The Taliban is sweeping across Afghanistan seizing more than a dozen provincial capitals in the past week, and is poised to seize more. Afghan defense forces, finding themselves mostly cut off from U.S. air support, haven’t been able to stop them, and the Afghan government may not survive for much longer. The United States has all but abandoned the country.

A disastrous Taliban takeover wasn’t inevitable. President Biden said his hands were tied to a withdrawal given the awful peace deal negotiated between the Trump administration and the Taliban. But there was still a way to pull out American troops while giving our Afghan partners a better chance to hold the gains we made with them over the last two decades.

Mr. Biden chose otherwise. The way he announced the drawdown and eventual departure of American troops — at the start of the fighting season, on a rapid timeline and sans adequate coordination with the Afghan government — has in part gotten us into the current situation.

Reasonable people can disagree about the wisdom of keeping American military forces in Afghanistan indefinitely, even at very low numbers. I and others have argued that the investment, including the risk to American personnel, is worth it to prevent militant groups from once again overrunning the country.

Mr. Biden believes that further expending U.S. resources in Afghanistan is “a recipe for being there indefinitely.” He rightly notes that President Trump had left him few good options by making a terrible deal with the Taliban. That’s a fine argument, but it explains neither the hastiness nor the consequences we are now observing: the Taliban overrunning swaths of the country, closing in on Kabul, pushing the Afghan security forces and government to the brink of collapse and prompting the Pentagon to prepare for a possible evacuation of the U.S. embassy.

A responsible withdrawal needed more time and better preparation. History will record Mr. Biden, a supposed master of foreign policy for decades, as having failed in this most critical assignment.

As U.S. military planners well know, the Afghan war has a seasonal pattern. The Taliban leadership retreats to bases, largely in Pakistan, every winter and then launches the group’s fighting season campaign in the spring, moving into high gear in the summer after the poppy harvest. At the very least, the United States should have continued to support the Afghans through this period to help them blunt the Taliban’s latest offensive and buy time to plan for a future devoid of American military assistance.