Many of us have had a recurring nightmare. You know the one. In a fog between sleeping and waking, you’re trying desperately to escape from something awful, some looming threat, but you feel paralyzed. Then, with great relief, you suddenly wake up, covered in sweat. The next night, or the next week, though, that same dream returns.

For politicians of Joe Biden’s generation that recurring nightmare was Saigon, 1975. Communist tanks ripping through the streets as friendly forces flee. Thousands of terrified Vietnamese allies pounding at the US Embassy’s gates. Helicopters plucking Americans and Vietnamese from rooftops and disgorging them on Navy ships. Sailors on those ships, now filled with refugees, shoving those million-dollar helicopters into the sea. The greatest power on Earth sent into the most dismal of defeats.

Back then, everyone in official Washington tried to avoid that nightmare. The White House had already negotiated a peace treaty with the North Vietnamese in 1973 to provide a “decent interval” between Washington’s withdrawal and the fall of the South Vietnamese capital. As defeat loomed in April 1975, Congress refused to fund any more fighting. A first-term senator then, Biden himself said, “The United States has no obligation to evacuate one, or 100,001, South Vietnamese.” Yet it happened anyway. Within weeks, Saigon fell and some 135,000 Vietnamese fled, producing scenes of desperation seared into the conscience of a generation.