Mr Donald Trump is a deceptively conventional US president of the 21st century. Elected to unpick his nation's entanglements in the Middle East, he has served to deepen and extend them. What most separates him from his immediate predecessors is his lack of an alibi.
Former president George W. Bush had terrorist atrocities to avenge, even if he avenged them with a fiasco or two. As for Mr Barack Obama, the Arab Spring dawned and then darkened over the course of his tenure. It required an answer.