On the day that Afghanistan’s capital fell to the Taliban, delivering the definitive verdict on a war that had lumbered on ambiguously for nearly 20 years, one of the city’s top security officials woke up preparing for battle.

The day before, government forces in the north’s largest city — Mazar-e Sharif, a notorious anti-Taliban stronghold — had surrendered with barely a fight.

The same had happened overnight in Jalalabad, the traditional winter home of Afghanistan’s kings and the country’s main gateway to the east.