An admiral writes of a world leader who is familiar to us: ¡°He is vanity itself, sacrificing everything to his own moods and childish amusements, and nobody checks him in doing so. I ask myself how people with blood rather than water in their veins can bear to be around him.¡±

I cheated by putting my first sentence above in the present tense. These words were, in fact, written in July 1914 by Germany¡¯s Albert Hopman, about Kaiser Wilhelm II. A fellow historian who, like me, has written a book about the outbreak of World War I, messaged recently, asking if I share her view of the character matches between Wilhelm and today¡¯s U.S. president.

I do indeed. And find myself scared by them. Donald Trump¡¯s extraordinary performance in Davos, littered with falsehoods, insults and explosions of grandiloquence, closely resembled one of the Kaiser¡¯s public performances as he rattled his saber in the years before playing a major role in precipitating World War I.