 In spring 1917, Rau, by this time an elected trade union official in his firm, participated in the attempt to organise a strike against the war.His action led to a reprimand from his employer, and may have hastened his conscription into the army in August 1917.In the army he was trained in the Zuffenhausen-garrisoned Infantry Regiment 126 and deployed to the Western Front as member of a machine gun company.