Nietzsche was a German and he was very well known by the German public befrore and during WW1. Many German soldiers carried small copies of Nietzche with them.
From the H.L. Menken biography of Nietzsche:
There were two other children in the house. One was a boy, Josef, who was named after the Duke of Altenburg, and died in infancy in 1850. The other was a girl, Therese Elisabeth Alexandra, who became in after years her brother's housekeeper, guardian angel and biographer. Her three names were those of the three noble children her father had grounded in the humanities. Elisabeth - who married toward middle age and is best known as Frau Förster-Nietzsche - tells us practically all that we know about the Nietzsche family and the private life of its distinguished son. ((1)) The clan came out of Poland, like so many other families of Eastern Germany, at the time of the sad, vain wars. Legend maintains that it was noble in its day and Nietzsche himself liked to think so. The name, says Elisabeth, was originally Nietzschy. "Germany is a great nation," Nietzsche would say, "only because its people have so much Polish blood in their veins.... I am proud of my Polish descent. I remember that in former times a Polish noble, by his simple veto, could overturn the resolution of a popular assembly. There were giants in Poland in the time of my forefathers."