Diplomatic rivalries and international crises played key roles in the rush to war, but a complete understanding of the war’s origins requires an account of the attitudes and convictions of Europeans around 1914.1 Widespread militarism and nationalism encouraged leaders and citizens alike to see international relations as an arena for the testing of national power, with war if necessary.

Germany was especially famous for militarism, but military institutions played a prominent role in affairs of state and in the lives of ordinary people across Europe. In a period marked by diplomatic tensions, politicians relied on generals and military experts to help shape public policy. All the Great Powers built up their armed forces and designed mobilization plans to rush men and weapons to the field of battle. Universal conscription in most European nations exposed hundreds of thousands of young men each year to military culture and discipline.

The continent had not experienced a major conflict since the Franco-Prussian War (1870–1871), so Europeans vastly underestimated the destructive potential of modern weapons. Encouraged by the patriotic national press, many believed that war was glorious, manly, and heroic. If they expected another conflict, they thought it would be over quickly. Leading politicians and intellectuals likewise portrayed war as a test of strength that would lead to national unity and renewal. Such ideas permeated European society.

Support for military values was closely linked to a growing sense of popular nationalism, the notion that one’s country was superior to all others. Nationalism drove the spiraling arms race and the struggle over colonies. Broad popular commitment to national interests above all else weakened groups that thought in terms of international communities and consequences. Inspired by nationalist beliefs, much of the population was ready for war.

Political leaders had long used foreign adventurism and diplomatic posturing to distract the people from domestic conflicts. Determined to hold onto power and frightened by rising popular movements, ruling classes across Europe were willing to gamble on diplomatic brinksmanship and even war to postpone dealing with intractable social and political conflicts. Victory promised to preserve the privileged positions of elites and rally the masses behind the national cause. The patriotic nationalism bolstered by the outbreak of war did bring unity in the short run, but the wealthy governing classes underestimated the risk of war to themselves. They had forgotten that great wars and great social revolutions very often go hand in hand.