As President Donald Trump steps up efforts to engage North Korea in nuclear disarmament talks, the State Department is in the most turmoil since the president's inauguration.

The latest upheaval came Tuesday with the sudden firing of Secretary of State Rex Tillerson, who was dismissed with few details provided by the White House. Trump picked CIA Director Mike Pompeo to be the next secretary of State.

The moves followed Trump's abrupt announcement last week of a yet-to-be-arranged meeting with North Korean leader Kim Jong Un.