of them well in advance of their approach. And ships that refuse to answer US calls will be boarded by US special forces and towed away.

In theory, one country may choose to order its ships to ram through the US blockade. But in practice, this is difficult to do with the kind of merchant ships in the Gulf, and an attempt to do so could also be interpreted as an act of war against the US.

A much more likely outcome is that countries such as China may lodge strong protests against the US blockade but not challenge it openly. That is what Russia does when its tankers carrying Russian oil are boarded and temporarily seized by European nations. The US military will have to think of a place to tow any seized shipping, but it is likely that CENTCOM is already making provisions for such a possibility.

The biggest weakness in the US strategy is the matter of time.

Iran is utterly dependent on its oil trade for revenue – it has few other sources of income. Its airspace is already being dominated by the US, so it is in no position to airlift any essential supplies. Most of Iran’s neighbours are also uncooperative or downright hostile to the Islamic republic. And Israeli jets have bombed Iranian naval installations in the Caspian Sea, effectively barring Russian seaborne trade with Iran.

The Iranians could, therefore, be seriously boxed in. But so is the global economy, as it faces even higher energy prices and a shortage of other commodities. The main question, therefore, is one of endurance, whether the Iranian will breaks before that of the US.

With new diplomatic feelers now in the offing, US military planners hope that Iran may de-escalate the Hormuz confrontation. If it begins to allow various tankers from Arab ports to pass the strait with no hindrance, the US may do the same with some Iranian tankers, and the immediate showdown may abate.

But once the US naval blockade is fully operational, the Iranians could also choose to escalate the confrontation instead, by hitting oil and gas installations in the Arab monarchies on the opposite shores of the Gulf.

Whatever the case may be, one thing’s for sure – that plenty of surprises lie ahead.