World leaders either become known for quickly learning life’s lessons–or not. The latter category is largely a product of one’s personal lust for power intertwined with an ideology allowing it to flourish. But membership is at times encouraged by the former’s failure to appropriately discourage the latter’s aggressive behavior early on.Falling into the latter category is Iran’s mullahs. It has taken them nearly a half century to learn an important lesson, coming after testing two U.S. presidents—one weak, one strong—who served in two different centuries. That lesson employs a simple rule of thumb concerning who has a foreign policy backbone:...