It is a measure of Washington’s profoundly anxious condition that Mattis, dismissed as a warmonger during the Obama administration, has been held up in liberal circles as a potential savior. He has mostly tried to keep American policy on autopilot, and that is deeply reassuring to many people who fear Trump’s instincts. In Syria, for instance, Mattis maintained the Obama administration’s military alliance with Kurdish guerrillas in the fight against ISIS and has now expanded it, though without really adjusting for political realities of an emerging Kurdish state. In January, when Tillerson formalized the decision to stay on and expand the mission, he sketched out grandiose goals — pushing back against Iran and Assad and preserving friendships with the Turks — without saying how those conflicting aims could be accomplished. The policy’s contradictions became apparent almost immediately. Days after Tillerson’s announcement, the Turkish military launched a bombing campaign against America’s Kurdish allies, and there is no sign yet of how the administration hopes to reconcile its partners. Something very similar could be said about Trump’s Afghanistan policy, introduced last August: more soldiers, more promises, but no plan to manage the regional power struggles that have kept America tied down for 17 years.

Still, these policies have the virtue of familiarity. The next few months offer the prospect of something frighteningly new. President Trump’s impromptu decision in early March to hold face-to-face talks with Kim Jong-un sets up a host of risks and an almost-impossible timeline. If the talks fail, lower-level diplomatic channels — usually held as a precursor to a leadership summit — could also collapse, raising the chances of war. The talks are now expected to take place by the end of May, the same month in which Trump has promised to abandon the Iran nuclear agreement if a deal is not reached to strengthen it. All this is happening with the State Department still desperately understaffed and in the midst of a transition. Trump, his aides say, is feeling newly liberated to ignore cautious advice, and his nominee for secretary of state, Mike Pompeo, is said to be fully in tune with his rowdier impulses. And on March 22, Trump announced that he was replacing McMaster with John Bolton, the hawkish lawyer who published an op-ed in The Wall Street Journal in February on “the legal case for striking North Korea first.” If events spin out of control, Mattis could be forced to choose between his loyalty to the chain of command and the moral imperative to avert a catastrophic war.