(FILES) This file photo taken on December 6, 2017 shows US President Donald Trump speaking alongside Secretary of Defense Jim Mattis (2nd R) as he holds a Cabinet Meeting in the Cabinet Room at the White House in Washington, DC.
US Defense Secretary Jim Mattis said December 15, 2017 he does not see the need for a stepped-up military posture against Iran, the day after a top diplomat said evidence shows Tehran is supporting Huthi rebels in Yemen.US ambassador to the United Nations Nikki Haley on Thursday presented missile fragments and other military gear that she said came from Iran and had been used against US ally Saudi Arabia.
 / AFP PHOTO / SAUL LOEB
Donald Trump at a cabinet meeting in the White House earlier this month. AFP / Saul Loeb

A national security strategy should provide clarity, but the Trump foreign policy doctrine is laced with contradiction