Syria, Mattis, Afghanistan, shutdown: Donald Trump ends year in chaos

To top it all off, US share prices tumbled as investors worried about the looming shutdown, slower economic growth and the Federal Reserve's projections for more interest rate hikes next year.

U.S. President Donald Trump arrives for a signing ceremony for H.R. 2, the “Agriculture Improvement Act of 2018” in Washington. (Reuters)

Trump’s presidency has lurched from crisis to crisis since he took office less than two years ago, but Thursday was a landmark day of chaos that appeared to test the resolve of even senior Republican backers in Washington.

Defense Secretary James Mattis, a widely respected figure seen as a stabilizing influence inside the administration, handed in his resignation after arguing with Trump over foreign policy in a White House meeting.

Mattis then released a letter that showed fundamental policy differences between the two men and implicitly criticized Trump’s disregard for allies abroad. Also on Thursday, Trump resisted pressure to stand down from a decision to withdraw U.S. troops from Syria, made plans to pull American forces out of Afghanistan and pushed the U.S. government toward a shutdown over funding for a border wall.

To top it all off, U.S. share prices tumbled as investors worried the looming shutdown, slower economic growth and the Federal Reserve’s projections for more interest rate hikes next year.