Conflict in the Strait of Hormuz is spilling into the Indian Ocean

16 Mar 2026 11:38 AM

EXPERT COMMENT

The effective blockade of the strait during the US-Israeli war with Iran has increased the chance of accidents and forced ships into alternative routes with their own risks.

The US-Israeli war with Iran has turned the Indian Ocean into a theatre for major maritime confrontations. 

On 2 March, in response to US-Israeli strikes, Iran announced it was closing the Strait of Hormuz, the vital maritime chokepoint that connects Gulf waters and the wider Indian Ocean beyond. On 4 March, a US submarine sunk the Iranian frigate IRIS Dena off the coast of Sri Lanka. Since the outbreak of the conflict, at least 18 vessels have been attacked in Gulf waters.  

The US now claims Iran’s navy is destroyed. Despite this, the Strait of Hormuz remains functionally closed. 

While some analysts argue that Iran lacks the power to fully control the strait, Iran’s strategy does not depend on naval control. If Iran can launch missile or drone attacks from its coast, it can impose enough risk to disrupt shipping. The recent experience in the Red Sea illustrates this dynamic: a relatively small number of Houthi missile and drone attacks caused container traffic in the region to fall by roughly 90 per cent in 2024.

Iran’s ability to essentially close the strait will have a knock-on effect on wider maritime traffic, creating new security risks as ships seek alternative routes. While Iran has vowed to disrupt international trade to inflict pressure on US President Donald Trump, the US may seek to intercept ships bound for Iran, creating dangerous conditions for escalation in the increasingly crowded Indian Ocean and beyond.

Click here to continue reading the full version of this Expert Comment on the Chatham House website.