The ongoing showdown with Iran is one of the greatest US foreign policy challenges of this century. Iran's ambition to become the region's superpower has been bolstered by its large oil and gas supply, Shiites gaining control in Iraq, Hezbollah—an Iranian proxy army—fighting Israel to a standstill, and, its defiant move to become a nuclear power. Bold messages from Iran, such as that it will retaliate against the West and its allies if they try to impede its rise to power, are challenging to interpret.