Defense Secretary Jim Mattis resigned Thursday, seemingly in protest of President Donald Trump's orders to withdraw from Syria and an "America First" policy that appears to discount the value of allies and local partnered forces fighting alongside U.S. troops.
"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 said in his letter of resignation released by the Defense Department.
Trump made a pre-emptive announcement via Twitter late Thursday that Mattis was retiring and would officially step down from the post in February.
The announcement followed on the president's surprise move Wednesday to withdraw U.S. troops from Syria, a move widely seen as a rejection of Mattis' commitment to stand by partnered forces in Syria until a lasting defeat is dealt to the Islamic State.
By late afternoon Thursday, Mattis had yet to issue the official withdrawal order to the troops. Bipartisan members of the House and Senate were rallying support for resolutions urging Trump to reverse his decision.
In his Tweet, Trump said, "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 equipment."
In his resignation letter, Mattis stressed his commitment to alliances and pledges made to partnered forces, suggesting the basis for his dispute with Trump over the Syrian withdrawal.
"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.
In the announcement, Trump made little reference to Mattis' lengthy list of contributions to the nation's defense, first as a career Marine and four-star general and then his two-year tenure as defense secretary, a period during which he revised the National Defense Strategy and strived to improve the readiness and lethality of the services.
Instead, Trump praised Mattis for backing him up in the effort to get NATO allies to spend more on defense.
"General Mattis was a great help to me in getting allies and other countries to pay their share of military obligations," Trump said. "A new Secretary of Defense will be named shortly. I greatly thank Jim for his service!"
In his letter, Mattis said he agreed with Trump that the U.S. military "should not be the policeman of the world," but added that alliances and partnered local forces were the key to U.S. successes in the field following the 9/11 terror attacks.
"The Defeat-ISIS coalition of 74 nations [in Syria and Iraq] is further proof," he said.
During his term, Mattis was viewed by allies as a military professional with a lifetime commitment to the nation's defense who served as a moderating influence on a sometimes impulsive president.
His influence appeared to have waned in recent months, with Trump openly discussing that Mattis might be leaving and suggesting that the secretary might secretly be a Democrat. Mattis responded that he has never been registered with a political party.
In recent weeks, Mattis was said to have favored Air Force Chief of Staff Gen. David Goldfein to succeed Marine Gen. Joseph Dunford as Joint Chiefs chairman, but Trump instead chose Army Chief of Staff Gen. Mark Milley.
Mattis also was said to have harbored doubts about Trump's order to send more than 5,000 active-duty troops to the southern border of the U.S. to help stop the so-called "caravans" of political asylum seekers.
The breakup between the two contrasted with Trump's ebullience two years ago in announcing that Mattis would be his choice for defense secretary. Trump affectionately called him "Mad Dog," a nickname Mattis never held in the Marine Corps and apparently detests.
In his letter, Mattis said he holds beliefs that cannot be compromised. "My views on treating allies with respect and also being clear-eyed about both malign influences and strategic competitors are strongly held and informed by over four decades of immersion on these issues," he wrote. "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."
Mattis went to the White House on Thursday to find out if those beliefs aligned with Trump's, according to U.S. officials who spoke on grounds of anonymity. He then returned to the Pentagon to pen his letter of resignation.
-- Richard Sisk can be reached at Richard.Sisk@Military.com.