It was drizzling rain, and gloomy clouds darkened the surface of the Yalu River separating this Chinese city from its North Korean neighbor.

In a nearby commercial district named after an old Korean kingdom, a group of men distinguishable only by their high cropped haircuts and the pins in their lapels depicting Kim Jong Un’s father and grandfather were acting out a tiny drama with broader implications for President Trump’s foreign policy and the future security of the United States.