US Defense Secretary Jim Mattis quits day after Donald Trump announces Syria withdrawal, Read full text of letter here

US Defense Secretary Jim Mattis resigned on Thursday, a day after President Donald Trump shocked the US establishment by pulling out of Syria. In a letter to Trump, Mattis suggested his worldview, which favors traditional alliances and standing up to "malign actors," stands at odds with the president's. "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. Moments before the Pentagon released Mattis's letter, Trump tweeted that his defense secretary would be retiring "with distinction, at the end of February."

"During Jim's tenure, tremendous progress has been made, especially with respect to the purchase of new fighting equipment," Trump said. "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!"

General Jim Mattis will be retiring, with distinction, at the end of February, after having served my Administration as Secretary of Defense for the past two years. During Jim’s tenure, tremendous progress has been made, especially with respect to the purchase of new fighting....

— Donald J. Trump (@realDonaldTrump) December 20, 2018

Read More | 3 Indian-origin students in Time's 25 most influential teens of 2018

Read Jim Mattis’s Letter to Trump: Full Text

Dear Mr. President:

I have been privileged to serve as our country’s 26th Secretary of Defense which has allowed me to serve alongside our men and women of the Department in defense of our citizens and our ideals.

I am proud of the progress that has been made over the past two years on some of the key goals articulated in our National Defense Strategy: putting the Department on a more sound budgetary footing, improving readiness and lethality in our forces, and reforming the Department’s business practices for greater performance. Our troops continue to provide the capabilities needed to prevail in conflict and sustain strong U.S. global influence.

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. While the US remains the indispensable nation in the free world, we cannot protect our interests or serve that role effectively without maintaining strong alliances and showing respect to those allies. Like you, I have said from the beginning that the armed forces of the United States should not be the policeman of the world. Instead, we must use all tools of American power to provide for the common defense, including providing effective leadership to our alliances. NATO’s 29 democracies demonstrated that strength in their commitment to fighting alongside us following the 9-11 attack on America. The Defeat-ISIS coalition of 74 nations is further proof.

Similarly, I believe we must be resolute and unambiguous in our approach to those countries whose strategic interests are increasingly in tension with ours. It is clear that China and Russia, for example, want to shape a world consistent with their authoritarian model — gaining veto authority over other nations’ economic, diplomatic, and security decisions — to promote their own interests at the expense of their neighbors, America and our allies. That is why we must use all the tools of American power to provide for the common defense.

My views on treating allies with respect and also being clear-eyed about both malign actors and strategic competitors are strongly held and informed by over four decades of immersion in these issues. 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.

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. The end date for my tenure is February 28, 2019, a date that should allow sufficient time for a successor to be nominated and confirmed as well as to make sure the Department’s interests are properly articulated and protected at upcoming events to include Congressional posture hearings and the NATO Defense Ministerial meeting in February. Further, that a full transition to a new Secretary of Defense occurs well in advance of the transition of Chairman of the Joint Chiefs of Staff in September in order to ensure stability within the Department.

I pledge my full effort to a smooth transition that ensures the needs and interests of the 2.15 million Service Members and 732,079 DoD civilians receive undistracted attention of the Department at all times so that they can fulfill their critical, round-the-clock mission to protect the American people.

I very much appreciate this opportunity to serve the nation and our men and women in uniform.

Jim N Mattis

Also Read | Mystery light in California sky sends Twitter into a frenzy

Mattis's departure is not a total surprise for Washington observers. Time and again, especially of late, Trump has followed his gut and ignored Mattis's advice. Trump's decision to pull the 2,000 or so US troops out of Syria was a stunning rebuke to Mattis, who had warned that an early withdrawal from Syria would be a "strategic blunder."

The men have previously clashed on numerous other issues -- including the Iran nuclear deal, which Trump pulled out of in May while Mattis defended parts of it. The Pentagon chief was also against the creation of a separate new branch of the US military called Space Force, but Trump ordered it anyway.

Meanwhile, the biggest deployment Mattis has ordered so far was one to the US border with Mexico, a mission that only has loose military utility and one that critics have assailed as a political stunt.