Answer: Leaders knew that if they declared war, their allies had to join the fight with them.
Explanation: In the late nineteenth century, many industrialized countries forged alliances and agreements that culminated in the year 1914 in World War I. Germany had gone through the process of unification between 1870-1871, making it a strong, industrialized state; German leader Bismarck defeated France in the Franco-Prussian War (1871). With this defeat, France lost to Russia (the state that led the German unification) as regions of Alsace and Lorraine.