When President Joe Biden appeared in the White House East Room on July 8 to stress that the US pullout from Afghanistan was proceeding apace, he declared that a Taliban takeover of the country was not inevitable.

Five weeks later, the Taliban is in charge, scenes of chaos at the Kabul airport from the evacuation of Americans and US-aligned Afghan citizens has transfixed the world, and Biden is scrambling to defend himself from a series of miscalculations that have damaged US credibility...