A raging conflict threatening to further splinter Yemen is also casting a shadow over a crucial Arab alliance that has backed Donald Trump’s policy against Iran. But the escalating showdown between Trump and Iran has prompted the U.A.E. to rethink its priorities to avoid a conflict that could have a devastating impact on its economy. “There have always been differences between the Emiratis and the Saudis,” said James Dorsey, senior fellow at RSIS. He added, “Those differences have become more evident with the U.A.E.’s partial withdrawal from Yemen.”