Defense Secretary James Mattis letter of resignation
In a letter to the president dated Thursday, Mattis wrote about his beliefs in "treating allies with respect," and that the US "must be resolute and unambiguous" in how it approaches countries "whose strategic interests are increasingly in tension with ours," including China and Russia.
"We must do everything possible to advance an international order that is most conducive to our security, prosperity and values, and we are strengthened in this effort by the solidarity of our alliances," he wrote.
"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. He said his last day in office would be February, 28, 2019.
https://www.buzzfeednews.com/article/verabergengruen/defense-secretary-james-mattis-retire-trump
Letter here:
https://www.documentcloud.org/documents/5655960-Letter-From-Secretary-James-N-Mattis.html#document/p1
= new reply since forum marked as read
People who know him have been saying this on CNN and MSNBC for an hour. He was fired. People who know him said he is staying since he is worried about what would happen to the country if he left. 
