In Standpoint, Judith Wolfe reviews the Black Notebooks.
[H]e pitched the romantic nationalism of Friedrich Hölderlin, who — following Fichte and Hegel — envisioned the Germans as a people called to school the world in a different attitude to the world: a poetic disposition of attentive letting-be that allowed the self to become a "clearing" on which the light of Being might fall and show forth beings as they are. In a gesture of indirect resistance, Heidegger lectured enthusiastically about this Hölderlinian nationalism in Freiburg.
At the same time, the heuristic of "technology" allowed Heidegger to escape the deadlock of competing nationalisms by exposing Nazism as not very special, but in fact quite similar to "Bolshevism" and what Heidegger called "Americanism": another machine for grinding down the rich inner life of the world into a mass of homogenous, useful material.
Here's a head-scratcher: "In the Black Notebooks Heidegger’s misplaced reverence for Being qua “destiny” occasionally reaches absurd proportions. For instance he attributes numinous power to names that begin with the letter H: Heraclitus, Hölderlin, and Hegel. But Hitler would also seem to belong to the list, as would, of course, Heidegger. Heidegger also indulges in baseless numerological prophesizing, conjecturing that a final “decision” (Entscheidung) on the planetary reign of “Americanism” will come to pass in 2300. He also predicts that in the year 2327 his own name will re-emerge from the oblivion of forgetting, that is, on the 400th anniversary of the publication of Being and Time." from Richard Wolin's review of the Black Notebooks.