It was a split-second decision. Mirza Ali Ahmadi and his wife Suraya found themselves and their five children on Aug 19 in a chaotic crowd outside the gates of the Kabul airport in Afghanistan when a US soldier, from over the tall fence, asked if they needed help.

Fearing their two-month-old baby Sohail would get crushed in the melee, they handed him to the soldier, thinking they would soon get to the entrance, which was only about 5m away.

But at that moment, Mirza Ali said, the Taliban - which had swiftly taken over the country as US troops withdrew - began pushing back hundreds of hopeful evacuees. It took the rest of the family more than a half-hour to get to...