Our Kurdish allies are being slaughtered. The worst may be yet to come

In the 11 days since President Trump’s tweets announced a sudden exit of US special forces from Northern Syria, greenlighting an armed incursion by Turkish forces emboldened by our precipitous abandonment of the ally who had fought the Islamic State on our collective behalf, we’ve witnessed the wholesale dysfunction of American politics to the detriment of our interests, values, and credibility. It’s gotten worse by the day. The events on Wednesday represented the low watermark at an already low point in American diplomacy.

Consider what we already know: On Sunday night, without warning, the president at last acted on his impulses. Having already arrogantly claimed he knew “more about ISIS than the generals” — and having driven both General James Mattis and Brett McGurk, the US special envoy heading the five-year-old successful global anti-ISIS coalition, to resign — Trump gave Turkey’s President Recep Erdogan the long-sought and long-denied implicit permission to go into Kurdistan and attack his longtime adversaries.

The firestorm from both sides of the aisle was immediate, and the internal damage control effort went into blundering overdrive. From the Oval Office itself, the president dictated the single most embarrassing letter (that we know of so far) in presidential history. At the behest of advisers, to try and ward off Turkish military actions, Trump wrote to Erdogan. He threatened economic ruin for Turkey and urged the strongman, “Don’t be a tough guy” and “don’t be a fool.” He ended this admonition with the bizarre postscript: “I will call you later.” Within 24 hours of Trump’s inexcusable and unmistakable green light, Turkey’s troops rolled into Kurdistan. Why?

Diplomacy is not a shockingly childish letter so bizarre that incredulous journalists had to confirm its authenticity with the White House press office. Diplomacy is a carefully thought-through strategic balancing of interests and artful persuasion. Trump had in fact lost his leverage to influence Turkey long before the letter was sent; he lost it the minute his itchy Twitter finger announced that our troops would stand down.

The costs are manifest, both in bloody, tragic Technicolor and in the halls of foreign ministries everywhere. The blow to our young men and women in uniform — all of them, but especially those on the ground who formed relationships with Kurds and who took pride in the risks they took for our nation — will grate forever. The result is that we all must witness our allies, who fought with us and for us to decimate ISIS, now being slaughtered. Young Kurds who fought next to American soldiers are being killed because of this president. We’re bombing our own bases so they won’t be occupied. Russian President Vladimir Putin and Syrian President Bashar Assad are laughing at us. Some ISIS prisoners, taken off the battlefield and guarded by the Kurds, have escaped, and more may be set free, reigniting the flame of extremism — a direct threat to the United States.

Before long it may be inevitable that we redeploy troops to protect us, only now in a very changed and more complicated strategic environment. American credibility has been shattered in ways unimaginable. Trump’s impulsive seat-of-the-pants Twitter decision-making has sent a message to any country considering a negotiation with us that, when politics or whims intervene, the United States doesn’t keep its word.

Most disturbing, in irony a president ignorant of history and foreign policy clearly doesn’t understand, Trump has made it infinitely harder, if not impossible, for the United States to do what he claims he wants: ask allies to share in the burden of national security. Trump said, “It’s not our border. We shouldn’t be losing lives over it.’’ What he ignores is that we were already losing American lives to ISIS before we went there.

That’s why, starting in 2014, we carefully and methodically built a genuine global coalition against ISIS among allies, Persian Gulf neighbors, and even regional rivals who had different worldviews and entrenched rivalries. We brought more than 68 countries together to destroy ISIS. The coalition always depended on balancing competing agendas and interests and suspicions. That’s called diplomacy. It worked. Regional partners, including the Kurds, did much of the fighting so that we didn’t have to put enormous numbers of boots on the ground in a “forever war.” They stepped up. Who now will ever step up again if the reward is abandonment?

Congratulations, Mr. President: You just made it more likely that a future president will face the awful decision of whether to go back in, with fewer countries by our side.

And now? Instead of forcing a change of course, even the president’s Republican critics seem to be grudgingly falling in line and resuming their reflexive defense of every indefensible action of a reckless and ignorant commander in chief. They applaud him for imposing sanctions on Turkey that Erdogan will ignore. Sanctions? It’s a deeply cynical example of the arsonist calling the fire department as the building is burning to the ground and expecting credit. As an editorial in The Economist stated, it’s a charade in which “a flailing superpower has turned to economic sanctions to pretend it is still relevant.”

But that’s what a president can do when his political allies do little more than tweet criticism themselves. On Wednesday, the president insulted all our Gulf partners: “They’ve got a lot of sand over there. So, there’s a lot of sand that they can play with. . . . Let them fight their own wars.’’ Then in a meeting with congressional leaders, he insulted General Mattis, his own former defense secretary, as “overrated.” The reaction from House Republicans? They attacked House Speaker Nancy Pelosi.

Senate Republican leader Mitch McConnell publicly questioned ‘‘what tools do we have’’ to make Trump change course? Well, respectfully, when a president — facing an impeachment inquiry and dependent on his Senate allies to stay in office — subverts American values on foreign policy, I’d think the majority leader has quite a bit of leverage over the president’s behavior on an issue so fundamental to who we are. As the president threw a tantrum, maybe that was a moment for McConnell and House minority leader Kevin McCarthy to paraphrase Trump’s message to Erdogan: “Don’t be a fool. . . . I will call you later.”

The world watches the reality show in the White House in horror. But the greatest horror may be yet to come: What must be going through minds of other front-line US partners in far-flung places like Taiwan, staring across the strait at more assertive China, or the Baltics, on the frontier of a newly emboldened Russia? Even if the cease-fire holds, the damage is done. What conclusions are being drawn about US resolve or willingness to stand with our partners in peril? It’s all too real, and so too is our political dysfunction that’s not stepping up to stop it.

John F. Kerry, a visiting distinguished statesman at the Carnegie Endowment for International Peace, represented Massachusetts in the US Senate for 28 years and was US secretary of state from 2013 to 2017.