The sacred union that united France’s political parties during World War I contributed to a resilient morale on the home front. Germany's invasion of France, and the conflict over Alsace-Lorraine in particular, contributed to French concern over atrocities and the national investment in the war effort. New weapons and other fighting technologies, coupled with the widespread use of trenches, made fighting tremendously difficult and gruesome on all fronts. Reading assignment: Sowerwine, Charles. France since 1870: Culture, Politics and Society, pp. 106-118.