Upon mobilization in August 1914, the Royal Saxon Army became the German Third Army and Hausen was given command. His army participated in the Battle of the Frontiers, mainly in the battles of Dinant, where Hausen's troops summarily executed over 600 of its inhabitants, including several women and children (one of them just 3 weeks old), and Charleroi, and he and his army were responsible for the destruction of Reims in September 1914. When asked about how such deeds would eventually be known into history, he replied: