Trump’s foreign policy decision on Syria, which he had promised back on the campaign trail in 2016, was reportedly the final straw for Mattis. His decision to resign was based on principle, sources told Fox News at the time.
"Because you have the right to have a Secretary of Defense whose views are better aligned with yours on these and other subjects, I believe it is right for me to step down from my position," Mattis wrote at the time.
Meanwhile, Bolton was left to try to smooth over backlash in Washington and abroad over Trump’s policy decision on Syria.
Bolton and other officials in the White House worked “behind the scenes” to slow the president’s order to pull all 2,000 troops from Syria, with Bolton pushing for the U.S. departure from Syria to include the condition that Turkey guaranteed it would not target Kurdish fighters.
Turkish President Recep Tayyip Erdogan accused Bolton of making a “serious mistake” in complicating Trump’s Syria withdrawal — and Bolton would ultimately also exit his post after being fired by Trump in September.
In announcing Bolton’s termination, Trump said he “disagreed strongly with many of his suggestions.”