How World Order Collapses: Crises Dominos and Collective Security

This article asks how the collapse of a liberal international order unfolds in practice. Existing debates focus on sources of decay – U.S. withdrawal and erratic leadership, the rise of China and relative U.S. decline, democratic backsliding, backlash against economic openness, institutional obsolescence in the face of technological and climate change, and domestic norm contestation. They largely assume, rather than demonstrate, that crises diffuse: shocks in one arena spill across regions and issue areas, triggering cascades that unsettle allied equilibria. I theorise a crisis domino effect as a mechanism of order collapse. When a major crisis such as a U.S–China confrontation erupts, allied responses can take two stylized forms: cohesive, unified decision-making or fragmented, conflictual responses. In a system of complex interdependence, fragmentation in managing one crisis (like a U.S.-China confrontation) reconfigures expectations of resolve, reliability, and coordination in other arenas – such as EU–Russia security relations – increasing the perceived probability and impact of secondary crises. I test this argument through a large-N (=500+) expert vignette experiment. Experts first rate the likelihood and impact of key EU–Russia risks, then receive a U.S.–China crisis treatment, and re-rate the same risks. Randomising EU coherence versus fragmentation in the treatment arm allows us to identify whether allied unity mitigates crisis-induced elevation in threat perceptions.