The war between the US, Israel and Iran is now entering its fourth week, and despite the loss of many senior figures, the Iranian regime survives.  

It is very difficult to bomb people into democracy. And so this war risks becoming a trial of strategic endurance. Can Iran keep the Strait of Hormuz closed long enough to weaken Washington’s will to fight?

The longer the Strait remains closed, the greater the pressure. Rising oil prices are fuelling inflation and with it, political opinion against the war. The bond market historically wields enormous power over US presidents; every day the war continues increases the cost of US borrowing.

The US military’s ability to fight at the current tempo will also be constrained if the Strait remains closed. As the Modern War Institute recently pointed out, 50 per cent of global seaborne sulphur passes through the Strait. Prices are up 25 per cent since the war began. Sulphur, a byproduct of crude oil production, is crucial to extracting copper from low-grade ore.

Copper and sulphur are used in almost every military platform imaginable, from motors to explosives to sensors, radars, avionics, guidance systems, and much more. For example, it will take over 30,000 kilograms of copper just to replace two US radar systems destroyed by Iran. If the Strait remains closed long enough, falling sulphur supplies could effectively curtail American combat power.

What this all proves is how crucial sea lanes are to the defence industrial base and the wider economy. This is a point certainly not lost here in Australia, where many commentators frequently warn of our reliance on sea lanes and the need to protect them.

As the argument goes, the nuclear submarines we are procuring under AUKUS will be vital to this, even if they eventually cost hundreds of billions of dollars.

Yet at the time of writing, the war is entering its fourth week and still the Strait remains effectively closed to shipping, despite overwhelming American naval dominance and the active participation of US nuclear-powered submarines in the conflict.

As Iran has proven, it does not take many low-cost drones or sea mines to hit a few tankers and effectively close one of the world’s most vital waterways. How many nuclear-powered submarines do you need to provide effective air defence against massed Shahed drones? How many do you need to defend against massed uncrewed surface vessels?

The answer, of course, is redundant. SSNs are not designed for those tasks. In any case, the decision to re-open the Strait will not be made by the US Navy, by Washington, or even Tehran. It will be made in the boardrooms of insurance companies in the City of London. Insurance premiums for ships transiting the Strait are currently up 300 per cent since the start of the war; even if ships can technically transit the Strait, the cost of doing so remains unsustainably high.

How many nuclear-powered submarines will it take to lower those premiums? How many SSNs do you need to change the mind of an actuary working for Lloyd’s of London?

The US currently operates around 53 SSNs and still the Strait of Hormuz remains closed (despite the vocal protests of Donald Trump and his demands for allied help). Australia intends to acquire eight.

Imagine a scenario whereby an adversary attempted to close maritime chokepoints vital to Australia using low-cost airborne or underwater drones, sea mines, or other asymmetric capabilities like those fielded by Iran in the Middle East.

If all the might of America’s SSN fleet cannot currently open the Strait of Hormuz from a relatively small power like Iran, can Australia’s future SSN fleet really keep our own sea lanes open against a peer adversary?

SSNs are undoubtedly a powerful platform. They have deterrent value. But their deterrence value and use case must be considered against the colossal cost of procuring them, especially for a middle power like Australia. Their deterrence value must also be considered against the enormous sacrifices that are already being made to the rest of the ADF.

As the war in the Middle East continues, Australian observers and military planners must look at our own military budget and ask themselves: how many nuclear submarines will it take to open the Strait of Hormuz?

Ewen leads the Australian Defence Magazine and is the founder of the strategic advisory firm Greyhaven Co.