The resignation of American defense secretary James Mattis has shocked European allies, who were counting on the former Marine Corps general to protect them from the whims of President Donald Trump.

Mattis stepped down when Trump unexpectedly ordered the withdrawal of American troops from Afghanistan and Syria, where they act as a buffer between American-allied Turkey and American-backed Kurdish militants.

But in his resignation letter, Mattis pointed to wider disagreements with the president — on the need to maintain strong alliances and to be “resolute and unambiguous” toward China and Russia, which “want to shape a world consistent with their authoritarian model.”

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.

Trump, by contrast, has consistently disparaged NATO allies, called America’s security commitment to Europe into question, squandered America’s moral leadership and aligned himself with Russia’s Vladimir Putin.

Reactions from Europe

• Peter Altmaier, German economy minister: “This is deeply sad.”
• Carl Bildt, former Swedish foreign minister and co-chair of the European Council on Foreign Relations: “A morning of alarm in Europe. Sec Def Mattis is the remaining strong bond across the Atlantic in the Trump Administration. All the others are fragile at best or broken at worst.”
• Ank Bijleveld, Dutch defense minister: “Terrible.”
• Tobias Ellwood, British veterans ministers: “Our world will be less safe.”
• Alan Posener, British-German political analyst: “Trump betrays everyone: the Israelis, the Kurds, the Europeans.”
• Libération (France): “In disagreement with Trump, Pentagon chief slams the door.”
• Der Spiegel (Germany): “Trump makes the chaos complete.”
• Süddeutsche Zeitung (Germany): “The last bastion of reason falls.”
• NRC (Netherlands): “Mattis wipes the floor with Trump’s foreign policy.”
• El País (Spain): “Pentagon chief resigns in public public controversy with Trump over Syria.”
• The Independent (UK): “Mattis resignation over Trump foreign policies sparks panic.”