To hear regime officials tell it, the seizure was fully justified – a simple enforcement of the country's sovereign rights under international law. But there's ample reason to believe that, contrary to Tehran's claims, the British ships were not in fact encroaching on Iranian territorial waters, and the move was instead intended as a political signal to London and other Western capitals.
The episode follows a now-familiar pattern. Iran's strategic position atop the Strait of Hormuz, a vital global waterway through which a fifth of world oil passes, is a key asset for Tehran – and a serious worry for regional oil suppliers and foreign oil consumers alike.
In response to expanding U.S. sanctions, the Iranian regime has taken on a more and more aggressive role in the waterway in recent weeks. By doing so, Tehran is seeking to deter further Western pressure, and signaling to America and its allies that further sanctions could carry potentially dire global consequences.
Nor is Tehran's choice of victims all that surprising. In the midst of the second Iraq War a dozen years ago, the Iranian regime did something remarkably similar when it apprehended a British naval vessel, the HMS Cornwall, and temporarily held its fifteen-member crew hostage. London's feeble response at the time provided Tehran with a clear political win, allowing Iranian leaders to frame the sailors' eventual release as "a gift" to the UK. It also confirmed to Iran's rulers that the U.S. and its allies – then preoccupied with the protracted conflict in Iraq – simply weren't prepared for a serious confrontation with the Islamic Republic.
In carrying out their latest act of aggression, Iran's leaders were clearly betting that Britain, at least, is no readier now. Yet Iran's maritime moves could end up being a major miscalculation, for several reasons.
First, London retains a great deal of potential leverage by which to pressure – and, if necessary, to punish – Tehran. To be sure, the British government has stressed that it seeks a diplomatic solution to the unfolding crisis, and has forwarded the issue to the United Nations Security Council in search of a multilateral solution. But Whitehall has also signaled that it is prepared to unilaterally enact sanctions against Iran, including potentially freezing the assets of key regime officials and actors.
That, in turn, would further diminish Europe's already-declining trade with the Islamic Republic. It would also likely lessen Britain's previous support for the EU's preferred method to continue commerce with Iran, formally known as the Instrument in Support of Trade Exchanges, or INSTEX.
Second, the seizure could prompt the UK to take on a much more hands-on role in regional security.
Up until now, the British government has stopped short of endorsing the Trump administration's efforts to internationalize security in the Hormuz Strait, worried that doing so might further inflame regional tensions. But in the wake of last week's interdiction, British officials have indicated that their government is prepared to act more assertively to preserve freedom of navigation in the and around the Persian Gulf. That, in turn, could turn London into a potential partner in the Trump administration's plans for a military coalition of nations to collectively protect maritime traffic in the Strait.
Most of all, however, Britain's hardening stance vis-à-vis Iran has the potential to seriously fracture the European consensus over the Islamic Republic.
By and large, European nations have opposed the Trump administration's campaign of "maximum pressure" against Iran, and sought to continue to do business with the Iranian regime. More and more, however, these same nations are drifting reluctantly toward the realization that Iran isn't a trustworthy economic or political partner. England's recent experience only serves to confirm those conclusions, while London's leadership role in European politics means that London's decisions will carry significant weight with the EU.
Tehran's recent maritime interdiction, therefore, might turn out to have been a serious miscalculation, rather than the strategic success that its leaders had hoped.
Ilan Berman is Senior Vice President at the American Foreign Policy Council.