Wait, Is the U.S. Allied With the Taliban Against ISIS Now?

There’s an odd historical resonance the fact that Vice President Kamala Harris is visiting Vietnam as the scenes of chaos, bloodshed, and desperation play out in Afghanistan this week. For Americans, the evacuation of Kabul resembles, and has frequently been compared to, that of Saigon 46 years ago. Depending on your political persuasion, both are humiliating surrenders, the inevitable results of American hubris, or some combination of the two. But there may be lessons for Afghanistan’s new rulers as well.

Vietnam’s ruling Communist Party were once seen as such a grave threat to...