The great Austrian writer Stefan Zweig confided in his autobiography: “I have a pretty thorough knowledge of history, but never, to my recollection, has it produced such madness in such gigantic proportions.” He was referring to Germany in 1923, a “year of lunacy,” defined by hyperinflation, violence, a political system on the verge of collapse, the rise of Adolf Hitler and the Nazi Party and separatist movements threatening to rip apart the German nation. Most observers found it miraculous that the Weimar Republic—the first German democracy—was able to survive, though some of the...