“As acting secretary of defense, I now look forward to working with President Trump to carry out his vision alongside strong leaders including the service secretaries, the Joint Chiefs of Staff, the combatant commanders, and senior personnel in the Office of the Secretary of Defense.”

On Dec. 20, a day after Trump abruptly called for the withdrawal of US troops from Syria, Mattis announced he would step down – writing a two-page letter of resignation in which he rebuked the president’s defense and foreign policies.
Patrick M. Shanahan becomes the acting United States secretary of defense following the resignation of Jim Mattis.