LONDON—With the United States and Iran agreeing to a two-week ceasefire, many are using this pause to wonder what, if anything, would allow US President Donald Trump to declare victory and end the fighting. One necessary condition, it seems, is the permanent reopening of the Strait of Hormuz, through which around one-fifth of the global oil supply flows. But even with the ceasefire temporarily reopening the Strait, Trump has not secured lasting stability for shipping. Of course, had Trump simply refrained from attacking Iran in the first place, the Strait never would have been closed.

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