Arrival: Alex Azar was nominated by President Trump to replace outgoing Health and Human Services Secretary Tom Price in late 2017. Azar was confirmed by the Senate Jan. 24, 2018, in a 55 to 43 vote and took office Jan. 29, 2018. (Jacquelyn Martin/AP)
Departure: After a year of foreign policy tensions with the president, Secretary of State Rex Tillerson was fired March 13, 2018. Trump talked of replacing Tillerson with then-CIA Director Mike Pompeo for months prior to his actual firing. (Evan Vucci/AP)
Departure:Trump fired Department of Veterans Affairs Secretary David Shulkin March 28, 2018, after weeks of speculation that the president was looking to get rid of him. A February Inspector General report criticized Shulkin for wasteful and unethical actions, though Shulkin accused the White House and VA subordinates of trying to undermine him because of policy battles. (Andrew Harnik/AP)
Shuffle: Trump nominated then-CIA Director Mike Pompeo to replace Rex Tillerson as secretary of state on the same day that Tillerson was fired. Pompeo was confirmed by the Senate April 26, 2018, by a 57 to 42 vote and took office the same day. (Manuel Balce Ceneta/AP)
Arrival: Formerly the deputy director of the CIA, Gina Haspel was nominated to formally lead the agency by Trump March 13, 2018. She was confirmed by the Senate May 17, 2018, in a 54 to 45 vote, and took office the same day. (Pablo Martinez Monsivais/AP)
Departure: After a series of scandals involving housing payments, expenses and hiring practices, Environmental Protection Agency Administrator Scott Puritt was under multiple investigations by agency watchdogs and Congress and ultimately chose to resign July 5, 2018. (Brendan Smialowski/AFP/Getty Images)
Arrival: After a false start nominating White House Doctor Ronny Jackson to lead the Department of Veterans Affairs, Trump chose then-Under Secretary of Defense for Personnel and Readiness Robert Wilkie to lead the VA. Wilkie was confirmed July 23, 2018, in an 86 to 9 vote and took up the position July 30. (Andrew Harnik/AP)
Departure: After controversy over his decision to recuse himself from the special counsel's Russia investigation, Attorney General Jeff Sessions offered his resignation at President Donald Trump's request Nov 7, 2018. (Pablo Martinez Monsivais/AP)
Arrival: Trump controversially chose former U.S. Attorney Matt Whitaker as the new U.S. acting attorney general Nov, 7, 2018. His appointment has been challenged in court as Trump having sidestepped the Constitution by naming Whitaker to the position in place of Deputy Attorney General Rod Rosenstein. (Charlie Neibergall/AP)
Departure: Trump announced Oct. 9, 2018, that U.S. Ambassador to the United Nations Nikki Haley would be leaving her position at the end of the year. At the time of her resignation, Trump praised Haley as a "fantastic person." (Evan Vucci/AP)
Departure: After just over a year on the job, Chief of Staff John Kelly will also leave the Trump administration by the end of the year, the president announced Dec. 8, 2018. The two reportedly faced tensions throughout Kelly's tenure. (Susan Walsh/AP)
Departure: Trump announced Dec. 15, 2018, that Ryan Zinke (right) would be leaving as the Department of Interior secretary by the end of the year. Zinke was plagued by accusations and investigations into his travel practices and business deals while leading the agency. (Scott Keeler/Tampa Bay Times via AP)
Shuffle: Though already director of the Office of Management and Budget, Mick Mulvaney was named acting chief of staff by Trump on Dec. 14, 2018. He will take over the position after John Kelly's departure. (Alex Brandon/AP)
Departure: Defense Secretary Jim Mattis handed in his resignation Dec. 20, 2018, shortly after the president announced his intent to withdraw U.S. troops from Syria. Though Mattis was initially supposed to stay on until February 2019, Trump announced days after his resignation that he would be removing Mattis two months early and replacing him with Deputy Secretary of Defense Patrick Shanahan. (Pablo Martinez Monsivais/AP)