Introduction

This introduction examines how nineteenth- and early twentieth-century global imperial crises sparked debates over alternatives to dynastic or external rule. While imperial collapse often produced instability and centralizing governments, decentralized – federalist and autonomist – visions emerged as contested alternatives. Although empires resisted federalism due to asymmetrical authority and coercive integration, most modern federations are postimperial or postcolonial, designed to manage diversity, preserve shared economic and social spaces, and enable power-sharing in composite states. The concept of federation circulated globally in four overlapping waves between the 1770s and 1960s. Early federations appeared in the Americas and some European empires (1770s–1830s), followed by mid-century experiments in Switzerland, Canada, Austro-Hungary, and Germany (1840s–1880s). The third wave (1900s–1920s), central to this volume, produced diverse projects across Habsburg, Russian, Qing, and Ottoman empires. The fourth wave (1940s–1960s) arose amid the post-Second World War reconstruction and decolonization. The introduction frames federation as a transformation rather than rejection of empire, redistributing sovereignty vertically and horizontally through territorial and non-territorial autonomy. It highlights the global circulation, localization, and adaptation of federalist and autonomist ideas, revealing alternative trajectories from empires to nation-states and anticipating a potential “fifth wave” aimed at managing diversity in modern federations.