This is an open access title available under the terms of a CC BY-NC-ND 4.0 International licence. It is free to read on the Oxford Academic platform and offered as a free PDF download from OUP and selected open access locations. Democracy is often described in two opposite ways, as either wonderfully resilient or dangerously fragile. Both characterizations can be correct, depending on the context. When Democracy Breaks aims to deepen our understanding of what separates democratic resilience from democratic fragility by focusing on the latter. The volume’s collaborators–experts in the history and politics of the societies covered in their chapters–explore eleven episodes of democratic breakdown, from ancient Athens to Weimar Germany to present-day Russia, Turkey, and Venezuela. Strikingly, in every case, various forms of democratic erosion long preceded the final democratic breakdown. Although no single causal factor emerges as decisive, linking together all of the episodes, some important commonalities–including extreme political polarization, explicitly anti-democratic political actors, and significant political violence–stand out across the cases. Moreover, the notion of democratic culture, while admittedly difficult to define and even more difficult to measure, may play a role in all of them. Throughout the volume, the contributors show again and again that the written rules of democracy are insufficient to protect against tyranny. While each case of democratic decay is unique, the patterns that emerge shed much light on the continuing struggle to sustain modern democracies and to assess and respond to the threats they face.