Faced with the prospect of continuing Israeli airstrikes and further American involvement, Iran’s parliament has reportedly approved plans to close the strait of Hormuz.
This is potentially a very dangerous moment. The strait of Hormuz is an important shipping lane through which 20% of the world’s oil transits – about 20 million barrels each day.
The waterway connects the Persian Gulf and the Gulf of Oman. Iran can either disrupt maritime traffic or attempt to “close” the strait altogether. These are distinctly different approaches with different risks and outcomes.
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The first option is to try and disrupt maritime traffic like Yemen’s Houthi rebels have been doing in the Red Sea since winter 2024. This can be done by attacking passing ships with rockets and drones.
There are already reports that Iran has started to jam GPS signals in the strait, which has the potential to severely interfere with passing ships, according to US-based maritime analyst Windward.
Disruption of this kind is likely to deter shipping companies from using this route for fear of casualties and loss of cargo. Shipping companies that want to avoid the Red Sea can always use alternative shipping lanes, such as the Cape of Good Hope route. As inconvenient as that is, there is no such option in the case of the Gulf.
As we’ve seen with Houthis’ attacks, such disruptions have impacts on oil price, but also ripple effects on stock markets and inflation. Although the US and its western allies can absorb these economic effects – certainly for a while – disrupting the strait would still demonstrate that Tehran has some leverage.
The credibility factor
The second option – “closing” the strait would involve interdicting all maritime traffic. This is akin to a blockade. And for it to work, as we have seen in the Black Sea with Russia’s failed attempt at blockading Ukraine, a blockade must be credible enough to deter all traffic.
Iran has a number of ways to block the strait. It could deploy mines in the waters around the choke point and sink vessels to create obstacles. Iran would also likely use its navy, including submarines, to engage those attempting to break the blockade; use electronic and cyber attacks to disrupt navigation; and threaten civilian traffic and regional ports and oil infrastructure with drones and rockets.
It’s worth noting that Iran still has plenty of short-range rockets. Israel claims to have destroyed much of its longer range ballistic-missile capability, but it is understood that the country still has a stockpile of short-range missiles that could be effective in targeting ships and infrastructure in the Gulf as well as US bases in the region.
Recent events have shown up Iran as a bit of a paper tiger. It has made bold claims about its plan to retaliate and the military strength it has to do so. Yet with almost no air power capabilities (apart from drones and missiles) and limited naval power – and with its proxies either defeated or on the back foot – Iran is no longer in a position to project power in the region.
Iran’s response to the current Israeli attacks have not managed to inflict any major damage or achieve any strategic or political objectives. It’s hard to see a change on the battlefield as things stand.
w:en:Kleptosquirrel/Wikimedia Commons, CC BY-SA
For this reason, Tehran’s best option is to target the strait of Hormuz, which has the potential to cause a significant spike in oil prices, leading to a major disruption of the global economy.
Short of being able to rival the US or Israel on the battlefield, Iran might decide to use asymmetrical means of disruption (in particular missile and drone attacks on civilian shipping) to affect the global economy. Closing or disrupting the strait would be an effective way of doing that.
A blockade, even a partial one, would offer Tehran some options on the diplomatic scene. For instance, it has been reported that the US asked China to convince Iran not to close the strait. This demonstrates that Tehran can use the threat of a blockade to its advantage on the diplomatic front. But for this to work, the blockade needs to be effective and thus sustained.
What would be the effect of a blocking the Strait?
Disrupting traffic in the strait could drag Gulf states – Iraq, Kuwait, Saudi Arabia, UAE, Bahrain and Qatar – into the conflict, since their interests will be directly affected. It’s important to consider how they might respond and whether this will drive them closer to the US – and even Israel, as was already happening with the Abraham Accords and the tentative, but shaky, rapprochement between Saudi Arabia and Israel.
These are all things Iran would have factored into its calculations a year ago when Israel was targeting its proxies, including Hezollah, Hamas and the various Shia militias it funds in Iraq and elsewhere. But now, given that it has suffered an enormous military setback, which has hurt the regime’s prestige and credibility – including, importantly, at home – Tehran is more likely to downplay these risks. I would expect it to proceed with its blockade plans.
Even if China voices concerns, like it did regarding the Houthis’ attacks, this is unlikely to change the decision. The regime is cornered. If the leaders believe they could be toppled, they are likely to consider the risks worth taking, particularly if they feel it could give them diplomatic leverage.
The US has enough naval and air power to disrupt such a blockade. It can preemptively destroy Iran’s mine-laying forces. It can also target missile launch sites inland and respond to threats as and when they arise.
This is likely to prevent Iran from completely closing the strait. But it won’t prevent the Islamic republic from disrupting maritime trade enough to have serious effects on the world economy. This might well be one of the last cards the regime has to play, both on the battlefield and in the diplomatic arena.
Basil Germond, Professor of International Security, Department of Politics, Philosophy and Religion, Lancaster University
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