I blogged earlier about Eliot Ackerman's Fifth Act, Thinking about it some more--one thing stands out is the reliance on personal connections. In the chaos of our exit from Afghanistan, personal connections were everywhere. Initially it was the personal connection of American soldiers, diplomats, and contractors with those who had worked with them. The Afghani asked their friends to help. As the days passed and the panic spread, Afghanis who had no such history contacted Afghanis who had the connection: a friend of a friend, a cousin, a neighbor.
Once contacted the Americans, like Ackerman, relied on their own connections. An ex-soldier contacted an old comrade still in Afghanistan. As the days passed, the calls for help spread, asking any acquaintance who might have any pull over the Marines at the Kabul airport for help. Sometimes the calls go to the chain of command but those at the gates have more power; the former chair of the Joint Chiefs of Staff is eventually at the mercy of and relying upon the grunt, the lieutenant at the gate.
In the situation, the bureaucratic rules get bent and broken, which I imagine is common in extreme cases.
I also see the whole process is dependent on the internet--the appeals for help may be phoned, but the logistics needed to coordinate the arrival of a group at the appropriate airport gate at the time when the right American is there; they all rely on forms of internet communication: email, Twitter, Slack,
I assume our exit from Saigon back in the day was somewhat similar, but without the internet the connections were much more limited.