Patrick Shanahan

(FOX NEWS) -- Defense Secretary James Mattis will be leaving his post on January 1, weeks ahead of his initially announced exit of February.

President Trump announced the news in a tweet Sunday morning, writing: "I am pleased to announce that our very talented Deputy Secretary of Defense, Patrick Shanahan, will assume the title of Acting Secretary of Defense starting January 1, 2019. Patrick has a long list of accomplishments while serving as Deputy, & previously Boeing. He will be great!"

This story will be updated.

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