The use of Shi’ite militias to try to take back the Iraqi city of Ramadi from Islamic State risks unleashing more sectarian bloodletting, current and former U.S. officials said, but Washington and Baghdad appear to have few other options. The prospect of Iranian-backed militias leading efforts to retake Ramadi underlines Washington’s dwindling options to defeat Islamic State in Iraq, with Prime Minister Haider al-Abadi’s grip on power weak, a national army still in its infancy and Tehran increasingly assertive. Islamic State’s capture of Ramadi, despite months of U.S.-led air strikes and military advice, marked a fresh low for the shattered Iraqi army, which beat a chaotic retreat from the city over the weekend. Abadi immediately turned to the Shi’ite militia groups, backed by Iran, which together have become the most powerful military force in Iraq since the national army first collapsed last June in the face of sweeping […]