Why is the Strait of Hormuz so important, and can Iran really close it?

The Strait of Hormuz is about 33 kilometres wide at its narrowest, but the actual shipping lanes are only a few kilometres across. Every tanker leaving Saudi Arabia's Gulf coast, Kuwait, Iraq, Qatar, the UAE, and Iran itself has to pass through it. That is roughly a fifth of global oil and a big share of the world's LNG.

Can Iran close it? Not permanently, and not in the sense of a physical barrier. What Iran can do is make it dangerous enough that insurers refuse cover and shipowners refuse to sail. Mines are the cheapest way to do that, which is why the US has spent so much effort clearing them and striking the launchers used to lay them. Anti-ship missiles and fast-boat swarms are the other tools.

The catch for Iran is that its own exports go through the same strait. Closing it hurts Tehran as much as anyone. That is why Iranian diplomats keep saying they do not want to block it even as mines keep appearing. The mines are leverage, not a blockade.

For India, the relevance is direct. A large share of our crude comes through that water, and a large share of the crews on those ships are Indian. Even a partial disruption shows up in fuel prices and in worried families back home.