The threat to close the Strait of Hormuz is the oldest line in Iranian deterrence. It has been recited since the Iran-Iraq War, repackaged after every sanctions tightening, and trotted out reflexively whenever a US carrier strike group enters the Gulf. The line works because the audience accepts the premise: that Iran could close the Strait if it wanted to. The premise is half true. Iran has the capability to disrupt traffic for days, possibly weeks. What it does not have is the capability to survive doing so.