In Joseph Roth’s novel of the Austro-Hungarian Empire, “The Radetzky March,” there is an extraordinary scene in which the varied soldiers of that vast, improbable portmanteau parade in Vienna before the Hapsburg emperor, Franz Joseph. Uniformed men stream by, Austrians, Italians, Hungarians, Slovenians, and—most remarkably and most exotically—Bosnians, vivid in their “blood-red fezzes,” which seemed to glow, Roth writes, like bonfires lit by Islam in tribute to the Emperor himself. Those blood-red fezzes are all Roth needs to conjure the distant romance of the Bosnian subjects, who disappear from the novelistic pageant as quickly as they flashed by.