With the assurance of a sleepwalker (William T. Vollmann)

Their slave-sister Guthrún, marriage-chained to Huns on the other side of the dark wood, sent Gunnar and Hogni a ring wound around with wolf’s hair to warn them not to come; but such devices cannot be guaranteed even in dreams. As the two brothers gazed across the hall-fire at the emissary who sat expectantly or ironically silent in the high-seat, Hogni murmured: Our way’d be fairly fanged, if we rode to claim the gifts he promises us! . . .—And then, raising golden mead-horns in the toasts which kingship requires, they accepted the Hunnish invitation. They could do nothing else, being trapped, as I said, in a fatal dream. While their vassals wept, they sleepwalked down the wooden hall, helmed themselves, mounted horses, and galloped through Myrkvith Forest to their foemen’s castle where Guthrún likewise wept to see them, crying: Betrayed!—Gunnar replied: Too late, sister . . .—for when dreams become nightmares it is ever too late.

When on Z-Day 1936 the Chancellor of Germany, a certain Adolf Hitler, orders twenty-five thousand soldiers across six bridges into the Rhineland Zone, he too fears the future. Unlike Gunnar, he appears pale. Frowning, he grips his left wrist in his right. He’s forsworn mead. He eats only fruits, vegetables and little Viennese cakes. Clenching his teeth, he strides anxiously to and fro. But slowly his voice deepens, becomes a snarling shout. He swallows. His voice sinks. In a monotone he announces: At this moment, German troops are on the march.

What will the English answer? Nothing, for it’s Saturday, when every lord sits on his country estate, counting money, drinking champagne with Jews. The French are more inclined than they to prove his banesmen . . .

Here comes an ultimatum! His head twitches like a gun recoiling on its carriage. He grips the limp forelock which perpetually falls across his face. But then the English tell the French: The Germans, after all, are only going into their own back garden.—By then it’s too late, too late.

I know what I should have done, if I’d been the French, laughs Hitler. I should have struck! And I should not have allowed a single German soldier to cross the Rhine!

To his vassals and henchmen in Munich he chants: I go the way that Providence dictates, with the assurance of a sleepwalker.—They applaud him. The white-armed Hunnish maidens scream with joy.

From William Vollmann’s Europe Central. 

For the past 100 pages or so, Vollmann has referred to Hitler as the sleepwalker (I’m almost positive that the word Hitler hasn’t been used in the text up until now), and while context has made it clear that this sleepwalker is Hitler, the source of the moniker is only clarified at this point.