US Defense Secretary Jim Mattis resigned Thursday after President Donald Trump ordered a complete troop pullout from Syria and a significant withdrawal from Afghanistan.
Trump steadfastly defended his sudden push for retrenchment, vowing that the United States would no longer be the "policeman of the Middle East" and saying the 2,000-strong US force in Syria was no longer needed as ISIS had been defeated.
Mattis, a battle-hardened retired four-star general seen as a moderating force on the often impulsive president, made little attempt to hide his disagreements with Trump.
"Because you have the right to have a secretary of defense whose views are better aligned with yours," Mattis said in a letter to Trump, "I believe it is right for me to step down from my position."
Mattis hailed the coalition to defeat ISIS as well as NATO.
"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," Mattis wrote.
One day after the surprise announcement on Syria, a US official told AFP that Trump had also decided on a "significant withdrawal" in a much larger US operation – Afghanistan.
Some 14,000 troops are fighting the Taliban in Afghanistan as part of the longest-ever US war, launched in response to the September 11, 2001 attacks. The Wall Street Journal reported that more than half would be returning.
Trump privately has been grousing about US military involvement in Afghanistan, telling an ally as recently as Wednesday words to the effect of, "What are we doing there? We've been there all these years."
The source, who asked to remain unidentified, said it appeared the president "has lost all patience" with the US military presence in Afghanistan.
Trump has surrounded himself with former military men and shown an uncharacteristic public deference toward Mattis, a bookish 68-year-old who has disagreed with the president behind the scenes on issues from Russia to Iran to accepting transgender soldiers.
He hinted at Mattis' departure as far back as October, telling CBS: "It could be that he is (leaving). I think he's sort of a Democrat, if you want to know the truth... He may leave. I mean, at some point, everybody leaves."
On Twitter Thursday, however, Trump had only praise for his defense secretary, who will serve until the end of February, crediting him with achieving "tremendous progress."
