This chapter examines the long-term and deeper causes of what is called the primordial catastrophe of the twentieth century. It is also concerned with the moods and mentalities and the bearing that these had on the outbreak of war in 1914. The chapter commences with the origins of the First World War. To grasp the highly dynamic developments that the societies of Europe underwent in the three or four decades before 1914, the impact of industrialisation, demography and urbanisation is considered as major background factors. The chapter also discusses social imperialism, electoral politics, cultural optimism, cultural pessimism and the preventive war in 1914. There are two key documents that date from the spring of 1914 after the international and domestic situation in Germany and Austria-Hungary had deteriorated further in 1913. Finally, the chapter talks about the key to understanding what happened in Europe in July and August 1914.