According to CBS News, Defense Secretary James Mattis will resign at the end of February, he informed President Trump in a letter Thursday. The defense secretary said he is stepping down because of the differences in viewpoints with the president.

“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. 

President Trump announced the news in a tweet and praised Mattis’ tenure as secretary. 

“During Jim’s tenure, tremendous progress has been made, especially with respect to the purchase of new fighting equipment,” President Trump wrote on Twitter. “General Mattis was a great help to me in getting allies and other countries to pay their share of military obligations. A new Secretary of Defense will be named shortly. I greatly thank Jim for his service!”