We now know that President Joe Biden was offering only dark jest when, eight months ago, his inaugural address pledged to “repair our alliances … and be a strong and trusted partner for peace, progress, and security.”

On Tuesday, we learned that the president would not extend an Aug. 31 deadline for the evacuation of all U.S. persons and allies from Afghanistan. The failure to extend that deadline reflects a forensic betrayal of American credibility and honor and of our commitment to allies.

The devil is in the details.

This is a betrayal of Britain and other European allies whose soldiers fought and died alongside Americans. These allies are already enraged by what they regard as an overly cautious and politicized U.S. posture at Kabul’s airport. True, only America could secure this airlift out of Kabul. But at a G-7 virtual summit on Tuesday, allied leaders begged Biden to extend the deadline. He wasn’t listening.

The Taliban thus have every reason to continue their escalating obstruction of evacuations from Kabul’s airport. It is now eminently possible that some Americans will be abandoned to medievalist evil . It is almost certain that Afghan allies will be left behind. Those who interpreted alongside, spied for, and otherwise served America now witness an America they do not know.

Let’s be clear about something else: The president needn’t have made this terrible decision. He has accepted the Taliban’s threat and knelt before it. Instead, Biden could and should have made clear to the Taliban that the United States would not leave until all those who America and its allies needed to evacuate were saved. He could and should have enforced his demand that the Taliban tear down their roadblocks and facilitate an orderly evacuation.

Biden has the means to make these messages credible.

The airport is defensible . U.S. air supremacy would allow the military to impose devastating costs on Taliban forces in and around Kabul — costs, that is to say, sufficiently significant to bring questions as to the credibility of the Taliban’s new emirate. The group craves internal political legitimacy that comes only with the apparatus of sovereign power. It would almost certainly choose a comprehensive allied evacuation that lasts a matter of weeks over the risked annihilation of its ministries, leaders, and more capable forces — a loss that undermines its theologically vested claim to represent God’s sovereign power on Earth.

Alas, no. Biden’s unmoved deadline will boost the Taliban’s growing confidence that it holds a stranglehold over the strategic initiative. The president has made it more not less likely that the Taliban will escalate its obstruction of the evacuation. Biden has made it more not less likely that the Taliban will enable or otherwise tolerate attacks on the airport by its Haqqani network allies or even its erstwhile nemesis, the Islamic State. The perception of American weakness is fuel to the jihadist fire. And Biden has just delivered a supertanker’s worth of it.

The wreckage of this disaster is not limited to Afghan borders. Biden’s gross betrayal of U.S. allies matches his total disregard for the message his betrayal sends to America’s global foes. Indeed, Biden has done nothing to deter the Taliban from restoring a safe haven for its al Qaeda ally.* That safe haven is coming .