President Trump has expressed frustration over the hesitancy of key allies to help reopen the Strait of Hormuz. But, given the operational challenges and the politics, putting together an international operation is unlikely to be quick or easy.

President Donald Trump is not hiding his frustration that some of the United States’ European allies have been reluctant to heed his call for them to send ships and other forces to help reopen the Strait of Hormuz. He reserved particular criticism for the United Kingdom. European leaders in turn have made it clear they do not want to be drawn directly into the current conflict. The UK prime minister, Sir Keir Starmer, has said that allies are seeking ‘a viable plan’. But what that would look like is far from clear. And recent experiences of trying to put together maritime-security operations in this region, notably to counter the Ansarullah (Houthi) anti-shipping campaign in and around the Bab el-Mandeb Strait and the Red Sea, have highlighted the difficulties involved.

A chokepoint like no other

The latest events have been a salutary reminder that not all strategic maritime chokepoints are equal. The Strait of Hormuz may be one of the most critical.

When the Houthis threatened shipping in the Bab el-Mandeb Strait from November 2023, the dire economic consequences that were forecast did not materialise, in part because shippers could reroute around the Cape of Good Hope. There was also sufficient shipping capacity to cope, and markets adapted. The Strait of Hormuz is different. It accounts for 20% of all internationally traded oil, 34% of seaborne oil-trade flows and 30% of liquefied natural gas exports. It is also the only maritime route in and out of the Gulf.

There are pipeline alternatives, but they have only about one-third of the capacity that normally flows through the Strait of Hormuz. There have long been calls to build more pipelines, and even a canal, to bypass the strait. However, building sufficient capacity would be a challenge. And recent events have shown that canals and fixed land-based energy infrastructure have their own vulnerabilities.

The asymmetric challenge

The US Department of War has pushed back against criticism that it underestimated the threat of closure of the strait. After all, that threat has certainly cast a shadow, and has therefore been on the minds of Western naval and military planners for decades.

Nonetheless, keeping the strait open, or reopening it, in the face of a military confrontation with Iran has always looked like a military challenge, and one that seems to have become potentially more difficult over the years. As the US chairman of the Joint Chiefs of Staff, General Dan Caine, put it rather drily in the face of calls to escort threatened shipping, it is a ‘tactically complex environment’.

The US has made much of the extent to which it has degraded Iran’s naval capabilities. But many of these successes have been against what might be described as Iran’s more conventional naval assets. It has long been acknowledged that the main threat to shipping in the Strait of Hormuz and the Gulf more widely comes not from Iran’s conventional navy but from its considerable array of land-based anti-ship missiles and its unconventional and asymmetric arsenal of one-way attack uninhabited aerial vehicles (UAVs), swarms of small attack craft and potentially uncrewed surface vessels, midget submarines, and limpet and other naval mines.

Clearly, US forces have been going after these as well. US action may degrade the threat but, as with the Houthi threat previously, it may not eliminate it – a fact now recognised, it seems, by President Trump. There would still be the possibility of pop-up attacks using missiles, UAVs, or mines that the Iranians might hope to sow surreptitiously from otherwise innocent-looking dhows.

Even for the US Navy, escorting commercial ships in the current circumstances, with major combat operations still ongoing, would be a significant ask. It would divert naval resources from other missions and probably also require substantial air support. Even then, the constrictions of the strait – just over 30 kilometres wide at its narrowest point – would still draw US Navy warships into a situation where warning times of attack are short and their own capability advantages reduced.

The US will probably have been mounting extensive surveillance missions to try to forestall, deter or counter as much Iranian activity at sea as possible. The attacks so far on Iran’s critical Kharg Island oil terminal, and the threat of more to come, appear to be a further effort at dissuasion. The reported dispatch towards the region of more US warships in an amphibious ready group led by the big-deck amphibious-assault ship USS Tripoli, with more than 2,000 US Marines aboard, may be a signal of preparations for a future mission that could include raids on shore-based threats around the strait, or even on Kharg Island.

And it is not just about the strait. Iran has an extensive Gulf coastline from which to launch anti-shipping strikes, as its targeting of oil tankers in the north-west corner of the Gulf demonstrated.

