This Special Issue examines the ways in which emerging or established social theorists from Continental Europe and the United States were personally and politically involved in and affected by the First the First World War (WWI), and considers how the war shaped their sociological theories. WWI was a pivotal moment that transformed global and historical systems in ways that challenged conventional social scientific assumptions about the supposed shift from "traditional" to "modern" societies and compelled sociologists to reconsider the impact of industry and military affairs on everyday life. The period from 1914 to 1918 has typically been ignored or bracketed by later scholars as a largely inconsequential gap in an otherwise uninterrupted flow of intellectual production. By considering not only individual theorists and their social networks but also the transformation of the discipline as a whole, the contributors to this Special Issue offer a systematic assessment of the relevance of this formative period in the development of sociological theory and of the impact of war in shaping the modern world. The Editors' Introduction highlights how the scale and intensity of the total war that engaged the countries of Europe and North America in 1914 came as a shock to most intellectuals, even though nationalistic wars had become familiar to them from the precious century. The central role of nation-states in carrying out what was at the time was called the European War, and later came to be known as the First World War, made it impossible for social scientists and other intellectuals in the belligerent countries to remain neutral. Even those who were not directly active in or publicly vocal about the war felt compelled to take a stand, and many reached their highest level of public visibility and political influence during the WWI era, often beyond the reputation they achieved before or after. The complex problems emerging within the nation-state system that the war had exposed renewed their sense of professional duty and patriotic loyalty while focussing their attention on questions concerning the geopolitics of international warfare and peace; the role of the modern state and its bureaucratic institutions; the nature of civil society and ethnic communities; the forces of political economy and cultural mobilization; and the emancipatory potential of colonial capitalism and racialized imperialism.