In the beginning, it was not like this. Spreading terror was historically an instrument of state and military policy. When there were only foot soldiers to do it, they might be sent out to kill and rape, more or less at random, in a densely populated town or city either as revenge for some slight or as a lesson designed to cow those who survived into terrified submission. Soldiers terrified people and they created an atmosphere of terror.
The invention of air planes added new possibilities. In the 1920s, Arthur Harris - later "Bomber" Harris of Britain's World War Two Bomber Command - wrote this in a 1924 report from his RAF base in Iraq: