Secretary of State Rex Tillerson, U.S. Sen. Bob Corker (R-TN) and Defense Secretary James Mattis on Capitol Hill on October 30. (Keith Lane/Getty Images)
Secretary of Defense Jim Mattis and South Korean Defense Minister Song Young-Moo visit the DMZ between North and South Korea on October 27. (Jung Yeon-Je/AFP/Getty Images)
Defense Secretary James Mattis and Chairman of the Joint Chiefs Gen. Joseph Dunford make a statement on North Korea September 3. (Chris Kleponis - Pool/Getty Images)