In the early twentieth century, educated Europeans had good reason to believe that they were living in an age of progress. The ongoing triumphs of industry and science and the steady improvements in the standard of living beginning about 1850 were undeniable. There had also been progress in the political realm. The bitter class conflicts that culminated in the bloody civil strife of 1848 had given way in most European countries to stable nation-states with elected legislative bodies. Moreover, there had been no general European war since 1815. Only the brief, limited wars connected with German and Italian unification at midcentury had broken the peace in the European heartland.

In the global arena, peace was much more elusive. In the name of imperialism, Europeans (and North Americans) used war and the threat of war to open markets and punish foreign governments around the world. These foreign campaigns resonated with European citizens and stimulated popular nationalism. Thus imperialism and nationalism reinforced and strengthened each other in Europe, especially after 1875.

This was a dangerous development. Easy imperialist victories over weak states and poorly armed non-Western peoples encouraged excessive pride and led Europeans to underestimate the fragility of their accomplishments as well as the murderous power of their weaponry. Imperialism also made nationalism more aggressive and militaristic. At the same time that European imperialism was dividing the world, the leading European states were also dividing themselves into two opposing military alliances. Thus when the two armed camps stumbled into war in 1914, there would be a superabundance of nationalistic fervor, patriotic sacrifice, and military destruction.