The same year, he was drafted, and in 1917, he was gravely injured while he was fighting at the Western Front of World War I,[1] causing him to spend the following period recovering in a military hospital at Heidelberg.

Having previously been a member of Der Stahlhelm, Maurer joined the Sturmabteilung after the Nazi party took control of Germany in 1933, but left the organisation in 1935.

The theory was supported mainly by Tacitus and Pliny the Elder and especially the latter's observation in the Natural History of there being Germanorum genera quinque: "five kinds of Germans".

[5] In the third edition of 1952, Maurer added archaeological evidence to support his classification, most notably citing Rafael von Uslar's article of the same year, "Archäologische Fundgruppen und germanische Stammesgebiete vornehmlich aus der Zeit um Christi Geburt."

His theory has been criticized by later linguists, but they focused mainly on the terms that Maurer used by equating tribes and peoples to language groups and use of nationalistic jargon, which was then considered acceptable.