The most serious book about the Napoleon obsession was born in a German concentration camp. Early in 1940, the Dutch historian Pieter Geyl wrote an essay on how Bonaparte had been seen by successive generations of French historians and sent it off to a journal for publication. After the German invasion in May, although he had “not written a single word about Hitler”, the piece was returned to him by an editor nervous at implied parallels.

Geyl was too fastidious a scholar to make crude analogies. He would go on to make it clear that “the persecution of the Jews had no parallel in Napoleon’s system”. But when he converted the essay into a lecture that September in Rotterdam, the audience responded with knowing laughter as he ran through the inventory of Napoleon’s failings listed by his French critics: the liquidation of a free press; the emasculation of any meaningful representative institutions; contempt for intellectuals; the ego-fetish of the will in action; the presumption that national glory must necessarily be forged in the carnage of war, and its logical corollary, an insatiable lust for military expansionism; the habit of treating humans instrumentally as grist to his glory mill; the chilly indifference to the loss of millions of lives, especially those of his own troops; an invariable tendency to blame everyone other than himself when things went awry.

However indirect Geyl may have been, the SS came for him, ostensibly as a hostage in retaliation for the mistreatment of Germans in the Dutch East Indies. In Buchenwald, where he spent 13 months, audiences continued to chuckle, but Geyl began drafting what would flower into the masterwork of historiography that is Napoleon: For and Against. Its great motif is that history is an “argument without end”.