Since the US withdrew from the 2015 Iran nuclear deal and began re-imposing economic sanctions last year, Iranian officials have variously threatened to close off the Strait of Hormuz, through which roughly one-third of the world’s seaborne oil is traded. These threats started to appear more salient in May and June, when attacks were reported on six tankers in the Gulf of Oman and near the coast of the UAE. In one instance, surveillance footage appeared to show members of the IRGC pulling up next to one do the vessels after it had been abandoned due to an explosion, whereupon they removed what was believed to be an unexploded limpet mind.

Almost immediately after those attacks, the IRGC shot down a American surveillance drone, in an apparent effort to impede efforts at observing further escalatory actions in the area of the Strait. All of this has contributed to a situation in which the US is working to secure commitments from regional allies and global trading partners for naval patrols in the Persian Gulf aimed at preventing further Iranian attacks. As details continue to emerge, the apparent seizure of the Riah may serve to raise additional awareness about the seriousness of those threats, thus bolstering the White House’s campaign.

Already, it has been reported that the British Royal Navy is deploying a third warship to the region, although London insists that this deployment was already planned as part of routine asset rotations and is unrelated to the escalating tensions with the Islamic Republic. Nevertheless, the reports underscore the fact that the United Kingdom has significant military forces already in the region and shortly on their way, which could contribute to the planned coalition if European efforts at de-escalation prove unsuccessful.

It is also worth noting that the UK’s statements on the deployments somewhat mirror those made by the US in April, regarding the then-pending arrival of the USS Abraham Lincoln aircraft carrier. At the time, Bolton stated that the deployment was ordered in response to intelligence regarding the potential for imminent Iranian attacks. Other sources later explained the ship’s deployment to the Middle East had already been planned ahead of time, but the timetable for that deployment was reportedly accelerated after the relevant intelligence was revealed.

Whereas the US arguably overstated the relationship between Iranian threats and the given naval deployment, it is possible that the UK is understating the relationship between newfound threats and a very similar deployment. This would be in keeping with the current posture of most European governments, including that of the UK and the other two signatories to the Iran nuclear deal.

Britain, France, and Germany have all been working to preserve the agreement ever since the American withdrawal, and have accordingly been hesitant to upset the Iranian leadership. But at the same time, those governments have also expressed serious concerns about Iran’s provocations, and those concerns have naturally grown as Tehran has transitioned from arguably empty threats over the Strait of Hormuz to open aggression against regional and Western adversaries.

This general situation lends credence to the interpretation of Britain’s latest naval maneuvers as being on some level a response to Iranian activities. And this is made all the more credible by the fact that the disappearance of the Riah tanker, if proven to be an act of retaliation, was most likely an act of retaliation against the British in particular. The incident came just roughly a week and a half after British Royal Marines seized a tanker carrying Iranian oil. While the cargo itself may have been grounds for an enforcement request from the US government, the ultimate justification for the seizure was that the oil was intended for sale to refineries affiliated with the regime of Syrian dictator Bashar al-Assad, which is under sanction by the European Union for human rights violations.

Tehran has refused to recognize the legitimacy of that seizure under international law, and this narrative underlay a number of threats of retaliation that were voiced by Iranian officials and IRGC commanders in the run-up to the Riah incident. On Wednesday, Iran’s vice president for legal affairs issued a report formalizing this narrative and insisting that the UK had no grounds for enforcing the relevant sanctions because “the European Union’s unilateral sanctions are not binding for countries outside of the EU.”

The report goes on to explain that the ship alleged to be carrying Iranian oil, the Grace 1, was Russian-owned and Panamanian-flagged, putting it beyond the reach of EU jurisdiction. But this argument could create additional problems for Iran in the wake of its own retaliatory action. The Riah is also foreign-owned and Panamanian flagged, so there is no clear reason why Iran should perceive its seizure as being more lawful. Whereas the Riah was lawfully passing through Iranian territorial waters, the Grace 1 was seized was passing by Gibraltar, which is controlled by the UK, putting the incident squarely in British waters.

Furthermore, the rationale for the July 4 seizure was clearly outlined in advance by the British. In contrast, the Iranians have given no explanation for the seizure of the Riah. In fact, they have expressly denied that the incident comprised a seizure in the first place. This serves to preserve Iran’s claim to legal standing in the case of the Grace 1, although that effect is unlikely to last long. The regime’s cover story regarding the Riah experiencing a malfunction and receiving help from Iran is made implausible by several facts.

Firstly, no other country reported receiving a distress beacon from the ship. And even if one had been sent, there is no obvious reason why the crew would have decided to turn off the ship’s transponder, thereby making its course of travel unknown to anyone not on-site. Finally, even amidst growing suspicion from the US, the UK, and other world powers, Iran has made no effort to inform the world of the location or conditions of the 25 crew members on board the Riah. The sailors themselves have apparently not been permitted to contact their homes, either.

This situation is not unique in the recent history of the Islamic Republic. In January 2016, two US Navy boats strayed into Iranian territory during a training exercise, leading to 10 sailors being arrested and detained for 15 hours, during which time their images were extensively broadcast via Iranian propaganda networks. The IRGC members involved in the incident were later given Iran’s highest military honors and a statue was commissioned to commemorate the arrests.

Amidst the current regional tensions, and following two tanker explosions for which Iran is presumed responsible, Iranian gunboats surrounded the commercial vessels that first rescued the crews of both ships, and ordered them to release the sailors into Iranian custody. One of the ships ultimately complied with the request, while another did not. Nonetheless, Iranian state media attempted to claim that it was holding both crews, until it was confirmed that the US Navy had taken responsibility for 21 of the 44 individuals who’d abandoned their ships. The remaining 23 were held by Iran for two full days before being released to Dubai.

Prior to the incident involving the Riah, the IRGC apparently attempted to subject at least one other crew to similar treatment. On July 11, three fast-attack boats surrounded a British commercial vessel and attempted to block its course of travel through the Strait of Hormuz, but withdrew after being warned off by a nearby warship, the HMS Montrose. The memory of this incident will almost certainly inform British decision-making as it regards potential contribution to the US-led coalition that may form in the area of the Persian Gulf in the coming days and weeks.

Meanwhile, global perceptions of that coalition’s necessity will no doubt be influenced by the prospects for, and nature of, any resolution concerning the MT Riah, as well as whether or not similar incidents follow this first, unexplained seizure.