Born in Magdeburg, Petry served in the German army during World War I. After the war, he completed his studies with a doctorate in philosophy. To support himself, he worked as a journalist, writer, editor and freelance translator. He published the poetry collections Der ewige Rausch (The Eternal Intoxication) in 1919 and Angst und Erlösung (Fear and Redemption) in 1920. He also explored German Expressionism in his literary work. In 1920, he published Die dadaistische Korruption (The Dadaist Corruption). From 1927, he worked for the Magdeburgische Zeitung.