Another lesson from the current situation, as during the Houthi campaign, is that despite many years’ experience of cooperating in the face of more limited threats at sea, such as Somali piracy, there is still a gulf of understanding that needs to be bridged between the policymakers and the military, on one hand, and shipowners and operators, on the other, over what navies today can actually deliver in terms of protection and what the shipping industry seeks in terms of reassurance.

Naval coalition of the willing or wilting?

In European capitals, the operational risks will look formidable. President Emmanuel Macron of France led an initial call for a protection effort, with the promise of multiple French warships, but only after the worst of combat operations had died down. While the European Union marshalled a force for the Red Sea to protect commercial shipping from the Houthis from February 2024, only a handful of countries actually sent warships, they operated under very restrictive defensive rules of engagement, and most of the time the force could muster just two or three vessels. There appears no appetite right now for taking on an even more challenging mission in the Gulf.

The stakes may now be higher, but so too are other demands closer to home, while the availability of assets is limited and the pool of warships with the right capabilities even more so, given that even Iran’s residual capabilities may be more threatening than those faced in the Red Sea. The UK may be uniquely embarrassed by the timing of this conflict. It spent decades maintaining a naval presence in the Gulf, which until recently included a frigate, four mine-countermeasures vessels that were considered a ‘crown jewel’ capability, and an auxiliary mother ship. None of these remain (except the frigate, which is decommissioned and awaiting disposal).

The UK has some limited remote mine-countermeasures gear and specialist personnel in the region. But these would still require host vessels from which to operate effectively. It has also been developing newer autonomous mine-hunting systems, which might be deployed.

The US, likewise, recently withdrew its four traditional anti-mine vessels based in the region. It replaced them with three littoral combat ships with mine-countermeasures gear aboard, but this is a capability unproven in combat and the ships would also require protection. Indeed, they now appear to have been withdrawn out of harm’s way. Again, the hope would be that major combat operations would be reduced or ended before undertaking a full-scale clearance mission.

Among the Arab Gulf states, Saudi Arabia and the United Arab Emirates have some mine- clearance capabilities. Several European countries have capable mine-warfare forces, as do other potential players, including Japan. But whether they would want to deploy forces in the current circumstances, and when they would be prepared to do so, may be open to question. The same holds true on the wider escorting issue. The bulk of Gulf oil is destined for Asia. But here too, willingness and ability to deploy quickly into a ‘hot’ war zone is clearly an issue.

Beyond operational concerns, the political cross-currents at play are a further complicating factor. These, especially a desire not to be too closely associated with US policy or operations, have affected responses to all the recent threats to navigation in the region: the 2019 disruptions of shipping in the Strait of Hormuz in the wake of the previous Trump administration’s ‘maximum pressure’ policy against Iran; the recent Houthi campaign; and now this conflict. The responses on those previous occasions were sub-optimal, with different missions operating under different rules. A combination of capability shortfalls and political sensitivities were also behind the fact that the major regional players essentially did not turn up in the Houthi case. They will now be weighing difficult choices again.

Charting the right course

President Trump has stated that the strait will be reopened one way or another, and that some countries at least are keen to help. Although he has asserted that the US does not in fact need the help, attempting to go it alone on a potentially extensive mission would add serious strain to the US military machine. Given the stakes, some form of coalition mission or missions may well emerge. But just what the commitment will be, and when, remains uncertain. European leaders emphasise de-escalation and a defensive approach to any mission. They will be looking for more assurances of reduced combat operations and threat. At the same time, while aiming for separation from US operations, they will no doubt seek US ‘top cover’ with surveillance, air support and missile defence to fill the capability gaps the Europeans have. These factors alone create a challenging operational and political minefield.

Some level of unease and disruption may persist. If Tehran were able to sow a significant number of mines, these could take weeks or months to clear. Much will depend on what level of confidence ship operators feel they need in order to begin transiting again, which is another factor that may be difficult to gauge. Tehran may opt for a continuing maritime insurgency using asymmetric forces, including mines, missiles and UAVs, with sporadic nuisance attacks over an extended period. Such a strategy could soak up valuable Western and other naval forces for a prolonged period. And a naval mission is not a panacea when it comes to restoring stable energy and other maritime trade.