Mattis' resignation letter is a sharp rebuke of Trump's 'America First' philosophy

AP Photo/Alex Brandon, File

US Defense Secretary Jim Mattis.

• James Mattis on Thursday stepped down as defense secretary, issuing a brutal resignation letter that stands as a sharp rebuke of President Donald Trump's "America First" philosophy.
• In a letter simply addressed to "Mr. President" and without stating Trump's name, Mattis ripped into the president's bombastic, isolationist approach to foreign affairs.
• Trump has routinely faced criticism for insulting America's traditional allies and Mattis' letter alludes to the president's behavior in this regard.
• Mattis emphasized the need to treat allies with "respect."

"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.

James Mattis on Thursday stepped down as defense secretary, issuing a brutal resignation letter that stands as a sharp rebuke of President Donald Trump's "America First" philosophy.

In a letter simply addressed to "Mr. President" and without stating Trump's name, Mattis ripped into the president's bombastic, isolationist approach to foreign affairs.

"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 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."

Trump has routinely faced criticism for insulting America's traditional allies, particularly the UK, France, and Germany, while going against them on an array of issues - from the Paris climate accord to the Iran nuclear deal.

The president's critics have also taken issue with his habitual verbal attacks against NATO, via which he's made inaccurate claims about the nature of the historic alliance and the way in which it is funded.

In his letter, Mattis alluded to Trump's behavior in this regard, stating, "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."

The retired Marine Corps general added, "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 also seemed to take issue with Trump's embrace of authoritarian regimes and declared friendships with leaders like Chinese President Xi Jinping.

He wrote, "I believe we must be resolute and unambiguous in our approach to those countries whose strategic interests are increasingly in tension with ours."

Mattis said it's "clear" China and Russia "want to shape a world consistent with their authoritarian model gaining veto authority over other nation's economic, diplomatic, and security decisions to promote their own interests at the expense of their neighbors, America and our allies."

He emphasized the US must use all of the "tools of American power" to provide for "common defense" against growing threats from countries like Russia and China.

Mattis toward the end of his letter said, "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."

He is set to leave the Trump administration in February 2019.