In 1815, with Commodore Stephen Decatur’s guns trained on his harbor, the Dey of Algiers signed a treaty with the United States, then told the Americans what he thought of it: My power has been wrested from my hands. Draw the treaty at your pleasure, and I will sign it. But beware the moment I recover my power — for with that moment, your treaty shall be waste paper.

No adversary has explained himself more honestly, and no lesson from America’s first war has been more expensively relearned: an agreement is a snapshot of a power relationship, not a substitute for one. It binds exactly as long as the leverage that produced it. We are relearning it now with Iran, and we have seen this movie before — in fact, we premiered it.