Contingencies are messy things. The Biden administration’s improvisatory scramble after the fall of Kabul to the Taliban was one of several such messes America witnessed in the final weeks of August. Another was President Joe Biden’s impromptu effort to explain that the shambolic disgrace was among the best possible outcomes. Biden set an artificial deadline and sleepwalked toward it, igniting a frantic effort in which NATO and non-NATO nations engaged to transit as many of their citizens, residents, and terrified Afghan allies as possible out of the country while Biden contracted with the Taliban to provide perimeter security at the Kabul airport. Over 100,000 people got out, but many more were left behind, including American citizens and permanent residents. Biden congratulated himself. “No nation has ever done anything like it in all of history,” he...