Commentary: Hormuz is no longer one front in US-Iran war - it is becoming a test

Commentary

The strategic waterway is becoming the clearest test of whether any state can use force to rewrite the rules governing freedom of navigation, says defence professor and navy veteran Jennifer Parker.

18 Jul 2026 06:00AM

CANBERRA: United States President Donald Trump’s proposal to charge a 20 per cent fee on cargo moving through the Strait of Hormuz under US protection was quickly walked back within a day. But it revealed how much the war is shifting.

More than 130 days into the conflict, what started as an effort to curb Iran’s nuclear ambitions is, at its core, becoming a fight over freedom of navigation.

Iran’s continued attacks on commercial shipping, despite the economic incentives contained in the June memorandum of understanding (MOU), show that Tehran is serious about using control of the Strait of Hormuz as leverage.

The US must adapt its strategy in response, but the threat to charge a toll was fundamentally in the wrong direction.

CHANGING THE RULES OF THE STRAIT OF HORMUZ

Iran has a history of attacking and interfering with shipping, from the Tanker War during its conflict with Iraq in the 1980s to attacks on six civilian vessels in and around the Gulf of Oman in 2019, and many other incidents of interference.

When Iran wants to send a strategic message, it attacks shipping.

In this context, it was not surprising that Iran responded to the first attacks by the US and Israel on Feb 28 by targeting civilian ships across the Gulf of Oman, Persian Gulf and Strait of Hormuz.

But Iran’s broader intention is to permanently change the navigation regime in the Strait by establishing the Persian Gulf Strait Authority, creating a new route into and out of the Gulf, and charging tolls for safe passage.

Even so, many assumed these measures would apply only during the conflict and that economic incentives would persuade Tehran to allow ships to transit safely again, like it did before the war.

A CRUCIAL TEST

The Strait of Hormuz is becoming the clearest test of whether freedom of navigation remains an enforceable international principle.

Around 80 per cent of international trade in goods by volume is carried by sea, and more than 99 per cent of international data traffic passes through cables on the seabed. Both depend on an open and predictable maritime order.

Freedom of navigation, protected under the 1982 United Nations Convention on the Law of the Sea (UNCLOS), is increasingly under pressure, from Houthi attacks on shipping in the Red Sea beginning in 2023 to China’s actions in the South China Sea. Specifically, UNCLOS protects the right of transit passage through “straits used for international navigation” which cannot be impeded or suspended.

For Asian economies that depend on trade, the outcome of Iran’s actions will affect not only energy security and shipping costs, but also the rules governing other contested waterways.

WASHINGTON’S FAILED BET

Washington initially tried to restore passage through the strait by economic pressure, via a naval blockade of Iranian ports then economic incentives. Neither proved enough.

During the April ceasefire, the US did not respond every time Iran attacked or interfered with shipping. In fact, the ceasefire enacted on Apr 8 was predicated on Iran reopening the strait. That did not happen, yet the US for the most part maintained the ceasefire.

When the Jun 17 MOU was signed, the US appeared to believe that significant economic incentives would be the decisive factor.

Point 5 of the MOU states that Iran would use its “best efforts for the safe passage of commercial vessels with no charge for 60 days” but also leaves the “future administration and maritime services” to further dialogue and discussion, ”in line with” international law.

Tolls are not consistent with international maritime law.  But, unfortunately, this section of the MOU was very ambiguous, leaving both sides to make varied interpretations.

The latest Iranian attacks on commercial ships on Jul 6 and Jul 7 showed that economic incentives in the MOU would not be enough for Tehran to give up its key source of negotiating leverage. Three ships were attacked, including a Qatari liquefied natural gas tanker struck very close to the Omani coast while allegedly using an alternative route to get around the one authorised by Iran.

THE GREATER CHALLENGE

The challenge for the US is that if it allows Iran to impede shipping through attacks, Tehran’s control could become permanent, with broad implications for freedom of navigation.

Understood in this context, it is easy to see why the US responded to Iran’s attacks on three ships transiting in and around the strait by striking Iran.

The US calculates that freedom of navigation is critical, and if economic incentives didn’t work, deterrence by punishment may.  But the conflict has demonstrated that bombing alone is unlikely to restore safe passage through the Strait.

As the conflict becomes a battle over freedom of navigation, it exposes a gap in the US strategy and shows how earlier missteps are coming back to undermine it.

When Mr Trump said on Monday (Jul 13) that he would impose a charge on cargo vessels transiting the Strait, it was at odds with the principle the US is seeking to defend. Despite a quick U-turn, a US president suggesting that the principle of freedom of navigation is easily abandoned weakens the broader argument.

The greater challenge is that the US approach to the war has left allies and partners unwilling to send assets to help protect navigation in the region, as a number did during the Tanker War. To secure that support, Washington must frame the next phase around protecting commercial shipping, rather than the broader conduct of the war.

The US cannot defend freedom of navigation alone, or only when convenient. It must rebuild international support and make clear that no state can use force to control a global waterway.

What happens in Hormuz will shape not only this conflict, but the future security of maritime trade.

Jennifer Parker is an Adjunct Professor with the University of Western Australia Defence and Security Institute and a Non-Resident Fellow at the Lowy Institute. She served for more than 20 years as a warfare officer in the Royal Australian Navy.

Source: CNA/zw(ch)