President Donald Trump announced in a series of tweets on Sunday that Deputy Defense Secretary Patrick Shanahan will replace current Defense Secretary Jim Mattis following Mattis' resignation.
President Trump also tweeted Mattis will leave Jan. 1 — two months ahead of schedule.
Mattis told the president he'd leave Feb. 28, which would have let him attend an upcoming NATO defense meeting and ensure the Pentagon's policies are "properly articulated and protected."
Mattis announced his resignation a day after President Trump announced he'd withdraw American troops from Syria. In his resignation letter, Mattis said the president had the right to a secretary "whose views are better aligned with" Trump's.