When Joe Louis took only 124 seconds to knock out Max Schmeling in 1938, it was one of the most historic sports triumphs of the 20th century.

Schmeling, a reluctant representative of Nazi Germany, had defeated Louis two years earlier, and the Reich’s propagandists had proclaimed that result — Louis’ first professional loss — as a demonstration of Aryan supremacy. The rematch was broadcast in dozens of languages. In dispatching Schmeling, Louis became a hero to a world that trembled before the ascendant Nazi war machine, and the first black man to achieve broad acceptance as a symbolic ambassador for the United States.