WASHINGTON (AP) — Defense Secretary Jim Mattis is stepping down from his post, President Donald Trump announced Thursday, after the retired Marine general clashed with the president over a troop drawdown in Syria and Trump’s go-it-alone stance in world affairs.

Mattis, perhaps the most respected foreign policy official in Trump’s administration, will leave by the end of February after two tumultuous years struggling to soften and moderate the president’s hardline and sometimes abruptly changing policies. The announcement came a day after Trump surprised U.S. allies and members of Congress by announcing the withdrawal of all U.S. troops from Syria, and as he continues to consider shrinking the American deployment in Afghanistan.

In his resignation letter, Mattis alluded to disagreements with Trump as the reason for his departure.

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