I've been through the Strait of Hormuz many times. Here's my take

Telegraph

3 days ago

Obtaining accurate Battle Damage Assessment after a raid or strike is rarely quick. What effect you have had is sometimes hard to see and what knock-on effect you have had, hard to judge.
Following Operation Midnight Hammer and the US penetration strikes on Iran's nuclear programme, one place likely to see knock-on effects is the Strait of Hormuz. Those of us who have faced down onrushing swarms of fast-attack craft there, or been involved in planning how to counter them – or the Iranian mines or submarines – will know how important the Strait is to Iran. Much effort and expense has been devoted to ensuring that they could control it if the moment arose. Is this the moment?
Yesterday afternoon the Iranian parliament officially approved closing the Strait for the first time since 1972. While that is a nominal authorisation rather than a decision, it affirms the Iranian belief that control of this key chokepoint is in their gift.
One point that needs to be made loud and clear is the difference between closing the Strait and contesting it. They could close it in spite of the fact that the skies appear to belong to the Israeli air force. The Strait is a long sortie for Israeli planes and will not have been a priority in the last few weeks. Iran has thousands of mines and fast attack craft, dispersed along the coast specifically to make them hard to strike. They have hard-to-detect midget submarines armed with heavyweight torpedoes designed to sink the largest ships. They also have an array of shorter-range cruise and ballistic missiles on mobile launchers which could cause havoc if all deployed at once: think Houthis x 10. We now know these capabilities are not as good as we thought, and some will have been neutralised, but mass and mobility still count.
But I don't believe they will close the Strait, not deliberately anyway. It's not in their economic interest, would annoy what few regional friends they have – in particular Qatar – would unite the Gulf against them and, most critically, a closure would be unacceptable to China. The tried and tested assumption has always been Iran would only close the Strait if the regime was about to fall, and we don't seem to be there yet.
Iran might contest the chokepoint, though. This is a different proposition and is being confused in the dialogue a lot. GPS jamming there is already at record high levels, though this is probably not aimed at merchant shipping: it will be intended to confuse US and Israeli aircraft and missiles. Boardings, riding off and harassment have been standard fare for the last 20 years – they could turn this up a notch, targeting specific carriers and cargoes – perhaps those destined for Western nations only.
Mines are key here because you don't even need to lay them to have an effect, just say you have, and risk appetites and war risk insurance premiums adjust accordingly. They already are, and some ships are already refusing to go through. The Iranian Revolutionary Guard Corps Navy (which is separate from the regular Iranian navy) have a tactic where a swarm attack drives your ship into a pre laid mine pattern. This would be too aggressive (for now) but the point to note is that they have procured for, practiced and rehearsed this sort of thing since the late 80s. It's a different battlespace to the one that took dozens of allied warships to keep open back then.
Until quite recently the Royal Navy was one of the best in the world at mine countermeasures (MCM) – it's one of the US Navy's few weaknesses – and again until recently we had a useful MCM force of several minehunters and a command ship based in the Gulf at Bahrain. But a fatal combination of a manpower crisis in the Royal Fleet Auxiliary, an unfortunate collision, maintenance cycles and a rushed plan to switch from manned minehunters to unmanned systems means that right now there is just one RN minehunter active in the Gulf, and there is no option to deploy the new unmanned stuff. Making a useful MCM effort in the Strait could be difficult in the teeth of Iranian missiles anyway, though if we had the assets the US could probably assign Aegis air-defence warships to protect them. It would also be complicated by the fact that Iran sometimes uses free-floating unmoored mines, illegal under the Hague Convention, which can drift into an area you think you've cleared.
While the Bab el Mandeb has one significant difference to Hormuz – there is an alternative route – the way the Houthis conducted escalation management there is relevant. For over a year they created just the right amount of risk to achieve their end states without provoking a massive response. In the end they got one anyway, and took such a battering from America that they ceased fire (though reportedly they have now ended that) but that was as much to do with the change in US leadership as anything else. The point is, for a long time, they didn't close the Bab El Mandeb but they did control it, and who do you think they learned that skill from?
So I do think that Iranian disruption activity in the Strait is likely. Their leadership is clearly in disarray. Command and control is shot and their competence and authority eroded with every unopposed Israeli jet flying over Tehran. Add some strategic strikes that you never saw coming and there must be some desperate conversations going on underground just now. The regime needs to do something visible.
Nevertheless, if they do interfere there in some form or other, they know full well what the response will be because there are two US carrier strike groups in the Gulf of Oman. A third, the USS Gerald R Ford, sails for the Mediterranean tomorrow. The beating the Houthis eventually received is there to serve as an object lesson. But if they ignore this and contest the strait anyway, operations to keep it clear it will be difficult, high risk, lengthy (mine clearance is a notoriously protracted operation), expensive in munitions (striking minelaying fishing boats and jet skis with missiles) and most importantly, embroil the US in the exact conflict they've just said they want to avoid. And the Houthis are down but probably not out of this either. That said it would be a sea and air fight, no messy ground war 'among the people' as in Iraq and Afghanistan, and it would be expensive in money but probably not in US and allied lives.
I can't be sure how this plays out any more than I know how damaged Iran's ability to make a nuclear weapon is today, and would treat with caution anyone professing to know either. Asking around, it's perhaps interesting that people like me who have seen Iran's capabilities up close over the years tend to think that limited disruption in the Strait is now inevitable; it's in their DNA, they are well prepared and it's hard to counter. But those who haven't, and look at the situation from a more diplomatic or economic angle, tend to think it isn't. I hope they're right because the last thing anyone needs right now is another spike in oil and gas prices.
The question for me, today, is does Iran care?