The fog of war is proverbial. Combat against unconventional enemies, who mix with the civilian population, makes it challenging to tell friend from foe. For U.S. forces trying to extricate themselves and allies from Kabul last month, these difficulties were compounded by the environment and the context: a city of 4.4 million in which Islamic State-Khorasan terrorists took cover and, on Aug. 26, struck, killing 13 U.S. service members and scores of Afghans.

Even with those caveats, the Aug. 29 drone-launched missile attack against a suspected terrorist target in Kabul ranks as a horrible potential error for the United States. Initially portrayed by Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, as a “righteous strike” on an Islamic State vehicle being prepared as a car bomb for another attack against U.S. troops, the incident now appears far more likely to have been a deadly case of mistaken identity.

What U.S. aerial assets tracked and ultimately destroyed was probably a U.S.-based charity’s vehicle driven by Zamarai Ahmadi, an aid worker. Investigations by The Post and the New York Times raise serious questions about the U.S. military’s claim that the weapon used, a single Hellfire missile, triggered a “secondary explosion” indicative of a car loaded with explosives. Rather than explosives, Mr. Ahmadi seems to have been loading the car with water canisters for his family. Rather than the three civilian deaths so far acknowledged by the Pentagon, the true toll may be 10, including Mr. Ahmadi and seven children ranging in age from 3 to 16.

The Pentagon says it is continuing to investigate. Definitive judgment must await the results. If, as seems all too probable, the eyewitness testimony and expert analysis gathered by journalists stands up, the United States must offer both sincere apologies and generous compensation to surviving family members of the victims.

There must also be a clear-eyed assessment about what this episode implies for the “over the horizon” approach to terrorist threats in Afghanistan that President Biden has adopted now that U.S. troops — and a friendly Afghan government — are gone. Mr. Biden has long portrayed remotely based forces as a smart, low-cost means of coping with hostile forces that have grown more diffuse and no longer must be countered with American boots on the ground. Common sense, however, dictates that his alternative creates risks of its own.

Drone strikes would be at the heart of Mr. Biden’s strategy. By definition, much of the information to guide those strikes would be gathered by aerial reconnaissance and analyzed at installations hundreds or even thousands of miles away. The United States would not rely on troops or intelligence officers on the ground, whether our own or those of allies.

At the margins, this could reduce the United States’ ability to identify targets, lower the chances of hitting real targets and raise the chances of killing innocent ones. As William J. Burns, the director of the Central Intelligence Agency, acknowledged in congressional testimony April 14: “When the time comes for the U.S. military to withdraw, the U.S. government’s ability to collect and act on threats will diminish. That is simply a fact.” The apparent tragedy in Kabul underscores that reality — and the need for the Biden administration to act on it.