The preparations for The Birth of Tragedy were interrupted by an event on the world-stage which produced profound and permanent effects on Nietzsche's thinking. Halfway through writing a letter begun on July 16, 1870, telling Rohde what a good impression he had made on the Wagners during his May visit to Tribschen, he heard the news:

This reveals something of Nietzsche's initially confused and ambiguous response to the July 19 declaration of war. On the one hand he is horrified that European culture has failed to prevent the outbreak of war, that it is lapsing into barbarism. But one the other, already perceiving Europe to be a culture in need of regeneration, he sees the possibility of cells of regeneration – ‘monasteries’ – growing up on the ‘wasteland’ left by the perhaps cleansing fire of war. (The ‘monastery’ – or sometimes ‘colony’ – ‘for free spirits’ will soon become a major theme.) That he signs the letter ‘Your true Swiss’ suggests that, taking advantage of Swiss neutrality, he plans to sit the whole thing out.