When war broke out in 1914, Eisner’s friend and employer Adolf Müller, who was a state parliament deputy for the Bavarian Social Democrats and editor-in-chief of the "Münchener Post", the SPD newspaper, took the side of the state and the government. After a brief period in which he joined with supporters of the war, seeing it as a necessary evil in curbing Russian Tsarism, Eisner changed tack and became an outspoken critic. This led Müller to ban him from any involvement in the newspaper’s political section. Up until the January strike of 1918, the only payment Eisner received was for writing freelance theater reviews.
Eisner, writing about Adolf Müller in his 1918 prison diary, said that he had been misled in his initial assessment of the causes of the war “by many years of systematic scheming by an old government socialist”