In 1800, Europeans governed about one-third of the world's land surface; by the start of World War I in 1914, Europeans had imposed some form of political or economic ascendancy on over 80 percent of the globe. The basic structure of global and European politics in the twentieth century was fashioned in the previous century out of the clash of competing imperial interests and the effects, both beneficial and harmful, of the imperial powers on the societies they dominated. This encyclopedia offers current, detailed information on the major world powers and their global empires, as well as on the people, events, ideas, and movements, both European and non-European, that shaped the Age of Imperialism.