Lernet-Holenia participated in the Invasion of Poland as a reactivated and drafted lieutenant of the reserve, an experience on which he based his 1941 novel Die Blaue Stunde (The Blue Hour) which after the war became known under the title Mars im Widder (Mars in Aries). It has been called "the only Austrian resistance novel" because the plot features an ideologically troubled central character, hints at the existence of active political opposition, and because the Nazi government banned and quarantined the first edition of the book.
Although Lernet-Holenia made himself a lucrative business as a popular screenplay writer during the Third Reich, he was one of the few accomplished Austrian authors who kept his distance from National Socialism, and refused to endorse the Nazi political system or to participate in its notorious blood and soil literary efforts. However, to stay in business he had to make arrangements with the regime, which included becoming chief dramaturgist at the "Heers-Filmstelle" (the audiovisual media center of the Wehrmacht in Berlin, charged with producing propaganda films for military cinemas) after the Polish campaign. Robert Dassanowsky has stated that "[Lernet-Holenia's] early actions in the Reich were confused, appearing to vacillate between naiveté and the often clumsy, often shrewd acts of a survivalist ... a unique but not incomprehensible position." Lernet-Holenia became more outspoken as the war progressed. After his removal from his public position in 1944 he escaped service on the Eastern combat theatre through contrived illness and the help of the resistance network.