Focusing on the choices made by coteries, this study examines the perplexing question of why World War I happened. In each case, the decision to enter the war was made by a handful of individuals—monarchs, ministers, military people, party leaders, ambassadors, and a few others. In each case also, separate and distinct agendas are seen, with considerations differing from one nation to the next. The leadership of Japan, the Ottoman Empire, Italy, the Balkans, and the United States are explored, as well as that of the major powers involved—Austria-Hungary, Germany, France, and Great Britain,