On Sunday evening in Berlin’s monumental Olympic Stadium, England soccer fans will get an overdose of a Germany that still fascinates many: fascist architecture, muscular statues and the ghost of Hitler’s propagandafest 1936 Olympics. That vanished country’s legacy of brutal militarism was something many Germans feared, exactly 25 years ago, was poised for a comeback. In the summer of 1999, the federal government packed the last of its boxes in Bonn and headed east to Germany’s new, old capital. The so-called Berliner Republik was born. A decade after the fall of the Berlin Wall and German unification, many were curious...