Last Thursday, Secretary of Defense James Mattis submitted his letter of resignation. In the letter, Mattis stated that he would stay in his role for three more months in order to maintain order and provide a smooth transition.

“One core belief I have always held is that our strength as a nation is inextricably linked to the strength of our unique and comprehensive system of alliances and partnerships,” Mattis said.

While Mattis has been transparent about his views, so has the president. Two days ago, Trump released a string of tweets; one in particular shows the contradicting viewpoints the two men share.

“When President Obama ingloriously fired Jim Mattis, I gave him a second chance,” Trump said. “Some thought I shouldn’t, I thought I should. Interesting relationship-but I also gave all of the resources that he never really had. Allies are very important-but not when they take advantage of U.S.”

The contents of the letter have not gone unnoticed by the press, with Mattis highlighting that there were several issues on which he and the president did not agree on, including the removal of troops from Afghanistan and Syria.

“Because you have the right to a Secretary of Defense whose views are better aligned with yours on these and other subjects, I believe that it is right for me to step down from my position,” Mattis said.

Over the weekend, however, President Donald Trump announced that Mattis would be replaced on Jan. 1 by the Deputy Secretary of Defense, Patrick Shanahan. This shift disables Mattis from shaping or impacting national security through his original leave date cited to be at the end of February.

“I am pleased to announce that our very talented Deputy Secretary of Defense, Patrick Shanahan, will assume the title of Acting Secretary of Defense starting Jan. 1,” Trump said. “Patrick has a long list of accomplishments while serving as Deputy, and previously Boeing. He will be great!”