The White House is preparing for what could become a multi-day or even multi-week exchange of fire with Iran over the Strait of Hormuz. The length and severity of the new campaign hinge entirely on Tehran's next moves, U.S. officials tell Axios. Why it matters: A war that began with the goal of degrading Iran's missile capabilities and destroying what remained of its nuclear program has evolved into an open-ended fight over the world's most important energy chokepoint. A U.S. official said th