As king, Frederick William I of Prussia gets credit for having created a strong army and an efficient civil service, but, as a father, he left something to be desired. A crude and violent man, his chief pleasures were hunting, relaxing with his “tobacco parliament” of beer-quaffing officers, and inspecting his soldiers on the parade ground in Potsdam, which he spelled varyingly as Bostdam or Postdam. Book knowledge and cultural pursuits in general he despised as unmanly and “the work of Satan.” In his ledgers, wages for academicians came under the heading of “expenses for the various royal buffoons.” In his zealous frugality, he had fired the court’s castrato singers and its chocolatier and ordered its elaborate silver centerpieces and precious knick-knacks melted into bars to be stashed away in the cellar. He was subject to drastic mood shifts and spells of insanity, brought on by porphyria, a congenital illness which causes multiple swellings and blisters and, to top it off, turns the sufferer’s urine blue.

The brunt of the king’s wrath was borne by Frederick (1712–1786), his eldest son, a precocious boy who preferred books and flute lessons to hunting and military reviews. From an early age, Frederick learned to dissemble—“I would very much like to know what is going on in that little head,” his father noted—but could not hide his fear of gunfire or his clumsiness