Risks growing as diplomatic efforts remain stalled and Iran threatens unrestrained retaliation DUBAI—America’s Gulf allies are steeling themselves for a heavy U.S. bombardment of Iran that they expect to trigger a vicious cycle of retaliation against their own economic and civilian infrastructure as early as this week.The Trump administration and Arab mediators are making a number of efforts to reach a negotiated end to the conflict. But the lack of progress paired with U.S. and Iranian threats of especially ferocious fighting if the conflict resurges are heightening concerns across the region.President Trump has been leaning toward a large postelection attack...