On: Houthi advance boosts Iran’s leverage over the US and Saudi Arabia - but may...

A strait has changed hands, and three nations shudder. Twenty miles of water is now worth more than any army in the region.

Narrow ground multiplies the small. A few thousand men with boats now tax the commerce of the world, and the world’s navies learn that a fleet cannot besiege a coastline. The hammer is useless against water.

Iran has found the cheapest weapon ever forged: another man’s grievance. Tehran spends patience, and patience never requires resupply. Every ship slowed in that passage is leverage earned at Yemeni prices, not Persian ones.

But mark the emptiness. They face the sea, and their backs are turned to their own countrymen; a civil war paused is not a civil war ended. Legitimacy is terrain too, and theirs erodes with every shell fired seaward.

Here is the deeper flaw: their lifeline runs through the waters they have made a battlefield. The supply that feeds them crosses the very strait they now threaten to close. A hand on an enemy’s windpipe is well placed - until someone remembers to cut the arm.

And the great powers, so long divided, now share one conviction. A small actor who unites its enemies has won a battle and arranged its own siege.

I say it plainly: taking the strait was a mistake. The strait must be fought for daily; the loyalty of the people behind you is lost the day you stop noticing them. Whoever holds a pass and loses the province behind it holds a corridor to nowhere.

Watch the sea, then. But watch more closely the roads inland.