Conscription is a policy that requires individuals to serve in the military or other form of national service. It has been an important part of many states’ military strategy and national defense throughout the centuries. This chapter aims to provide a comprehensive understanding of conscription and its implications for societies and states across Europe in the early twenty-first century. Drawing on academic literature, the authors examine the phenomenon through a multidimensional lens, integrating the historical evolution of conscription, different theoretical approaches, forms, and determinants. The review synthesizes findings from key studies and presents a nuanced understanding of the evolution of conscription, its theoretical frameworks, forms, and determinants. This chapter also outlines the methodology of the international comparative research conducted in six European countries (Estonia, Finland, Lithuania, Norway, Sweden, and Switzerland). Data on conscripts collected between 2021 and 2022 are analyzed in subsequent chapters of the book. This chapter provides the methodological background, including the quantitative survey instrument, sampling, and key characteristics of the respondents. Finally, the chapter describes the structure of the book and gives brief descriptions of each chapter.