During World War I, German troops invaded Belgium, targeting peaceful towns and citizens. They resorted to taking hostages and executing them as a method to instill fear and suppress any potential resistance from the local population. Notably, in Dinant, a horrific massacre occurred where 612 individuals, including men, women, and children, were shot by German soldiers.

The American media characterized these brutal actions as "frightfulness," a term that describes what would later be understood as terrorism. Such atrocities highlighted the severe impact of war on civilians and the lengths to which the occupying forces would go to maintain control, as discussed in Erik Larson's book "Dead Wake: The Last Crossing of the Lusitania."