Romantic militarism sometimes merged with romantic nationalism, which exalted the language, culture, homeland, and racial makeup of an ethnic group—the ethos of blood and soil—and held that a nation could fulfill its destiny only as an ethnically cleansed sovereign state. It drew strength from the muzzy notion that violent struggle is the life force of nature (“red in tooth and claw”) and the engine of human progress. (This can be distinguished from the Enlightenment idea that the engine of human progress is problem-sovling.)

Steven Pinker, Enlightenment now: the case for reason, science, humanism, and progress, New York, 2018, p. 165