On the occasion of the outbreak of the First World War – 1914-1918: The First World War brought unprecedented brutality, overthrew monarchies, changed maps, encouraged revolts and revolutions. revolts and revolutions. It did not bring real peace. In the words of the former US diplomat George F. Kennan, it was the "primal catastrophe of the 20th century". It cost the lives of at least 17 million people.