World War I was immediately precipitated by the assassination of Archduke Francis Ferdinand of Austria-Hungary by a Serbian nationalist in 1914. There were, however, many factors that had led toward war. Prominent causes were the imperialistic, territorial, and economic rivalries that had been intensifying from the late 19th cent., particularly among Germany, France, Great Britain, Russia, and Austria-Hungary.
Of equal importance was the rampant spirit of nationalism, especially unsettling in the empire of Austria-Hungary and perhaps also in France. Nationalism had brought the unification of Germany by "blood and iron," and France, deprived of Alsace and Lorraine by the Franco-Prussian War of 1870-71, had been left with its own nationalistic cult seeking revenge against Germany. While French nationalists were hostile to Germany, which sought to maintain its gains by militarism and alliances, nationalism was creating violent tensions in the Austro-Hungarian Monarchy ; there the large Slavic national groups had grown increasingly restive, and Serbia as well as Russia fanned Slavic hopes for freedom and Pan-Slavism .
Imperialist rivalry had grown more intense with the "new imperialism" of the late 19th and early 20th cent. The great powers had come into conflict over spheres of influence in China and over territories in Africa, and the Eastern Question , created by the decline of the Ottoman Empire, had produced several disturbing controversies. Particularly unsettling was the policy of Germany. It embarked late but aggressively on colonial expansion under Emperor William II , came into conflict with France over Morocco , and seemed to threaten Great Britain by its rapid naval expansion.
These issues, imperialist and nationalist, resulted in a hardening of alliance systems in the Triple Alliance and Triple Entente and in a general armaments race. Nonetheless, a false optimism regarding peace prevailed almost until the onset of the war, an...