Ben Carson's remarks on foreign policy have repeatedly raised questions about his grasp of the subject, but never more seriously than in the past week, when he wrongly asserted that China had intervened militarily in Syria and then failed, on national television, to name the countries he would call on to form a coalition to fight the Islamic State. Faced with increasing scrutiny about whether Carson -- who leads in some Republican presidential polls -- was capable of leading US foreign policy, two of his top advisers said in interviews with The New York Times that he had struggled to...